GEOLOGIJA 39, 13-77 (1996), Ljubljana
Ontogenetic development of dentition in the cave bear
Ontogenetski razvoj zobovja pri jamskem medvedu
Irena Debeljak
Ivan Rakovec Institute of Palaeontology,
Scientific Research Centre of the Slovenian Academy of Sciences and Arts,
Gosposka 13, SI-1000 Ljubljana, Slovenia
Key words: Ursus spelaeus, Ursidae, dentition, jawbones, ontogenetic develop-
ment, growth, age determination, sex dimorphism, mortality, Divje babe I
Ključne besede:Ursus spelaeus, Ursidae, zobovje, čeljustnice, ontogenetski raz-
voj, rast, določanje starosti, spolni dimorfizem, mortaliteta. Divje babe I
Abstract
In this contribution the ontogenetic development of dentition in the cave bear
{Ursus spelaeus Rosenmüller & Heinroth) is described up to the age of about four
years, when the animals became adult and the formation of their teeth was complet-
ed. The process of tooth growth and the replacement of deciduous teeth by perma-
nent dentition took place in a similar way as with the present-day brown bear
{Ursus arctos Linné). The teeth eruption sequence is the same in both species.
The specimens of cave bear jawbones that served for this study were collected
from the well-known Palaeolithic site Divje babe I (W Slovenia). Individual age
estimations of these jawbones were made on the supposition that a certain ontoge-
netic stage in the development of cave bear dentition corresponds to an approxi-
mately equal age of an individual as with the brown bear. The growth of the jaw,
however, was essentially faster in cubs of the cave bear We also presume that the
secondary sex dimorphism in cave bears with males having larger jawbones than
females was already expressed in the first year of life.
With regard to some indices, especially after noting the obvious discordance
between the expected and actually observed mortality profile, we should also con-
sider another possibility; that ontogenetic development in the cave bear was signifi-
cantly slower than in present-day bears. However, this alternative does not seem
very probable, because a proper ontogenetic development has its functional impor-
tance. A long time iag in the eruption of permanent molars would mean a certain
disadvantage to the species.
Kratka vsebina
V prispevku je opisan ontogenetski razvoj zobovja jamskega medveda {Ursus
spelaeus Rosenmüller & Heinroth) vse do starosti približno štirih let, ko so živali
odrastle, njihovi zobje pa so bili dokončno formirani. Proces rasti zob in zamenjave
mlečnega zobovja s stalnim je pri jamskem medvedu potekal na podoben način kot
14_Irena Debeljak
Introduction
In contrast w^ith the phylogenetic evolution, the ontogenetic evolution of cave bear
dentition has not been explicitly described so far, and it is generally little known to
the professional public.
Most researchers of the cave bear limit themselves to the statement that a certain
jawbone is juvenile, which means that it belonged to a cub. Only seldom do the
authors (as Rädulescu & Samson, 1959) accompany the photographs or
descriptions with more detailed information on the age of the cub. The latter can be
estimated by comparison with the present-day brown bear In the present work all
data on teeth eruption in the brown bear are collected that are important for deter-
mining the individual age of juvenile jawbones of the cave bear and of other bear
species as well.
The reason for interest in the age determination of relatively rare juvenile jawbone
finds is not simple curiosity. Palaeontologists and archaeologists are also interested in
the behaviour of cave bears and the environment in which they lived, especially
including the relationship between prehistoric man and bear From this point of view,
the precise assessment of individual ages of jawbones that belonged to cubs less than
one year old offers us very important information, i.e. on the season in which the ani-
mals died.
By all means, the most accurate data on cave bear mortality can be achieved by
the age analysis of single, isolated teeth found in tens of thousands in those Palae-
olithic cave sites that had also served as typical dens of the cave bear. The individual
age of particular juvenile teeth can be correctly estimated, however, only after previ-
ous study of their development and degree of formation at various ages on the set of
the whole jawbones.
Exactly this was the primary reason for our analysis of the jawbones of cave bear
cubs from the Palaeolithic locality Divje babe I. This study was the basis for our fur-
ther research on the age structure of the cave bear population from the upper part of
the Pleistocene deposits (Debeljak, 1996a, 1997). The age analysis was carried out
on isolated deciduous teeth d^ and permanent teeth М^. Therefore in the present
paper a more detailed description of the ontogenetic development of these teeth is
given.
pri današnjem rjavem medvedu {Ursus arctos Linné). Zaporedje izraščanja zob je pri
obeh vrstah enako.
Primerki čeljustnic jamskega medveda, na katerih je opisan ontogenetski razvoj
zobovja, so iz znanega paleolitskega najdišča Divje babe I (W Slovenija). Individual-
no starost teh čeljustnic smo ocenili glede na domnevo, da določena ontogenetska
stopnja v razvoju zobovja jamskega medveda ustreza približno isti starosti osebka
kot pri rjavem medvedu. Rast čeljusti pa je bila pri mladičih jamskega medveda
vendarle bistveno hitrejša. Domnevamo tudi, da je bil pri jamskih medvedih sekun-
darni spolni dimorfizem izražen že v prvem letu življenja; samci so imeli večje čelju-
sti od samic.
Glede na nekatere pokazatelje, še posebej po očitnem razhajanju med pričako-
vanim in dejansko ugotovljenim mortalitetnim profilom, bi morali upoštevati tudi
drugo možnost; da je bil ontogenetski razvoj zobovja jamskega medveda bistveno
počasnejši kot pri današnjih medvedih. Vendar, ta alternativa se ne zdi zelo verjetna,
ker ima primeren ontogenetski razvoj svoj funkcionalen pomen. Dolg časovni zaosta-
nek pri izraščanju stalnih molarjev bi za vrsto pomenil določeno pomanjkljivost.
Ontogenetic development of dentition in the cave bear_15
Previous research
Ehrenberg was the first to study the ontogenetic evolution of the cave bear He
established the identity of the ontogenetic stages of dentition with those of the brown
bear (1931, 640). He described the different steps in the development of mandibles,
and he approximately estimated their individual ages (1931, 659-675, 701-703). In
those times only scarce data were available on tooth growth in the brown bear, so it is
understandable that Ehrenberg's age estimates were imprecise. He concluded that
in the well-known locality Drachenhöhle near Mixnitz many remains belong to cubs
that perished from exhaustion prior to spring - less than 4 months old. According to
Ehrenberg, this age-class was followed by a long gap after which appeared the
group of most numerous remains of cubs about 1 year old. The supposed mortality
peak at that age was explained as the consequence of complications in eruption of the
last, i.e. distal molars. Ehrenberg's interpretation of the presumed absence of
remains of 4-10-month-old cubs was that cave bears occupied caves only in winter,
during hibernation. This opinion has prevailed among researchers until the present
day. Former spectacular ideas of cave bear hunting were withdrawn by sober scientif-
ic judgement.
After 30 years Ehrenberg obtained good comparative data for the present-day
brown bear He attributed the age of 7 months to an almost complete skeleton of a
cave bear cub from Hartlesgraben (1964, 217-219). In the same contribution he cor-
rected age estimates of certain mandibles made in 1931. Nevertheless, he remained
convinced about the existence of the above-mentioned gap in the age composition of
the cave bear remains while explaining the rare remains of 4-10-month-old cubs as
an exception that confirms the rule.
Musil (1965, 72) sorted the juvenile jawbones of cave bears from the Pod hradem
cave according to their progressive ontogenetic development, and described them in
detail. However, he did not determine their individual ages.
Material and methods
The ontogenetic development of cave bear dentition will be described on eleven
examples of jawbones from the Palaeolithic site Divje babe I, which is located below
the edge of the plateau Šebreljska planota, above the Idrijca River valley (W Slove-
nia). The larger part of Pleistocene deposits in the cave originate from the Middle
Würm period. All fossil cave bear remains from the Divje babe I are kept in the
National Museum of Slovenia in Ljubljana. General information on the locality can
be found in Turk et al., 1989a, b and Turk ed., 1997.
Age estimations of individual jawbones were made according to Dittrich's
(1960) comprehensive data set on present-day bears, and the comparisons with juve-
nile jawbones of the brown bear from Slovenia. The sex was determined from the size
of the teeth, especially of canines, according to the works of Koby (1949) and
Kurten (1955).
Some facts on the living habits of the brown bear that can also be attributed to its
relative the cave bear are summarized from Macdonald ed., 1985, 88-95 and
Krystufek, 1991, 191-193.
16_Irena Debeljak
Jawbones and teeth of the cave bear - general
The lower jaw of bears consists of two mandible bones (i.e. hemimandibles or
mandibles). They are joined in a symphysis that never ossifies. The upper jaw is
formed on each side by two paired bones: the premaxilla that bears the incisors and
extends to the canine, and the upper jawbone or maxilla. These two bones are fused
only in grown up individuals. In jawbones tooth sockets or alveolae appear in which
tooth roots are attached.
The brown bear as well as the cave bear have in both jaws on each side the follow-
ing deciduous teeth: 3 incisors (dil-3), one canine (dc) and usually 3 premolars (d2-4
or p2-4). On each side of the lower jaw of the cave bear the following permanent teeth
are present: three incisives (I1.3), one canine (C), usually a single premolar (P^) and
three molars (M^g). In the maxilla there is one molar less.
The molars have a broad masticatory surface with numerous low, rounded cusps.
Early researches into the morphology of dentition and the skull revealed that the cave
bear was almost exclusively vegetarian in habits (cf. Kurten, 1976). Recent isotopie
analyses confirmed this hypothesis (Bocherens et al., 1994).
The permanent dentition of bears was described in detail by Rode (1935). Ko by
(1952) and Rädulescu and Samson, (1959) described the deciduous dentition of
the cave bear
For the orientation of jawbones and teeth a variety of terms is used. In this paper
the following terms are met: Front - anterior - mesial. Back - posterior - distal. (This
is simplified! The listed terms are not equivalent generally.) Side facing the cheeks -
buccal - lateral. Towards the tongue - lingual (in the mandible) or palatal (in the
maxilla). The biting (upper) surface or edge of the teeth is called occlusal.
The ontogenetic development of dentition in bears (familiy Ursidae)
Certain data on the eruption of permanent teeth in present-day bears can be found
in the following references: Pohle, 1923; Couturier, 1954; Rausch, 1961; Marks
and Erickson, 1966. However, the most detailed study of the development of decid-
uous dentition and its replacement by permanent teeth in the brown bear was done
byDittrich (1960). He established that this process is practically the same and also
synchronous in other bear species. The succession of eruption of individual teeth from
the gums is presented in figure l.Dittrich's other data on the ontogenetic develop-
ment of dentition in bears can be summed up in the following principal points:
The cubs are born toothless. The first milk teeth start erupting during the second
month of life, and they come into position during the third month. The first perma-
nent molars start piercing through the gum in the fifth month of life. The cubs are
able to chew solid food only after they get the first pair of permanent molars
(М^&М^). The deciduous dentition has almost no functional meaning in chewing. The
deciduous teeth are shed by the end of the 15th month. The eruption of the last perma-
nent teeth is accomplished at a mean age of one year and a half.
Dittrich (1960, 119-123) found out that the body weight in bears generally does
not influence the growth and the rate of eruption of teeth. Also individual differences
in this process are relatively small (see fig. 1).
The disposition of deciduous and permanent teeth in the jaws of a brown bear cub
is illustrated by figs. 2a and 2b.
Ontogenetic development of dentition in the cave bear
17
Fig. 1. Ontogenetic development of dentition in the brown bear up to the age of 16 months (after
Dittrich, 1960, 86, fig. 27). Individual deciduous teeth (left) are marked with a dotted pattern,
and permanent teeth (right) with black. An arrow at the beginning or at the end of the symbols
indicates the period in which the start of eruption of milk and permanent teeth, or shedding of
milk teeth could take place. The length of the arrow therefore illustrates individual differences
SI. 1. Ontogenetski razvoj zobovja pri rjavem medvedu do 16. meseca starosti (po Dittrichu,
1960, 86, si. 27). Posamezni mlečni zobje (levo) so označeni pikčasto, stalni zobje (desno) pa s
črno barvo. Konica na začetku in koncu simbolov nakazuje obdobje, v katerem lahko pride do
začetka izraščanja mlečnih in stalnih zob oziroma do izpada mlečnih zob. Dolžina konice torej
ponazarja individualne razlike
The ontogenetic development of dentition in the cave bear
The first three months
Osteological remains of unborn animals (fetuses) and of those cubs v^ho died at
birth or shortly thereafter (neonates), are preserved only exceptionally in the Pleis-
tocene localities. Nevertheless, such finds are not so rare in the Divje babe, because
the cave served for long millenia as a den, especially to cave bear females who
whelped their young in the winter months from December to February (Turk et al.,
1989b; Debeljak, 1997). The thin and fragile (owing to porosity) mandibles of still
unborn or newborn bears are 2-3 cm long and only around 5 mm wide.
Cave bear young were born toothless. The same is true in present-day bears.
Already in the first week of the brown bear's life, the germs of deciduous teeth can be
18
Irena Debeljak
Fig. 2a. X-ray photograph of the skull of an approximately four-month-old brown bear cub from the Pyrenees
(after Couturier, 1954, 142, PL 30). The individual age was estimated after Dittrich's (1960) data. Natural size
SI. 2a. Rentgenski posnetek lobanje približno štiri mesece starega rjavega medveda s Pirenejev (po Couturieru,
1954, 142, tab. 30). Ocena starosti po Dittrichovih (1960) podatkih. Naravna velikost
Ontogenetic development of dentition in the cave bear
19
Fig. 2b. Schematic illustration of fig. 2a (modified after Couturier, 1954, 143, PI. 30). Small letters mark decidu-
ous teeth, and capital letters permanent teeth
SI. 2b. Shematska ponazoritev slike 2a (prirejeno po Couturieru, 1954, 143, tab. 30). Male črke označujejo mlečne
zobe, velike črke stalne zobe
20_Irena Debeljak
found in preparations of their jaws: small, hollow caps of crowns that had not yet
erupted from the gums (Dittrich, 1960, 11, figs. 1, 2). This neonatal phase of the
ontogenetic evolution is represented by the following example:
1. (PL 1, figs. 1, 2) - Left and right mandibles of two neonates which died in the
first days after birth: For the sake of clarity the mandibles in the illustration (PI. 1,
fig. 1) are joined in their natural position, although they did not belong to the same
individual. In the lateral view (PI. 1, fig. 2), the body of the mandible appears semicir-
cularly curved, which is typical for neonates. On the broken upper surface, the germs
of both deciduous canines are clearly visible, and even the germ of the protoconid of
the last deciduous tooth d^ or p^, as marked by some researchers. (The protoconid is
the central, largest cusp on the mentioned tooth). The germs of deciduous teeth were
originally enclosed in the bone. At that time the alveolae through which the growing
milk teeth would later erupt were still forming. The length of the described mandible
was around 4 centimeters, the same as in the newborn cubs of the brown bear
Ehrenberg (1973) documented the find of an almost complete neonatus skeleton
of about 10 days of age from the Austrian locality Salzofenhöhle. After various mea-
surements and reconstruction that were made with the bones he concluded that the
young of the cave bear could have been only minimally larger at birth than those of
the brown bear. In a brown bear litter there are usually two or three cubs of the size of
a rat, weighing only 350-400 grams. They are hairless, blind and entirely helpless.
They are not able to maintain their body temperature, so they can survive only with
their caring mother in a den protected from the cold.
In the second and third months of life the cave bear cubs most probably stayed in
the den, i.e. in the cave. The female did not leave them. During the long months before
the advent of spring she lived only on fat reserves collected during the late summer
and autumn. For her young this was the time of lactation, of an exclusively milk diet.
Meanwhile, all the deciduous teeth gradually erupted from the gums. Below them,
hidden in the bone, the crowns of the permanent teeth were forming and strengthen-
ing. The eruption sequence of individual deciduous teeth can be reconstructed with
the help of data on the brown bear (fig. 1). This period of ontogenic development is
represented by the following two examples:
2. (PI. 2, figs. 1-3) - The mandible of a cub about 2-2.5 months old: The crown of
the first permanent М^ molar is already formed; on the x-ray photograph (PI. 2, figs.
2, 3) it is clearly visible as a thin, hollow shell encased in the jawbone. Also the first
millimeters of the root wall started growing. Within the mandible the tips or crown
germs of P4 and C are hidden. The permanent teeth developed in hollow chambers of
the mandible with thin partitions in between. On the upper side of the mandible, in
the place where М^ would later erupt, a narrow fissure is open. In front of it appear
small holes; these are alveolae in which the roots of the deciduous premolars d^ and
dg were anchored. They indicate that the mentioned milk teeth had already erupted
from the jawbone, so the cub most probably was not younger than two months. The
mandible was approximately of the same length as in an approximately four-month-
old brown bear (fig. 2a), but much more robust.
3. (PI. 3, figs. 1-3) - Both halves of the mandible of a cub about 2.5-3 months old:
The furrow broadened in the place where in a month or two М^ would start erupting.
Observed from above, the dark crown of М^, fragile like an egg shell, is visible
through it. The upper quarter of the М^ root was already formed (PI. 3, figs. 2, 3); it is
as thin as paper however Also the crowns of the permanent incisives and the germs of
C and P4 teeth are concealed in the jawbone. On the upper side of the mandible the
Ontogenetic development of dentition in the cave bear_21
The fourth to sixth months of life
By the fourth month the bears already have all the deciduous teeth in place. The
more or less formed crowns of the permanent teeth are meanwhile enclosed in the
jawbones, where they gradually strengthen. For example, below the deciduous tooth
d4 there is already the crown of the permanent P^ in a four-month-old cub (figs. 2a,
2b). With the progressive growth of its root the permanent tooth starts protruding and
replacing the milk one. In this process, the strong protoconid of the P^ crown wedges
between the two halves of the d^ root, and it gradually induces the contact resorption
of the root. A similar result also occurs in the upper pair of the deciduous d'^ and per-
manent P"*.
During the fifth month, the first permanent molars (Ml) start erupting. First the
frontal part of the М^ tooth with protoconid and paraconid appears from the gums,
and soon afterwards the posterior part of the crown with metaconid and talonid
(Dittrich, 1960, 80-81). The dentition of the brown bear cub in fig. 2a is in the stage
just described. Couturier (1954, 142-143) published this x-ray picture of a cap-
tured cub, and attributed an age of three months to it. According to Dittrich's
(1960) data it is, however, evident that this cub was in fact older, at least 4 months of
age.
Rädulescu and Samson (1959, 211, fig. 11) published a photograph of the
mandible of an approximately 4-month-old cave bear Musil (1965, 72, Pl. 3, fig. 10)
presented a specimen of the mandible that belonged to a possibly somewhat younger
cub. A picture of a cave bear jawbone that would be typical for a five-month-old cub
(Mj or М^ in the eruption phase) has not yet been found in the literature.
In the osteological collection from the Divje babe I site there is no jawbone of a 4-
to 5-month-old cub available that would be fit for publication. As a matter of fact,
this is not a mere chance, since among the very numerous isolated deciduous teeth
only very rare specimens were found that could be attributed to this age class. (Such
are, for example, the upper or the lower d4 with strengthened root which is already
somewhat resorbed at the apex. Individual cusps on the crown are rounded, and often
bear tiny wear facets. Debeljak, 1996 a, 1997). Evidently the mortality of four- to
five-month-old cubs in the Divje babe cave was much lower than at the younger age.
The present contribution does not intend to discuss possible reasons for varying
mortality rates during the year. It should only be mentioned that the fourth to sixth
month of life was the time of spring. The brown bear cubs accompanied by their
alveolae of deciduous teeth are clearly visible. At this age almost all the deciduous
teeth were in place, although they are not preserved here in this specimen. (The
process of the eruption of milk teeth can be illustrated on an example of d4: at the age
of 1-2 months the crown of d^ was enclosed in the jawbone; the crown was brown in
color, dull and very fragile. Soon afterwards first the tip of the protoconid, i.e. the
cusp that first breaks through the gum, became lighter colored, and later also the
remaining part of the crown. In 2- to 3-month-old cubs the crown of the completely
erupted d^ was already strengthened, normally bright, and with enamel of character-
istic lustre. The root was, however, still hollow, and consequently rather fragile.)
The mandible described is approximately of the same size as in a half-year-old
brown bear. The sketch of an essentially smaller mandible of a three-month-old pre-
sent-day brown bear, as published by Pohle (1923), can serve for comparison.
22_Irena Debeljak
The seventh and eighth months of life
Summer finally arrived. For the whole bear family came the time of intensive
feeding. In the following months they had to collect a sufficient amount of fat, neces-
sary for survival through the next winter The dentition of 6-8-month-old cubs were
then in the following condition:
4. (PI. 4, figs. 1-5) - The mandible of a female approximately 6-7 months old: Con-
siderable progress is evident, as compared to the specimen discussed earlier (PI. 3).
The crowns of all the permanent teeth are already formed. Later they would not grow
any more, but only become stronger with the secondary dentine which was gradually
filling their interior The M-^ of this cub has been "in place" for a month or so, and it
has more than 4/5 of the crown developed. The crown is moderately strengthened, but
the root is still entirely hollow and open at the apexes (PI. 4, fig. 5). M,^ shows the first
signs of wear, which indicates that the animal had already chewed hard food for some
time. As a consequence of chewing numerous tiny wear facets developed, showing a
characteristic glossy surface. It is obvious that the ontogenetic development of the
individual teeth progressed at different rates, in accordance with the data for the
brown bear presented in fig. 1. The М^ surpassed the other permanent teeth in devel-
opment. It is followed by 1^, which was at that time already in place, but is not pre-
served here. I2 emerged through the gum shortly before the cub died. P^ and were
just prior to the eruption phase. The tops of their crowns are already of lighter color.
The last incisor I3 is still enclosed in the mandible, and can be seen only on the x-ray
photograph. The same applies to the canine that has only the crown, but not yet the
root. In this phase of growth, P^ was pushing the overlying d^ and dg deciduous teeth
from the jaw. Their roots were at that time already strongly resorbed. At the latest in
a month or so d^ (not preserved in our specimen) would fall out in a natural way with
an entirely resorbed root. (In bears, the last deciduous premolar d^ is in use for a short
period only. It takes part in chewing solid food for only about 3 months, therefore its
occlusal surface is scarcely ever heavily worn away.) The size of the described
mandible corresponds to a brown bear cub about one year old (PI. 9, fig. 1; PI. 10, fig. 2).
Are our age estimates correct? Was the development of dentition in the cave bear
faster, or perhaps slower than in the living brown bear? Let us discuss this problem
with reference to the example of the above described mandible:
It is physiologically necessary that in the sixth or at least in the seventh month the
ontogenetic development results in the inclusion of the first pair of permanent molars
in dentition. This is valid for the present-day brown bear, and could not have been
much different for the cave bear As already mentioned, during the transition to solid
plant food the most important part is assumed by the first permanent molars Ml. The
mother's milk gradually ceases to suffice for growth, and the cubs have to start feed-
ing on solid food, too. The deciduous teeth, with the exception of the last d4 premo-
mother leave the den after the third month, in April or May, at times as late as the
beginning of June. The same practice was probably true of the cave bear
In addition to the milk sustenance that they get from their mother, the living bears
also begin to chew solid food, starting at the fifth or sixth month. This becomes possi-
ble only after they get the first pair of permanent molars (Dittrich, 1960, 14-15).
The small, pointed milk teeth are of little use for chewing. Only the new back-teeth
can provide the necessary mastication surface.
Ontogenetic development of dentition in the cave bear 23
lars, are so tiny that they have practically no functional importance for chev^^ing hard
plant food (Dittrich, 1960, 14-15, 50, 81-82).
The age of the described mandible of the cave bear, therefore, cannot differ much
from our estimate. In the case of a much higher age, with its chewing surface
would not be "in place" soon enough to enable adequate feeding, so that the growing
cub could make the best use of the summer and autumn food supply. On the other
hand, the size of the mandible and the wear of that could not be caused by mere
milk nutrition testify against a lower age. Perhaps this could be proven by isotopie
analyses of dental tissues.
In my opinion errors in the age estimates are not large, and certainly not essential.
I consider that concerning the ontogenetic development of cave bear dentition, the
comparison with the brown bear is appropriate.
5. (PI. 5, figs. 1, 2) - The mandible of a male bear about 6.5-7.5 months old: The
size of the mandible is almost equal to that of a brown bear at the age of a year and a
half (PI. 16, figs. 1, 2; PI. 18, fig. 1). The anterior part of Mg protrudes out of the jaw-
bone. The enamel becomes lighter in color during this process. In the canine the wall
of the root has just started forming. The crown of Mg is enclosed in the ascending
mandibular branch (i.e. ramus mandibulae), and is consequently of typical dark
brown color, without lustre. A thin bone wall above Mg is broken, so it can be
observed that the occlusal surface is turned lingually (inwards, towards the tongue),
and it stands almost vertically with the anterior part oriented downward. Only after
subsequent growing of the jawbone would the space for the two distal molars be cre-
ated. (In bears, Mg rotates 90° in two directions in order to be included in the tooth
row, while the jaw grows to accommodate it.)
6. (PI. 6, figs. 1-4) - The mandible of a female about 6.5-7.5 months old: The jaw-
bone belonged to a cub of a similar age as in the previous case, it was possibly only a
trifle older. М^ was for a time "in place" and in use. For this reason its crown bears
shallow wear facets approx. up to 3 millimeters in size. The root wall is almost
entirely formed, but still open at the ends (PI. 6, fig. 4). More than half of the Mg
crown already protrudes from the mandible, and about one half of the root is formed.
Its wall is very thin, and the interior hollow (PI. 6, fig. 4). The М^ root is more devel-
oped and firm; the wall is about one millimeter thick. In the same phase of the onto-
genetic development or at the same age, the last lower Mg molar has no root at all,
and the thin, flat crown of this tooth could easily be broken in pieces (cf. Pl. 5).
It is quite obvious that individual teeth of the same cub were developed to various
stages, they were, therefore, of varying mechanical resistance, and consequently did
not have equal possibilities to be preserved as fossils. In analyses of various isolated
teeth we should take into account different degrees of taphonomic losses. Such differ-
ences occurred either as a result of the diverse shapes and sizes of individual teeth, or
owing to various degree of ontogenetic development, which meant unequal firmness
at a certain age.
It is interesting to compare the mandible sizes in plates 4-6 (and also 11-15). Nor-
mally, the size of the bone depends upon the age of the individual. However, it is
noticeable that the mandible size can be rather variable at a similar age as well - in
proportion to the size of permanent teeth. The latter occupy practically the entire
jawbone, as can be clearly seen on the x-ray photographs. Larger dentition also
requires more space. The following conclusions can be made:
1. The cave bear had markedly larger sized dentition than the present-day brown
bear It is understandable that its jaws had to be much larger and more robust in the
24_Irena Debeljak
same ontogenetic phase and age. Although the cave bear cubs were as small at birth
or perhaps only minimally larger than those of the brown bear, the growth of their
jaws in the following months was essentially faster For instance, it was indicated
that the mandible of a cave bear hardly much older than half a year (PI. 5) can be of
the same size as that of a one-and-a-half-year-old brown bear Was the rest of the
body also that much larger? Most probably one cannot reckon with such a rapid
growth of the body mass in cave bear cubs. The female could hardly breed two or
even three such big cubs during the first half-year when their diet was predominantly
milk. It is more probable that the cubs had distinctly large jaws. Therefore, the
jaws/body ratio must have been essentially higher than in adult cave bears, and larg-
er than in brown bear cubs. Confirmation of this supposition is found in the only
extant precisely described and measured skeleton of an approximately seven-month-
old cave bear cub (finds of this kind are extremely rare!). The author of the article,
Ehrenberg (1964, 243-244), was surprised to discover that the facial part of the
skull was much larger than one would expect with regard to the cranium, short trunk
and weak thorax. The reconstruction revealed that at a total length of 60 cm and
height of 30cm more than one third was occupied by the head (Ehrenberg, 1964,
223). It seems that the most probable reason for such a "disproportion" was the func-
tional development of dentition that must have been as fast as with the present-day
brown bear During this process the jawbone size was consequently adapted to the
growing dentition.
2. Cave bear males have on the average larger teeth than females. This holds espe-
cially for the canines, according to the size of which the sex can be determined
(Koby, 1949; Kurten, 1955). In cubs the wide crown base and its growing root
occupy a very large part of the jawbones. It is clear in x-ray photographs that the
height and thickness of the mandible body at a particular age clearly depend pre-
cisely on the size of the canines. Numerous specimens from the Divje babe indicate
that in the same ontogenetic phase the mandibles of females are smaller and more
gracile than those of males. Accordingly, it could be inferred that sexual dimorphism
in cave bear mandibles was already manifested during the first year of life. We must
also consider another possibility: that the development of permanent dentition in
males lagged behind that in females. However, if such differences existed at all, they
could have not been essential for the above-mentioned reason: the young must get
their permanent teeth in place at a certain age to be able to feed properly. Also in pre-
sent-day bears no important differences between the sexes were observed in the
process of teeth growth during the first year (Dittrich, 1960; Marks &Erickson,
1966, 393).
At least one example will represent the upper dentition:
7. (PI. 7, figs. 1-3) - The premaxilla and maxilla of a male approximately 6.5-7.5
months old: both bones are not fused at this particular age. In present-day bears they
become inseparable in adult animals - after the 4th year (Marks & Erickson,
1966, 398-400). The М^ crown shows the first signs of wear According to the shape of
the alveola, P* must have been just in the eruption phase; most of the crown probably
already protruded out of the jawbone. Of the incisors only I^ is preserved. Shortly
before the cub died it had probably already pierced the gum with the tip of its crown.
The tooth socket of the I^ root is not damaged, which permits the observation on the
completed eruption of the tooth. By contrast, the narrow aperture of the I^ alveolus
proves that the eruption of this incisive had not yet started. Above this alveolus the
shallow alveolus of the deciduous di^ is also preserved; at that age the tooth was still
Ontogenetic development of dentition in the cave bear _25
From the ninth month to the end of the first year
During the 9th or 10th month the bears finally get the second lower Mg molars.
The last upper М^ molars start erupting in the ninth month. Sometimes after only the
tenth month the permanent canines begin to pierce through the jawbone. Shortly
in the gum, but would have dropped out of the gum in a month or so. The upper
canine is hidden in the maxilla. In the x-ray photograph (PI. 7, fig. 3) it can be seen
that its root had not yet started to form. The crown is hollow and is still situated
much below, or better, above the rim of the upper jawbone. The deep root socket of
the deciduous eye-tooth is entirely preserved and separated completely by a soHd
bone wall from the developing crown of the permanent canine. Therefore we presume
that the root of the deciduous canine in this phase of the ontogenetic development
still did not display signs of contact resorption.
Before we end the description of ontogenetic development in the seventh and
eighth months of life, another curiosity should be mentioned: Among the juvenile
jawbones from the Divje babe I, most specimens belong precisely to the age period
being discussed, although according to other researchers (Ehrenberg, 1931, 1964;
Kurten, 1958, 1976) the remains of 7-month-old cubs that died in the middle of
summer must have been a real rarity. The general conviction of the last few decades is
that the massively preserved remains of the cave bear in typical Pleistocene cave sites
are of animals that died of exhaustion during long hibernation - in winter and mostly
just before spring. However, also the analysis of isolated d^ and teeth (Debeljak,
1996 a, 1997) indicated that a remarkably high proportion of the fossil population
belongs to cubs that perished presumably at an age of 6-8 months, between July and
September The Divje babe as a typical cave bear site does not represent any excep-
tion. Such results about the age structure of the fossil population are therefore sur-
prising and unexpected. We could explain them in two different ways:
a) Our age estimates of the individual jawbones (and consequently also of isolated
juvenile teeth) are not correct, and the most frequent age group of 7-month-old ani-
mals actually represents those cubs that died during their second hibernation. In this
case, the ontogenetic development of cave bear dentition should lag as much as 6
months behind the ontogenetic development that was ascertained for present-day
bears. According to the feeding habits and needs in the first year (that were described
before), this seems to be almost impossible. On the other hand, in favour of the suppo-
sition above, the appearance of the first thin cementum deposit on the root of the
7-month-old cave bear cubs could be mentioned. This cementum layer was explained
as the "neonatal zone" (Debeljak, 1996a, 29-30, PI. 26-28), but it is very similar to
the following "winter" increments.
b) The other possible interpretation of the discordance between the expected and
observed mortality profile is that our age estimates are correct. Life habits and the
mortality of the cave bear are then different than was thought so far. (Similarly,
Musil (1965, 74-76), after measuring long bones of extremities, came to the conclu-
sion that cave bears kept visiting the cave Pod hradem and also died there in the sum-
mer months.)
Perhaps the final answer will be given by further researches into the ontogenetic
development in present-day bears from different environments, and by detailed
analyses of the dental cementum in bear cubs.
26_   Irena Debeljak
From one year to one and a half years
In bears, during the period between one year and one and a half years the eruption
process of permanent dentition comes to an end. The individual differences become
more pronounced (Dittrich, 1960), thus the age determinations are less accurate
than for the previous period. The last permanent teeth (М^, Mg and canines) are usu-
ally completely erupted in the present-day bears of one and a half years old.
This period of ontogenetic development in the cave bear is represented by the fol-
lowing three examples. Their individual ages were estimated according to the data
for present-day brown bears. Nevertheless, we should also consider the other possi-
bility of slower ontogenetic development of dentition in the cave bear In this case,
the next three mandibles could belong to two-year-olds or even older cubs that died
during their third winter
8. (PI. 11, figs. 1, 2; PI. 13, fig. 1) - The mandible of a male approximately 12-15
months old: The mandible size was equal to that of the adult present-day brown bear
The symphyseal part, where the left and right mandibles were joined, is most proba-
bly pathologically deformed. The inflammatory alteration was possibly the result of a
traumatic lesion of the jaw. About a centimeter and a half of the canine crown pro-
trudes out of the alveolus, and more than half of the root wall is formed already. The
anterior part of the chewing surface of Mg is slightly worn out. A large part of the Mg
crown had not yet erupted through the gum. Its position is still inclined with respect
to the tooth row.
before the completed first year (11th or 12th month) the Mg teeth also appear through
the gum. Owing to the inclined position and remarkably flat crown much time is
needed before they become erupted entirely.
Ehrenberg (1931, Pl. 120, fig. 6) published a photograph of a mandible of a cave
bear cub to which an age of approximately 8-9 months could be ascribed.
Plate 8, fig. 1 and plate 10, fig. 1 show the lower jawbone of an approximately 10-
month-old present-day brown bear from Slovenia. The anterior part of the Mg is
"out". The tips of the permanent canines have just appeared out of the alveola, but
have not yet penetrated the gum. Lateral-distal from them the deciduous canines are
attached. All the other milk teeth were shed before the tenth month.
The mandible in plate 9, fig. 1 and plate 10, fig. 2 belonged to an approximately
one-year-old brown bear from the Kočevje region (S Slovenia). Somewhat more than
1 cm of the canine reaches above the rim of the mandible. Beside it the deciduous
canine with a worn out crown and strongly resorbed root is still in place. For a certain
period during replacement of their canines the bears have the permanent and the
deciduous canines in their gums at the same time. The deciduous canines are shed at
an age of 12-15 months only, during hibernation in the den.
The above two examples of brown bear mandibles are shown here owing to the
lack of an appropriate mandible for the age period being considered in the collection
from the Divje babe. A well-defined gap was observed among isolated teeth (М^) as
well. It appears that the Divje babe I site contains scarcely any remains of cave bears
that died between the 10th month and the completed first year of life, i.e. during the
first part of wintering in the cave den (Debeljak, 1996 a, 1997).
However, with regard to the previous discussion, it is also possible that this "miss-
ing" age-group represents the juveniles of the next summer period.
Ontogenetic development of dentition in the cave bear_27
During the eruption of the last lower Mg molar it sometimes happened that its
crown became wedged with the adjacent Mg crown. On some adult cave bear
mandibles corresponding pathologic changes can be observed that most certainly
caused serious troubles to the animals. According to certain authors the irregularities
in eruption of the last molars were the main, or at least a very important cause of
mortality in cubs during their second winter (Ehrenberg, 1931; Abel, 1931). The
investigations at the Divje babe, however, did not confirm this assumption. I believe
that the difficulties mentioned could have seriously endangered cave bears mostly
later in their lives. Although it was also possible that the eventual infection in a
weakened cub sometimes terminated even with its death.
9. (PI. 12, figs. 1, 2; PI. 13, fig. 2) - The mandible of a female about 15 months old:
Two thirds of the canine root are already formed. The crown has not yet erupted
entirely. It extends for more than two centimeters beyond the margin of the alveolus.
Mg is not yet "in place" or in the occlusal plane. The P^ and Mg roots are still open at
the ends. The root canal of М^ is sealed and the crown "polished", with individual,
2-3 mm wide attrition facets. Wear is also evident on the anterior part of Mg. On the
chewing surface of Mg, however, no traces of wear are visible. Owing to lack of space
in the tooth row the individual teeth pressed one against the other (After the first
year the facets started appearing at points of contact between certain teeth, and they
widened and deepened with time. This is especially pronounced on the anterior wall
of the Mg crown, and the posterior wall of the М^ crown. This type of wear is called
approximal wear, in contrast to occlusal wear on the chewing surface).
For comparison the mandible of the nearly one-and-a-half-year-old brown bear
from the surroundings of Kočevje can be taken (PI. 16, figs. 1, 2; PI. 18, fig. 1). Here,
too, the canines are not yet entirely erupted. However, the tooth roots are already
closed, with the exception of the Mg and canines. The Mg crown has not yet fully
emerged from the gums. The following individual is also in a similar ontogenetic
phase:
10. (PL 14, figs, 1, 2; PL 15, figs. 1-3) - The mandible of a female cave bear approx-
imately one and a half years old: The canine is somewhat more developed than in the
brown bear just discussed. Its crown is practically entirely erupted, only about one
centimeter of the root is lacking. The Mg is in place in dentition. The М^ is somewhat
more worn out as in the above-discussed specimens. The surface is smoothened and
covered with small wear facets. At the point of contact of М^ and Mg a well developed
facet appeared on both teeth (approximal wear). On the posterior wall of the М^
crown this facet is more than 4 mm wide. The М^ root (tooth canal) has already closed
during the first year At the age of around one and a half years its wall was about
2.5-2.75 mm thick. At the Mg the tips of the root were still somewhat perforated. The
Mg root is still widely open, and its wall is very brittle (PL 15, fig. 3).
Isolated teeth have usually been defined as juvenile if the root is open, or as adult
if the root is closed. In this way, certain teeth of the same individual are determined as
adult, and others that lag behind in development as juvenile. The problem, however,
is not only in the uncertainty of the data. The classification mentioned is inadequate
first of all because a large proportion of cub teeth are incorrectly attributed to adults.
The bear becomes adult around the fourth year only. The М^ root closes before the end
of the first year, and the Mg and P^ at an age of one and a half years. Therefore, the
closure of the root apices (or pulp canals) can be a criterion for determining adult sta-
tus only in the last, most distal molars and canines.
As co-author I am obliged to call attention to an error in a paper from five years
28_Irena Debeljak
Further development of dentition and jawbones:
Presumably in the middle or at the end of the second year of life the cave bears
already had the complete permanent dentition erupted. Nevertheless the teeth con-
tinued their development. The originally hollow roots and crowns became more and
more filled with dentine. Finally, in the center only a narrow canal and the pulp
cavity at the passage from root to crown were left. We assume that in the cave bear
during the 4th year the last tooth roots also became sealed: those of the М^, Mg and of
canines. The initially explosive growth of jaws in the following years gradually
slowed down.
11. (PI. 17, figs. 1, 2; PL 18, fig. 2) - The mandible of a subadult male about 4 years
old: The age of this specimen was determined by counting the growth lines (i.e. incre-
ments) in dental cementum. The method is regarded as the most objective, and it is
generally used for estimating the individual ages of wild animals (more in: Debeljak,
1996a, b). The above-mentioned process of dentine deposition in the interior of the
teeth is already at an advanced stage, as clearly seen in the x-ray photograph (PI. 18,
fig. 2). The М^ crown is the most worn out (especially the protoconid and hypoconid),
Mg less and Mg very little so (PI. 17, fig. 2). At the contact of individual molars rela-
tively deep facets developed. On the posterior wall of the М^ crown such a facet is
already more than 6 mm wide. The length of the crown in this way could not be
exactly measured any more. According to the x-ray picture the canine and Mg roots
are not yet completely closed, although they are near to it. In present-day bears the
canine root becomes closed around the 4th year (Marks & Erickson, 1966, 395,
397), i.e. during the time when they reach adulthood.
The above described mandible had not yet reached its final size. The mandibles of
fully grown males measure 5-10 cm more in length. The growth of jaws therefore also
continued after the fourth year In the present-day black bear the head of males
grows during the first 8 years, while in females the growth is terminated somewhat
earlier, soon after reaching sexual maturity (Marks & Erickson, 1966, 400-402).
Most probably it was not much different in cave bears either
Conclusion
In this contribution the ontogenetic development of dentition in the cave bear, and
bears in general, was presented. The process of replacement of deciduous dentition
and the eruption of permanent teeth is generally completed by the age of one and a
half years. Until then the particular ontogenetic phases are a good indicator of indi-
vidual age.
On the basis of the cases described and the data collected the age of juvenile cave
ago, when the ontogenetic development of dentition in bears was not yet sufficiently
known to us (Turk et al., 1992). In that contribution the measurements of "adult"
molars were statistically analyzed with the aim of establishing the ratio of the two
sexes in the adult population of cave bears. In fact, however, the teeth examined
should be attributed to older juveniles (two years, three years, possibly at most four
years old). Their root was closed, and on the ground of this criterion we wrongly
attributed them to adults.
Ontogenetic development of dentition in the cave bear_29
Acknowledgements
I am much obliged to Ivan Turk, the leader of excavations at the Divje babe I, for
the material he ceded for examination. The excavation has been carried out by the
Institute for Archaeology at the Scientific Research Centre of the Slovenian Academy
of Sciences and Arts. At the Clinic for surgery and small animals of the Veterinary
Faculty in Ljubljana, the x-ray examination of jawbones of the cave and brown bear
bear jawbones can be quite accurately estimated. In the future the ontogenetic devel-
opment and the criteria for determining the individual age of particular (isolated)
teeth that are the most numerous and most informative fossil remains of the cave bear
will have to be presented in detail.
Here are the principal conclusions:
- The process of tooth growth and of the replacement of deciduous dentition with
the permanent type took place in the cave bear in the same way, through the same and
probably also synchronic ontogenetic phases as in the related present-day bears.
- It is possible to infer that a certain ontogenetic phase of dentition development
corresponds to approximately the same age of an individual in the cave bear, as well
as in the brown bear The development of dentition in the cave bear must not have
significantly lagged behind, since cubs at a certain age (in the 6th or at least in the
7th month of life) needed the first pair of permanent molars (М^ & М^) to be able to
start chewing hard plant food.
- This argument speaks against another possibility, that the ontogenetic develop-
ment of cave bear dentition was in fact esentially slower than in present-day bears.
Such a characteristic would (in certain circumstances) endanger the existence of the
species. Nevertheless, this alternative still cannot and should not be simply rejected.
- The size of the jawbones during the first year of life (and also later) was depen-
dent upon the sizes of permanent teeth that were developing during that time, partly
encased in the jawbones and almost completely filling them up.
- The growth of jawbones in cave bear cubs was essentially faster than in the pre-
sent-day brown bear Already at the age of one year their mandible was of the same
size as in the adult brown bear This most certainly does not mean that the rest of the
body was also larger to the same degree.
- It is presumed that in the cave bear the secondary sexual dimorphism was mani-
fested already in the first year of life; males had larger sized jaws than females.
- The generally used criterion of distinguishing teeth as juvenile if their crown is
open, and adult when it is closed, is not adequate for most of the cave bear teeth. The
bear becomes adult at the age of around four years. The root, however, closes as
early as the first year of life (after the 8th month), most of other teeth by the age of
one and a half years, and only the roots of М^, Mg and canines at about four years.
- In the study of juvenile jawbones from the Divje babe I site the fact cannot be
overlooked that the majority of the specimens originally belonged to presumably
about seven-month-old cubs that therefore died in the middle of summer This is in
contradiction with the prevailing opinion that massive remains in typical cave bear
localities are of animals that perished owing to exhaustion during hibernation, prior
to spring.
- An interesting problem and task for the future will be to prove and explain this
statement with further researches and additional data.
30_Irena Debeljak
Ontogenetski razvoj zobovja pri jamskem medvedui
Uvod
Za razliko od filogenetskega razvoja ontogenetski razvoj zobovja jamskega med-
veda do zdaj še ni bil pregledno in nazorno opisan in je v strokovni javnosti na sploš-
no slabo poznan.
Večina raziskovalcev jamskega medveda se omeji le na podatek, da je neka čelju-
stnica juvenilna, oz. da je pripadala mladiču. Le redki avtorji (kot npr. Radulescu
& Samson, 1959) fotografije ali opise opremijo z natančnejšim podatkom o starosti
mladiča, ki jo lahko ocenimo s pomočjo primerjave z današnjim rjavim medvedom.
Tokrat so o izraščanju zobovja rjavega medveda zbrani vsi tisti podatki, ki so pomem-
bni za ugotavljanje individualne starosti čeljustnic mladičev jamskega medveda in
tudi drugih medvedjih vrst.
Pri tem ne gre samo za to, da bi ob razmeroma redkih najdbah juvenilnih čeljust-
nic določali starost že davno poginulih živali zgolj iz radovednosti, kot nekakšno za-
nimivost. Paleontologe in arheologe zanima tudi vedenje jamskih medvedov in okolje,
v katerem so živeli, predvsem pa odnos med pračlovekom in medvedom. S tega stališ-
ča nam natančna ocena individualne starosti čeljustnic manj kot leto dni starih mla-
dičev ponuja zelo pomemben podatek: to je sezono, ko so živali poginile.
Seveda nam najbolj natančne podatke o mortaliteti jamskega medveda omogoča
starostna analiza posamičnih, izoliranih zob; v tistih paleolitskih jamskih najdiščih,
ki so bili hkrati tipični brlogi jamskega medveda, jih najdemo v desettisočih primerk-
ih. Vendar, individualno starost posamičnih juvenilnih zob lahko pravilno ugotovimo
le, če njihov razvoj oziroma stopnjo formiranosti pri različni starosti najprej preuči-
mo na nizu celih čeljustnic.
Ravno to je bil povod za analizo čeljustnic mladičev jamskega medveda iz pale-
olitskega najdišča Divje babe I. Ta študija je služila kot osnova za nadaljnjo raziskavo
starostne sestave populacije jamskega medveda iz zgornjega dela pleistocenskih sedi-
mentov (Debeljak, 1996 a, 1997). Starostno analizo smo izpeljali na izoliranih mleč-
nih zobeh d^ in stalnih zobeh М^, zato je v tem prispevku najbolj podrobno predstav-
ljen prav njun ontogenetski razvoj.
was kindly allowed, and performed professionally thanks to the efforts of the veteri-
narians Teodora Ivanuša, Janez Štubelj and Gregor Frelih. Andrej Bidovec (Veteri-
nary Faculty, University in Ljubljana) and Ciril Štrumbelj (Breeding and hunting
ground "Medved", transi. "Bear", Kočevje) provided skulls of present-day brown
bear cubs from Slovenia that were necessary for comparisons. Vida Pohar reviewed
the manuscript. All others who were of whatever assistance in the elaboration of this
paper are also warmly thanked.
Ontogenetski razvoj zobovja pri jamskem medvedu_ 31
Dosedanje raziskave
Ontogenetski razvoj pri jamskem medvedu je prvi preučeval Ehrenberg. Ugo-
tovil je, da so stopnje ontogenetskega razvoja zobovja prav takšne kot pri rjavem
medvedu (1931, 640). Opisal je posamezne razvojne stopnje spodnjih čeljustnic in pri-
bližno ocenil njihovo individualno starost (1931, 659-675, 701-703). V tistem času so
bili na voljo le skopi podatki o rasti zobovja pri rjavem medvedu, zato je razumljivo,
da so bile Ehrenbergove ocene starosti nenatančne. Sklenil je, da v znanem naha-
jališču Drachenhöhle pri Mixnitzu veliko ostankov pripada mladičem, ki so poginili
od izčrpanosti, stari manj kot 4 mesece, tik pred nastopom pomladi. Tej skupini naj bi
sledila izrazita vrzel in potem najštevilčnejši ostanki približno enoletnih mladičev.
Višek smrtnosti pri tej starosti naj bi bil posledica težav pri izraščanju zadnjih kočni-
kov. Po domnevni odsotnosti ostankov 4- do 10-mesečnih mladičev je Ehrenberg
sklepal, da je jamski medved uporabljal jamo le pozimi, v času hibernacije. Takšno
mnenje je med raziskovalci prevladovalo vse do danes. Nekdanje spektakularne pred-
stave o lovu na jamskega medveda so se umaknile trezni znanstveni presoji.
Čez 301etjeEhrenbergže imel dobre primerjalne podatke za recentnega rjavega
medveda, in je skoraj popolnemu skeletu mladiča jamskega medveda iz Hartlesgrabna
pripisal starost 7 mesecev (1964, 217-219). V istem prispevku je popravil ocene starosti
nekaterih mandibul iz leta 1931. Še vedno pa je vztrajal pri svojem prepričanju, da v
starostni sestavi ostankov jamskega medveda obstaja omenjena časovna vrzel, in da so
redki ostanki 4-10-mesečnih mladičev zgolj izjema, ki potrjuje to pravilo.
Musil (1965, 72) je juvenilne čel j ustnice jamskega medveda iz jame Pod hradem
razvrstil po napredovalem ontogenetskem razvoju in jih podrobno opisal. Ni pa jim
natančneje določil individualne starosti.
Material in metode
Ontogenetski razvoj zobovja pri jamskem medvedu bo v nadaljevanju opisan na
enajstih primerih čeljustnic iz paleolitskega najdišča Divje babe I. Jama leži pod ro-
bom Šebreljske planote, nad dolino Idrijce (W Slovenija). Večidel pleistocenskih jam-
skih sedimentov izvira iz obdobja srednjega würma. Vse fosilne ostanke jamskega
medveda iz Divjih bab hrani Narodni muzej Slovenije v Ljubljani. Splošne podatke o
najdišču najdemo v naslednjih delih: Turks sodelavci, 1989a, b in Turk ed., 1997.
Pri oceni starosti posameznih čeljustnic sem si pomagala z izčrpnimi D it tri ch-
ovimi (1960) podatki za recentne medvede in s primerjavo juvenilnih čeljustnic rja-
vega medveda iz Slovenije. Spol sem določila po velikosti zob, predvsem kaninov, gle-
de na ugotovitve Kobyj a (1949) in Kur ten a (1955).
Nekatera dejstva o življenjskih navadah rjavega medveda, ki jih lahko pripišemo
tudi sorodniku jamskemu medvedu, sem povzela po naslednjih delih: Macdonald
ed., 1985, 88-95 (slovenski prevod istega dela: Macdonald ed., 1996) in Krystuf ek,
1991, 191-193.
Čeljustnice in zobje jamskega medveda - splošno
Spodnjo čeljust medvedov sestavljata dve spodnječeljustnični kosti (mandibuli).
Spredaj se stikata v posebni zrasti (simfizi), ki nikoli ne okosteni. Zgornjo čeljust na
32_Irena Debeljak
Ontogenetski razvoj zobovja pri medvedih (družina Ursidae)
Nekaj podatkov o izraščanju stalnih zob pri recentnih medvedih najdemo v
naslednjih delih: Pohle, 1923; Couturier, 1954; Rausch, 1961; Marks in
Erickson, 1966. Najbolj natančno pa je razvoj mlečnega zobovja in zamenjavo s
stalnimi zobmi pri rjavem medvedu raziskal Dittrich (1960). Ugotovil je, da je ta
proces enak in sočasen tudi pri drugih vrstah medvedov. Zaporedje izraščanja
posameznih zob iz dlesni je predstavljeno na sliki 1. Druge Dittrichove podatke o
ontogenetskem razvoju zobovja pri medvedih lahko strnemo v naslednje bistvene
ugotovitve:
Mladiči se skotijo brez zob. Prvi mlečni zobje začnejo izraščati v drugem mesecu
življenja in so v tretjem mesecu na svojem mestu. Prvi stalni kočniki začnejo prodirati
skozi diesen v petem mesecu življenja. Šele potem ko zraste prvi par stalnih molarjev
(М^&М^), lahko mladiči žvečijo trdo hrano. Mlečno zobovje pri tem nima skorajda
nobenega funkcionalnega pomena. Mlečni zobje izpadejo do konca 15. meseca. Zadnji
stalni zobje dokončno izrastejo pri povprečni starosti okoli enega leta in pol.
Dittrich (1960, 119-123) je ugotovil, da prehranjenost (telesna teža) pri medve-
dih navadno ne vpliva na razvoj in hitrost izraščanja zobovja. Tudi individualne raz-
like so pri tem procesu razmeroma majhne (glej si. 1).
Razporeditev mlečnih in stalnih zob v čeljustih mladiča rjavega medveda pona-
zarjata sliki 2a in 2b. —-----
vsaki strani oblikujeta dve parni kosti: medčeljustnica, ki nosi sekalce in sega do
podočnika ter zgornja čeljustnica ali maksila. Ti dve kosti sta koščeno zraščeni samo
pri odraslih medvedih. V čeljustnicah so oblikovane zobnice ali alveole, v katerih
tičijo zobne korenine.
Tako rjavi kot tudi jamski medved imata v obeh čeljustih na vsaki strani naslednje
mlečne zobe: po 3 sekalce ali incizive (dil-3), 1 podočnik ali kanin (dc) in ponavadi 3
ličnike ali premolarje (d2-4 oz. p2-4). Na vsaki strani spodnje čeljusti jamskega
medveda so naslednji stalni zobje: trije incizivi (I^.g), kanin (C), ponavadi samo en
premolar (Р^) in trije meljaki ali molarji (M^g). V zgornji čeljusti je en molar manj.
Kočniki imajo široko žvekalno površino z nizkimi, zaokroženimi grbinicami. Že
zgodnje raziskave morfologije zobovja in lobanje so pokazale, da so bili jamski
medvedi predvsem rastlinojedi (cf. Kurten, 1976). Sodobne izotopske analize so to
domnevo potrdile (Bocherens et al., 1994).
Stalno zobovje medvedov je podrobno opisal Rode (1935). Koby (1952) in Radu-
le s c u in S a m s o n (1959) pa so opisali mlečno zobovje jamskega medveda.
Pri orientaciji čeljustnic in zob so v rabi različni izrazi. V tem prispevku se
srečamo z naslednjimi: Spredaj - anteriorno - mezialno. Zadaj - posteriorno - distai-
ne. (Poenostavljeno! Vsi našteti izrazi sicer niso ekvivalentni.) Proti licu - bukalno -
lateralno. Proti jeziku - lingvalno (pri mandibuli) oziroma palatinalno (pri maksili).
Grizna (zgornja) površina zob je okluzalna.
Ontogenetski razvoj zobovja pri jamskem medvedu_33
Ontogenetski razvoj zobovja pri jamskem medvedu
Prvi trije meseci
Kostni ostanki še nerojenih živali (fetusov) in tistih mladičkov, ki so poginili ob
rojstvu ali kmalu zatem (neonati), so se v pleistocenskih najdiščih ohranili le izjemo-
ma. Tovrstne najdbe v Divjih babah pa kljub temu niti niso tako redke, saj je jama kot
brlog skoz dolga tisočletja služila predvsem samicam jamskega medveda, ki so tu v
zimskih mesecih, od decembra do februarja kotile mladiče (Turk et al., 1989b;
Debeljak, 1997). Drobne in zaradi poroznosti krhke spodnje čeljustnice še neroje-
nih ali novorojenih medvedkov so dolge 2-3 centimetre, široke pa le okoli 5 milime-
trov.
Mladiči jamskega medveda so se skotili brez zob. Tako je tudi pri današnjih
medvedih. Že v prvem tednu življenja pa najdemo v preparatih čeljusti rjavega
medveda zametke mlečnih zob: majhne, votle vršičke kron, ki še niso prodrli iz dlesni
(Dittrich, 1960, 11, si. 1, 2). To fazo ontogenetskega razvoja predstavlja naslednji
primer:
1. (Tab. 1, si. 1, 2) - Leva in desna mandíbula dveh neonatov, ki sta poginila že v
prvih dneh po rojstvu: Zaradi nazornosti sta mandibuli na sliki združeni v naravni
legi, čeprav ne izvirata od istega osebka. Od strani vidimo (tab. 1, si. 2), da je telo
mandibule polkrožno upognjeno, kar je značilno za neonate. Na polomljeni zgornji
površini se lepo vidita zametka obeh mlečnih kaninov in celo zametek protokonida
zadnjega mlečnega zoba d^ oz. p^, kot ga nekateri označujejo. (Protokonid je osrednja,
največja grbinica na omenjenem zobu). Zametki mlečnih zob so bili prvotno zaprti v
kosti. V tistem času so se alveole, skozi katere bi kasneje prodrli rastoči mlečni zobje,
šele oblikovale. Dolžina opisane mandibule je znašala okoli 4 centimetre; toliko, kot
pri novorojenih mladičih rjavega medveda.
Ehrenberg (1973) je dokumentiral najdbo skoraj popolnega skeleta neonata,
starega približno 10 dni iz avstrijskega nahajališča Salzofenhöhle. Po različnih izme-
rah in rekonstrukciji, ki so jo naredili iz kosti, je ugotovil, da so bili mladiči jamskega
medveda ob rojstvu morda le malenkostno večji kot pri rjavem medvedu. V leglu
rjavega medveda so običajno dva do trije kot podgane veliki mladiči, ki tehtajo le
350-400 gramov. So goli, slepi in popolnoma nemočni. Sami še ne morejo vzdrževati
svoje telesne temperature. Preživijo lahko le ob skrbni materi, v pred mrazom zavaro-
vanem okolju brloga.
Drugi in tretji mesec življenja so tudi mladiči jamskega medveda zagotovo
preživeli v brlogu oziroma jami. Samica jih ni zapuščala. V dolgih mesecih do nastopa
pomladi je živela le od maščobne zaloge, ki si jo je nabrala pozno poleti in jeseni. Za
njene mladiče je bil to čas dojenja; izključno mlečne prehrane. Medtem so vsi mlečni
zobje postopoma izrasli iz dlesni. Pod njimi, skrite v kosti, pa so se oblikovale in
krepile krone stalnih zob. Zaporedje izraščanja posameznih mlečnih zob lahko rekon-
struiramo s pomočjo podatkov za rjavega medveda (si. 1). To obdobje ontogenetskega
razvoja predstavljata naslednja dva primera:
2. (Tab. 2, si. 1-3) - Mandíbula mladiča, starega окоИ 2 do 2,5 meseca: Krona prve-
ga stalnega molarja М^ je že izoblikovana; na rentgenskem posnetku (tab. 2, si. 2, 3) se
lepo vidi kot tanka, votla lupina, ki je zaprta v čeljustnici. Rasti so začeli tudi prvi
milimetri stene korenine. V notranjosti mandibule tičita vršička oziroma zametka
kron P4 in C. Stalni zobje so se razvijali v votlih delih mandibule, med katerimi so
tanki prekati. Na zgornji strani čeljustnice, na mestu, kjer bi kasneje izrastel М^ zeva
34_Irena Debeljak
Četrti do šesti mesec življenja
V četrtem mesecu imajo medvedje že vse mlečne zobe. Bolj ali manj formirane
krone stalnih zob pa so medtem zaprte v čeljustnicah in se postopoma krepijo. Tako je
na primer pri štirimesečnem mladiču pod mlečnim zobom d^ že oblikovana krona
stalnega P4 (si. 2a, 2b). Z nadaljnjo rastjo korenine začne stalni zob izpodrivati
mlečnega. Močan protokonid krone P^ se pri tem zagozdi med oba kraka korenine d^
in sčasoma inducira kontaktno resorbcijo le-te. Podobno se zgodi tudi pri zgornjem
paru mlečnega d^ in stalnega P"*.
V petem mesecu začnejo pri medvedih izraščati prvi stalni kočniki (Ml). Najprej
pokuka iz dlesni sprednji del zoba М^ s protokonidom in parakonidom, kmalu zatem
pa še zadnji del krone z metakonidom in talonidom (Dittrich, 1960, 80-81). Na
pravkar opisani razvojni stopnji je zobovje mladiča rjavega medveda na sliki 2a.
Couturier (1954, 142-143) je objavil to rentgensko sliko ujetega mladiča in mu
prisodil starost treh mesecev. Po Dittrichovih (1960) podatkih pa je očitno, da je
bil mladič v resnici starejši; imel je vsaj 4 mesece.
Radulescu in Samson (1959, 211, si. 11) sta objavila fotografijo mandibule
približno 4-mesečnega jamskega medveda. Musil (1965, 72, tab. 3, si. 10) je pred-
stavil primerek mandibule, ki je morda nekoliko mlajši. Slike čeljustnice jamskega
medveda, ki bi bila tipična za petmesečnega mladiča (М^ ali М^ v fazi izraščanja) pa v
strokovni literaturi še nisem zasledila.
V osteološki zbirki iz najdišča Divje babe I nimamo nobene za objavo primerne
čeljustnice 4 do 5 mesecev starega mladiča. To pravzaprav ni naključje, saj tudi med
sicer izredno številnimi izoliranimi mlečnimi zobmi najdemo le redke primerke, ki bi
jih lahko uvrstili v to starostno skupino. (Takšni so na primer zgornji ali spodnji d4 z
okrepljeno korenino, ki je na konceh že nekoliko resorbirana. Posamezne konice na
ozka reža. Pred njo so luknjice; to so alveole, v katerih so tičale korenine mlečnih pre-
molarjev d^ in dg. Dokazujejo nam, da sta omenjena mlečna zoba že izrastla iz čelju-
stnice, torej mladič po vsej verjetnosti ni bil mlajši od dveh mesecev. Mandíbula je
bila približno tako dolga kot pri približno štiri mesece starem rjavem medvedu (si.
2a), vendar precej bolj robustna.
3. (Tab. 3, si. 1-3) - Obe polovici mandibule mladiča, starega okoli 2,5 do 3 mesece:
Brazda na mestu, kjer bi čez mesec ali dva začel izraščati М^, se je že razširila. Z
zgornje strani se skoznjo vidi temna, kot jajčna lupina krhka krona М^. Oblikovala se
je že zgornja četrtina korenine Mj (tab. 3, si. 2, 3), ki pa je tanka kot papir Tudi krone
stalnih incizivov in zametki C in P^ so zaprti v čeljustnici. Na zgornji strani mandi-
bule se lepo razločijo alveole mlečnih zob. Pri tej starosti so ravnokar izrastli skoraj-
da vsi mlečni zobje, vendar se tu niso ohranili. (Proces izraščanja mlečnih zob lahko
ponazorimo s primerom d4: Pri starosti 1 do 2 meseca je bila v čeljusti zaprta krona d^
temno rjave barve, motna in zelo krhka. Kasneje se je svetleje obarvala najprej konica
protokonida, to je konica, ki prva prodre skozi diesen, in potem postopoma še pre-
ostali del krone. Pri 2- do 3-mesečnih mladičih je bila krona izraščenega d^ že okre-
pljena, normalno svetla in sklenina je dobila značilen sijaj. Korenina pa je bila še
vedno votla, in zato precej krhka.)
Zgoraj opisana mandíbula je tako velika kot pri polletnem rjavem medvedu. Za
primerjavo nam lahko služi skica bistveno manjše mandibule trimesečnega recentne-
ga rjavega medveda, ki jo je objavil Pohle, 1923.
Ontogenetski razvoj zobovja pri jamskem medvedu__35
Sedmi in osmi mesec življenja
Mladiči so dočakali poletje. Za vso medvedjo družino je prišel čas intenzivnega
prehranjevanja. V naslednjih mesecih so morali pridobiti zadostno plast maščevja, če
so hoteli preživeti stradanje med naslednjo zimo. Zobje 6- do 8-mesečnih mladičev so
bili takrat v naslednjem stanju:
4. (Tab. 4, si. 1-5) - Mandíbula samice, stare okoli 6-7 mesecev: Razvoj je v primer-
javi s prejšnjim primerkom (tab. 3) precej napredoval. Krone vseh stalnih zob so že
oblikovane. Kasneje ne bi več rasile, ampak bi se le še okrepile, s tem da bi se notran-
jost postopoma zapolnila z zobovino oz. dentinom. М^ je bil pri tem mladiču že kak
mesec na "svojem mestu" v čeljusti in ima razvite več kot 4/5 korenine. Krona se je
nekoliko okrepila, korenina pa je še povsem votla in odprta na apeksih (tab. 4, si. 5).
Na Mj so očitni prvi znaki obrabe, kar kaže, da je medvedek že nekaj časa grizel trdo
hrano. Pri žvečenju so nastale številne drobne obrabne fasete z značilno svetlečo,
zglajeno površino. Na fotografijah in rentgenskem posnetku se lepo vidi, kako onto-
genetski razvoj pri posameznih zobeh različno napreduje; v skladu s podatki za rjave-
ga medveda, podanimi na si. 1. М^ v razvoju prehiteva druge stalne zobe. Sledi mu I^,
ki je bil v tem času že izraščen, vendar se ni ohranil. Ц je prodrl skoz diesen malo pre-
den je mladič poginil, P^ in Mg pa sta bila tik na tem. Vršička njunih kron sta se že
svetleje obarvala. Zadnji sekalec Ig je še vedno zaprt v mandibuli in ga vidimo le na
rentgenski sliki. Prav tako podočnik, ki ima oblikovano samo krono, korenine pa še
ne. P4 je v tem starostnem obdobju izpodrival mlečna zoba d4 in dg iz čeljusti. Njuna
korenina je bila takrat že močno resorbirana. Najkasneje čez kakšen mesec bi d^ (pri
našem primerku se ni ohranil) s popolnoma resorbirano korenino po naravni poti
izpadel iz dlesni. (Zadnji mlečni premolar d^ je pri medvedih v rabi zelo kratek čas;
pri žvečenju trdne hrane sodeluje le okoli 3 mesece, zato njegova žvekalna površina
praviloma nikoli ni močno obrušena.) Velikost zgoraj opisane mandibule ustreza leto
dni staremu mladiču rjavega medveda (tab. 9, si. 1; tab. 10, si. 2).
Ali so naše ocene starosti pravilne? Je bil razvoj zobovja pri jamskem medvedu
hitrejši, ali pa je morda zaostajal v primerjavi z rjavim medvedom? Razmislimo o tej
možnosti na primeru pravkar opisane čeljustnice:
Fiziološko nujno je, da je v šestem ali vsaj sedmem mesecu ontogenetski razvoj
tako napredoval, da je v denticijo že vključen prvi par stalnih molarjev. To velja za
današnje rjave medvede in prav nič drugače ni moglo biti pri jamskih medvedih. Kot
kroni so zaobljene in pogosto nosijo drobne obrabne fasete. Debeljak, 1996 a, 1997).
Očitno je bila smrtnost štiri- do petmesečnih mladičev v jami Divje babe precej nižja
kot v mlajših starostnih razredih.
Namen tokratnega prispevka ni razpravljati o možnih vzrokih različne stopnje
smrtnosti med letom. Omenim naj le, da je bil četrti do šesti mesec življenja čas
nastopa pomladi. Pri rjavem medvedu mladiči s samico zapustijo brlog po dopolnjen-
em tretjem mesecu; aprila ali maja, včasih šele v začetku junija. Verjetno je bilo tako
tudi pri jamskem medvedu.
Poleg mleka, ki ga sesajo pri materi, začnejo medvedje v petem ali šestem mesecu
gristi trdno hrano. To je mogoče šele takrat, ko zraste prvi par stalnih molarjev
(Dittrich, 1960, 14-15). Zgolj z majhnimi, koničastimi mlečnimi zobki si pri žveče-
nju ne bi mogli kaj prida pomagati. Šele z novimi kočniki pridobijo potrebno žvekal-
no površino.
36_Irena Debeljak
smo že omenili: pri začetnem prehodu na rastlinsko hrano največjo vlogo odigrajo
prav prvi stalni molarji Ml, kasneje pa so se jim pridružijo tudi nekateri drugi stalni
zobje (si. 1). Takrat materino mleko za rast postopoma ne zadostuje več in mladiči se
morajo začeti prehranjevati tudi s trdno hrano. Mlečni zobje z izjemo zadnjih
kočnikov d4 so tako majhni, da pri žvečenju trde rastlinske hrane nimajo praktično
nobenega funkcionalnega pomena (Dittrich, 1960, 14-15, 50, 81-82).
Starost opisane čeljustnice jamskega medveda torej ne more bistveno odstopati od
naše ocene. Če bi bila starost precej višja, М^ s svojo žvekalno površino ne bi bil do-
volj zgodaj "na mestu", da bi se rastoči mladič lahko primerno hranil in tako kar naj-
bolje izkoristil poletno in jesensko vegetacijsko obdobje oz. hrano, ki je bila takrat na
voljo. Proti nižji starosti pa pričata velikost mandibule in obraba М^, ki ni mogla na-
stati ob zgolj mlečni prehrani. To bi morda lahko dokazali tudi z izotopskimi anali-
zami zobnih tkiv.
Menim torej, da pri ocenah starosti niso nastale velike ali celo bistvene napake in
da je pri ontogenetskem razvoju zobovja jamskega medveda primerjava z rjavim
medvedom umestna.
5. (Tab. 5, si. 1, 2) - Mandíbula samca, starega okoli 6,5-7,5 mesecev: Velikost te
čeljustnice je že skoraj tolikšna kot pri poldrugo leto starem rjavem medvedu (tab. 16,
si. 1, 2; tab. 18, si. 1). Mg s sprednjim delom prodira iz mandibule. Sklenina pri tem
postopoma postaja vse svetlejša. Pri podočniku se je ravnokar pričela oblikovati
stena korenine. Krona Mg je zaprta v dvigajoči se spodnječeljustnični veji in je zato
značilno temno rjave barve, brez sijaja. Tanka koščena stena nad Mg je polomljena,
zato se lepo vidi, da je žvekalna površina obrnjena lingvalno (proti jeziku) in s spred-
njim delom usmerjena navpično navzdol. Šele z nadaljnjo rastjo čeljustnice bi nastal
prostor za zadnja dva molarja. (Mg se mora pri medvedih zavrteti za 90° v dveh
smereh, da se vključi v zobno vrsto.)
6. (Tab. 6, si. 1-4) - Mandíbula samice, stare okoli 6,5-7,5 mesecev: Ta čeljustnica
je pripadala mladiču podobne starosti kot v prejšnjem primeru, morda je le za malen-
kost starejša. М^ je bil že nekaj časa "na mestu" in v rabi, zato njegova krona nosi
približno 3 milimetre velike plitve obrabne fasete. Stena korenine je skoraj v celoti
oblikovana, vendar na konceh še vedno odprta (tab. 6, si. 4). Več kot pol krone Mg že
gleda iz mandibule; oblikovala se je približno polovica korenine. Njena stena je zelo
tanka, notranjost pa votla (tab. 6, si. 4). Korenina М^ je bolj razvita in trdna; stena je
debela približno 1 milimeter V isti etapi ontogenetskega razvoja oziroma pri isti sta-
rosti zadnji spodnji molar Mg sploh še nima korenine, tanka ploska krona tega zoba
pa se zlahka razlomi (tab. 5).
Zelo očitno je, da so bili posamezni zobje istega mladiča različno razviti, različno
mehansko odporni, in zato niso imeli enakih možnosti, da se fosilno ohranijo. Pri
analizah izoliranih zob moramo računati z različnimi tafonomskimi izgubami. Do teh
razlik je prišlo tako zaradi specifične oblike in velikosti posameznih zob kot tudi
zaradi različne razvitosti oziroma trdnosti pri določeni starosti.
Zanimivo je primerjati velikosti mandibul na tablah 4-6 (in tudi 11-15). Normalno
je, da je velikost kosti odvisna od starosti osebka. Opazimo pa, da je velikost čeljust-
nic tudi pri podobni starosti lahko precej različna, sorazmerno z velikostjo stalnih
zob. Ti praktično v celoti zapolnjujejo čeljustnice, kar se lepo vidi na rentgenskih
posnetkih. Večji zobje zahtevajo tudi več prostora. Ugotovimo lahko:
1. Jamski medved je imel izrazito večje zobe kakor današnji rjavi medved. Razu-
mljivo je, da so morale biti njegove čeljusti pri isti ontogenetski stopnji in starosti
precej večje in bolj robustne. Čeprav so bili mladiči jamskega medveda ob rojstvu
Ontogenetski razvoj zobovja pri jamskem medvedu_37
komajda kaj večji kakor pri rjavem medvedu, je bila rast njihovih čeljusti v nasled-
njih mesecih bistveno hitrejša. Tako smo na primer ugotovili, da mandíbula dobre pol
leta starega jamskega medveda (tab. 5) lahko meri toliko kot pri poldrugo leto starem
rjavem medvedu. Ali je bilo toliko večje tudi preostalo telo? S tako hitrim narašča-
njem telesne mase pri mladičih jamskega medveda skorajda ne moremo računati.
Samica bi težko vzredila dva ali celo tri tako velike mladiče že v prvem polletju, ko je
bila prehrana pretežno mlečna. Bolj verjetno je, da so imeli mladiči izrazito velike če-
ljusti oz. gobec. Razmerje čeljusti/telo bi torej moralo biti bistveno večje kot pri odra-
slih jamskih medvedih in večje kot pri mladičih rjavega medveda. Pri edinem natan-
čno opisanem in izmerjenem skeletu približno sedemmesečnega mladiča jamskega
medveda (tovrstne najdbe so namreč izjemno redke!) najdemo potrditev te domneve.
Avtor tega članka Ehrenberg (1964, 243-244) je bil presenečen nad odkritjem, da je
obrazni del lobanje izrazito večji, kakor bi bilo pričakovati glede na možganski del
lobanje, kratek trup in šibek toraks. Rekonstrukcija je pokazala, da je pri skupni
dolžini 60cm in višini 30cm več kot eno tretjino zavzemala glava (Ehrenberg,
1964, 223). Menim, da takšnemu "nesorazmerju" botruje prav funkcionalni razvoj
zobovja, ki je moral biti tako hiter kot pri današnjem rjavem medvedu. Čeljust pa se
je pri tem ustrezno prilagodila rastočim zobem.
2. Samci jamskega medveda imajo v povprečju večje zobe kakor samice. Predvsem
velja to za kanine, po katerih lahko glede na velikost določamo spol (Koby, 1949;
Kurten, 1955). Široka baza krone kanina in njegova rastoča korenina zasedata pri
mladičih zelo velik del čeljustnic. Na rentgenskih posnetkih se lepo vidi, da sta višina
in debelina telesa mandibule pri določeni starosti odvisni prav od velikosti kanina.
Številni primerki iz Divjih bab kažejo, da so bile na isti razvojni (ontogenetski) stop-
nji mandibule samic manjše in bolj gracilne kakor pri samcih. Po tem bi lahko
sklepali, da je bil spolni dimorfizem na čeljustnicah jamskega medveda izražen že v
prvem letu življenja. Pomisliti pa moramo še na eno možnost: da je razvoj stalnega
zobovja pri samcih zaostajal v primerjavi s samicami. Vendar, če so takšne razlike v
razvoju sploh obstajale, niso mogle biti bistvene zaradi že večkrat omenjenega razlo-
ga: Mladiču so pri določeni starosti morali izrasti prvi stalni zobje, da se je lahko
ustrezno prehranjeval. Tudi pri danes živečih medvedih v procesu izraščanja zob niso
ugotovili pomembnih razlik med spoloma (Dittrich, 1960; Marks & Erickson,
1966, 393).
Vsaj na enem primerku si oglejmo še stanje v zgornji čeljusti:
7. (Tab. 7, si. 1-3) - Medčeljustnica in maksila samca, starega okoli 6,5-7,5 mese-
cev: Obe kosti pri tej starosti nista neločljivo spojeni. Pri današnjih medvedih se
dokončno zrasteta šele pri odraslih živalih, po 4. letu (Marks & Erickson, 1966,
398-400). Na kroni М^ najdemo prve znake obrabe. Po obliki alveole sodeč, je bil P"^
ravno v fazi izraščanja; večina njegove krone je zagotovo že prodrla iz čeljustnice. Od
sekalcev se je ohranil le I^, ki je malo pred poginom tega mladiča z vršičkom krone
morda že prodrl skozi diesen. Ležišče korenine je nepoškodovano, tako da lahko
ugotovimo, da je bil zob že dokončno izraščen. Nasprotno pa ozka odprtina alveole
dokazuje, da se izraščanje tega inciziva sploh še ni začelo. Nad pravkar omenjeno
alveolo je ohranjena tudi plitva alveola mlečnega di^, ki je pri tej starosti že tičal v če-
ljusti, čez kak mesec pa bi po naravni poti izpadel iz dlesni. Zgornji podočnik je skrit
v maksili. Na rentgenskem posnetku (tab. 7, si. 3) vidimo, da se njegova korenina še ni
začela formirati. Krona je votla in še precej pod, ali bolje rečeno nad robom zgornje
čeljustnice. Globoko ležišče korenine mlečnega podočnika je v celoti ohranjeno in s
trdno koščeno steno popolnoma ločeno od razvijajoče krone stalnega kanina, zato
38__Irena Debeljak
Od devetega meseca do dopolnjenega prvega leta
V 9. ali 10. mesecu življenja pri medvedih dokončno izrastejo drugi spodnji molar-
ji Mg. Zadnji zgornji molarji М^ začnejo izraščati v devetem mesecu. Po desetem me-
secu že lahko začnejo prodirati skozi čeljustnico stalni kanini. Malo pred dopolnjenim
prvim letom (11. ali 12. mesec) pa predrejo diesen tudi zadnji spodnji molarji Mg. Za-
radi poševne lege in izrazito ploske krone mine še precej časa, preden v celoti izraste-
jo.
Ehrenberg (1931, tab. 120, si. 6) je objavil fotografijo mandibule mladiča jam-
skega medveda, ki bi mu lahko pripisali starost približno 8-9 mesecev.
Na tabli 8, si. 1 in tabli 10, si. 1 je spodnja čeljustnica recentnega, okoli 10 mesecev
starega rjavega medveda iz Slovenije. Sprednji del Mg je "zunaj". Vršički stalnih ka-
sklepamo, da korenina mlečnega kanina na tej stopnji ontogenetskega razvoja še ni
bila prizadeta zaradi kontaktne resorbcije.
Preden končamo z opisom ontogenetskega razvoja zobovja v sedmem in osmem
mesecu življenja, naj omenim še eno zanimivost: Med juvenilnimi čeljustnicami iz
Divjih bab I imamo največ primerkov ravno iz pravkar obravnavanega starostnega
obdobja, čeprav bi po ugotovitvah drugih raziskovalcev (Ehrenberg, 1931, 1964;
Kurten, 1958, 1976) ostanki 7-mesečnih mladičev, ki so poginili sredi poletja, morali
biti prava redkost. Splošno uveljavljeno prepričanje, ki je obveljalo v zadnjih deset-
letjih, je, da množični ostanki jamskega medveda v jamah izvirajo od živali, ki so po-
ginile zaradi izčrpanosti med dolgo hibernacijo, pozimi in predvsem tik pred nasto-
pom pomladi. Vendar, tudi analiza izoliranih zob d4 in М^ je pokazala, da izredno ve-
lik delež v fosilni populaciji zavzemajo prav mladiči, ki so poginili pri domnevni sta-
rosti 6-8 mesecev, od julija do septembra (Debeljak, 1996a, 1997). Divje babe I kot
tipično najdišče jamskega medveda gotovo ne predstavljajo nobene izjeme, zato so
takšni rezultati o sestavi fosilne populacije presenetljivi in nepričakovani. Razložimo
jih lahko na dva različna načina:
a) Naše ocene individualne starosti (in s tem tudi izoliranih juvenilnih zob) niso
pravilne, in tako najpogostejša starostna skupina domnevno 7-mesečnih živali dejan-
sko predstavlja tiste mladiče, ki so poginili med drugo hibernacijo. V tem primeru bi
moral ontogenetski razvoj zobovja jamskega medveda kar za 6 mesecev zaostajati za
ontogenetskim razvojem, ki so ga ugotovili pri današnjih medvedih. Glede na že ome-
njene prehranjevalne navade in potrebe v prvem letu se to zdi skoraj nemogoče. Po
drugi strani pa bi lahko v podporo zgornji domnevi navedli videz prve tanke cemen-
tne obloge na korenini М^. To cementno plast sicer razlagamo kot "neonatno linijo"
(Debeljak, 1996a, 29-30, tab. 26-28), vendar je precej podobna "zimskim" prira-
stnicam.
b) Druga možna interpretacija očitnega razhajanja med pričakovanim in ugotov-
ljenim mortalitetnim profilom: Ocene starosti so pravilne. Življenjske navade in smrt-
nost famskega medveda so potemtakem bistveno drugačne, kot smo domnevali do
zdaj. (Podobno je že Musil (1965, 74-76) na podlagi merjenja dolgih kosti okončin
prišel do sklepa, da so jamski medvedi zahajali v jamo Pod hradem in tam umirali
tudi v poletnih mesecih.)
Dokončen odgovor na zastavljena vprašanja bodo morda omogočile nadaljnje
raziskave ontogenetskega razvoja pri današnjih, v različnih okoljih živečih medvedih,
pa tudi natančne analize zobnega cementa pri mladičih.
Ontogenetski razvoj zobovja pri jamskem medvedu__39
Od enega leta do poldrugega leta
V času od enega leta do poldrugega leta se pri medvedih končuje proces izraščanja
stalnega zobovja. Individualne razlike pri tem postajajo vse bolj izrazite (Dittrich,
1960), zato starosti ne moremo določiti tako natančno kot prej. Zadnji stalni zobje
(М^, Mg in kanini) so pri poldrugo leto starih recentnih medvedih praviloma dokon-
čno izraščeni. To obdobje ontogenetskega razvoja pri jamskem medvedu nam pred-
stavljajo naslednji trije primerki. Njihovo individualno starost sem ocenila na podlagi
podatkov za današnje rjave medvede. Morali pa bi upoštevati tudi možnost, da je bil
ontogenetski razvoj zobovja pri jamskem medvedu počasnejši. V tem primeru bi
lahko naslednje tri mandibule pripadale dveletnim ali celo nekoliko starejšim
mladičem, ki so poginili v svoji tretji zimi.
8. (Tab. 11, si. 1, 2; tab. 13, si. 1) - Mandíbula samca, starega 12-15 mesecev: Veli-
kost te mandibule je bila tolikšna kot pri odraslem recentnem rjavem medvedu. Sim-
fizni del, kjer sta bili leva in desna mandíbula povezani, je najbrž patološko spreme-
njen. Vnetna sprememba je morda nastala ob kakšni travmatski poškodbi čeljusti.
Kanin je že precej razvit. Dober centimeter in pol krone gleda iz alveole in oblikovana
je že več kot polovica stene korenine. Sprednja polovica žvekalne površine Mg je rahlo
obrabljena. Velik del krone Mg še ni prodrl skozi diesen. Njegova lega je glede na pre-
ostale zobe še vedno poševna.
Pri izraščanju zadnjega kočnika Mg se je včasih zgodilo, da se je njegova krona za-
gozdila ob krono sosednega Mg. Na nekaterih mandibulah jamskega medveda lahko
opazimo s tem povezane patološke spremembe, ki so živalim prav gotovo povzročale
hude težave. Po nekaterih avtorjih so bile nepravilnosti pri izraščanju zadnji kočni-
kov glavni ali pa vsaj zelo velik vzrok smrtnosti pri mladičih v drugi zimi (Ehren-
berg, 1931; Abel, 1931.) Z raziskavami v Divjih babah tega nismo mogli potrditi.
Menim, da bi omenjene težave jamske medvede resno ogrožale kvečjemu kasneje v
življenju. Čeprav je seveda mogoče, da se je morebitna okužba pri oslabelem enolet-
nem mladiču lahko končala tudi s smrtnim izidom.
9. (Tab. 12, si. 1, 2; tab. 13, si. 2) - Mandíbula samice, stare okoli 15 mesecev:
Oblikovani sta že dve tretjini korenine podočnika. Krona še ni v celoti izrastla; za
ninov so ravnokar pogledali iz alveole, vendar skozi diesen še niso prodrli. Latero-
distalno od njih so mlečni kanini. Vsi drugi mlečni zobje so do te starosti že izpadli.
Mandíbula na tabli 9, si. 1 in tabli 10, si. 2 je pripadala okoli eno leto staremu ko-
čevskemu rjavemu medvedu. Nekaj več kot 1 cm kanina sega čez rob alveole. Ob njem
še vedno tiči mlečni kanin z obrabljeno krono in močno resorbirano korenino. V času
zamenjave podočnikov imajo medvedje kar nekaj časa v dlesnih stalne in mlečne
kanine hkrati. Mlečni kanini izpadejo šele pri starosti 12-15 mesecev, med zimova-
njem v brlogu.
Zgornja primera mandibul rjavega medveda predstavljamo zato, ker za obravna-
vano starostno obdobje v zbirki iz Divjih bab nimamo nobene primerne čeljustnice.
Tudi pri izoliranih zobeh smo opazili zelo izrazito vrzel, ki kaže, da v Divjih babah
skorajda ni ostankov jamskih medvedov, ki bi poginili med 10. mesecem in dopolnje-
nim prvim letom življenja, to je v prvi polovici zimovanja v brlogu (Debeljak,
1996 a, 1997).
Vendar, glede na zgornjo razpravo je možno tudi to, da manjkajoča starostna sku-
pina predstavlja mladiče iz naslednjega poletja.
40_Irena Debeljak
Nadaljnji razvoj zob in čeljusti
Domnevno na polovici ali proti koncu drugega leta življenja so imeli jamski me-
dvedi že izraščeno cfelotno stalno zobovje. Zobje pa so se kljub temu razvijali še na-
prej. Prvotno votle korenine in krone so se vse bolj zapolnjevale z zobovino ali dentin-
om. Končno je v sredini ostal samo še ozek kanal in pulpna votlina na prehodu iz
korenine v krono. Predvidevamo, da so se pri jamskem medvedu okoli 4. leta zaprle še
zadnje zobne korenine: М^, Mg in kaninov. V začetku eksplozivna rast čeljusti se je v
naslednjih letih vse bolj umirjala.
dobra dva centimetra sega čez rob alveole. Mg še ni čisto "na mestu"oz. v okluzalni
ravnini. Korenina in Mg je na konceh še vedno odprta. М^ ima zaprto korenino in
"oglajeno" krono s posameznimi, 2-3 mm širokimi obrabnimi fasetami. Tudi na
sprednjem delu Mg je obraba že očitna. Na žvekalni površini Mg še ni sledov obrabe.
Zaradi gneče v zobni vrsti posamezni zobje pritiskajo eden na drugega. (Po prvem
letu so se ob stiku nekaterih zob začele nakazovati značilne fasete ter se sčasoma še
povečale in poglobile. Še posebej je to izrazito na anteriorni steni krone Mg in posteri-
orni steni krone М^. Takšen tip obrabe imenujemo aproksimalna obraba; za razliko
od okluzalne obrabe na žvekalni površini.)
Za primerjavo lahko vzamemo spodnjo čeljustnico slabo leto in pol starega rjave-
ga medveda iz okolice Kočevja (tab. 16, si. 1, 2.; tab. 18, si. 1): Tudi pri njem kanini še
niso docela izrastli. Korenine zob pa so z izjemo Mg in kanina že zaprte. Krona Mg še
ni v celoti pogledala iz dlesni. Na podobni ontogenetski stopnji je naslednji primerek:
10. (Tab. 14, si. 1, 2; tab. 15, si. 1-3) - Mandíbula samice jamskega medveda, stare
okoli eno leto in pol: Kanin je nekoliko bolj razvit kakor pri ravnokar omenjenem
rjavem medvedu. Krona je praktično v celoti izrastla, manjka samo še kakšen centime-
ter korenine. Mg je že na svojem mestu v zobni vrsti. М^ je še nekoliko bolj obrabljen
kakor pri prejšnjih primerkih. Površina je zglajena in posuta z majhnimi obrabnimi
fasetami. Ob stiku М^ in Mg je na obeh zobeh nastala izrazita faseta (aproksimalna
obraba). Na posteriorni steni krone М^ je ta faseta široka kar 4 mm. Korenina М^ se je
zaprla že v prvem letu. Pri starosti okoli poldrugega leta je njena stena debela pri-
bližno 2,5-2,75 milimetra. Pri Mg sta konici korenine le še nekoliko perforirani.
Korenina Mg pa še vedno široko zeva in ima zelo krhko steno (tab. 15, si. 3).
Izolirane zobe ponavadi opredelijo kot juvenilne, če je korenina odprta, oziroma
aduline, ko je korenina zaprta. Pri tem so nekateri zobje istega osebka označeni kot
adultni, drugi, ki v razvoju zaostajajo, pa kot juvenilni. Problem pa ni samo v dvolič-
nosti podatkov. Omenjena klasifikacija ni ustrezna predvsem zato, ker se na ta način
velik delež zob mladičev napačno prišteje med odrasle (na to je bilo opozorjeno tudi v:
Turk et al., 1992). Medved odraste šele okoli 4. leta. Korenina М^ se zapre že pred
dopolnjenim prvim letom starosti. Mg in P^ pa pri poldrugem letu. Zaprtost korenine je
lahko kvečjemu kriterij za ugotavljanje odraslosti po zadnjih molarjih in kaninih.
Kot soavtorica sem dolžna opozoriti na napako v članku izpred petih let (Turk
et al., 1992), ko ontogenetskega razvoja zobovja pri medvedu še nismo dovolj dobro
poznali. V omenjenemu prispevku so bile statistično obdelane mere "adultnih"
molarjev М^, z namenom, da bi preučili razmerje obeh spolov med odraslimi jamski-
mi medvedi. V resnici gre za zobe, ki bi jih morali pripisati starejšim mladičem
(dveletniki, triletniki, morda še štiriletniki). Njihova korenina je bila zaprta, in na
podlagi tega kriterija smo jih napačno prišteli med odrasle.
Ontogenetski razvoj zobovja pri jamskem medvedu_41
Sklep
V prispevku je bil predstavljen ontogenetski razvoj zobovja pri jamskem medvedu
oziroma pri medvedih nasploh. Proces zamenjave mlečnega zobovja in izraščanja
stalnih zob se večinoma konča do poldrugega leta življenja. Do takrat so posamezne
ontogenetske faze dober indikator individualne starosti.
S pomočjo opisanih primerov in zbranih podatkov bomo lahko ocenili starost ju-
venilnih čeljustnic jamskega medveda in za silo tudi izoliranih juvenilnih zob. V bo-
doče bo treba natančno predstaviti tudi ontogenetski razvoj in kriterije za določanje
individualne starosti pri posameznih (izoliranih) zobeh, ki so najpogosteje ohranjeni
in najbolj informativni fosilni ostanki jamskega medveda.
V sklepu naj še enkrat povzamem glavne ugotovitve:
- Proces rasti zob in zamenjave mlečnega zobovja s stalnim je pri jamskem medve-
du potekal na enak način, prek enakih in verjetno tudi sinhronih razvojnih faz kot pri
sorodnih, danes živečih medvedih.
- Sklepamo lahko, da določena ontogenetska stopnja razvitosti zobovja jamskega
medveda ustreza približno isti starosti osebka kot pri rjavem medvedu. Razvoj zobov-
ja pri jamskem medvedu ni smel bistveno zaostajati, saj so mladiči pri določeni
starosti (6. ali vsaj 7. mesec življenja) potrebovali prvi par stalnih molarjev (М^&М^),
da so lahko pričeli žvečiti trdno rastlinsko hrano.
- Ta argument govori proti drugi možnosti, da je bil ontogenetski razvoj zobovja
pri jamskem medvedu dejansko precej počasnejši kot pri današnjih medvedih. Takšna
posebnost bi (v določenih okoliščinah) lahko ogrozila obstoj vrste. Omenjene domne-
ve pa zaenkrat vendarle ne moremo in ne smemo povsem ovreči.
- Velikost čeljustnic je bila v prvem letu življenja (pa tudi kasneje) odvisna od veli-
kosti stalnih zob, ki so se v temu času v njej razvijali in jo skoraj v celoti zapolnjevali.
- Rast čeljusti je bila pri mladičih jamskega medveda bistveno hitrejša kakor pri
današnjem rjavem medvedu. Že pri enem letu je bila njihova mandíbula tako velika
kot pri odraslem rjavem medvedu. To seveda ne pomeni, da je bilo toliko večje tudi
preostalo telo.
11. (Tab. 17, si. 1,2; tab. 18, si. 2) - Mandíbula subadultnega samca, starega okoli 4
leta: Starost tega primerka je bila določena s štetjem prirastnic na zobnem cementu.
Ta metoda velja za najbolj objektivno in se vsesplošno uporablja za ocenjevanje indi-
vidualne starosti pri divjih živalih (več v: Debeljak, 1996a, b). Zgoraj omenjeni
proces odlaganja dentina v notranjosti zob je že precej napredoval, kar se lepo vidi na
rentgenskem posnetku (tab. 18, si. 2). Krona М^ je najbolj obrabljena (predvsem pro-
tokonid in hipokonid). Mg manj in M3 zelo malo (tab. 17, si. 2). Ob stiku posameznih
molarjev so nastale precej globoke fasete. Na posteriorni steni krone М^ je takšna
faseta široka že več kot 6 mm. Dolžine krone tako ne bi bilo več mogoče res natančno
izmeriti. Po rentgenski sliki sodeč, se korenini kanina in Mg še nista docela zaprli,
vendar ne manjka dosti. Pri recentnih medvedih se korenina kanina zapre okoli 4.
leta (Marks & Erickson, 1966, 395, 397), to je v času, ko dosežejo spolno zrelost.
Pravkar opisana mandíbula še ni dosegla svoje končne velikosti. Mandibule dora-
slih samcev merijo v dolžino 5-10 centimetrov več. Rast čeljusti je torej napredovala
tudi po četrtem letu. Pri recentnem črnem medvedu glava samcev raste prvih 8 let, pri
samicah pa se ta rast ustavi nekoliko prej, kmalu po spolni zrelosti (Marks &
Erickson, 1966, 400-402). Najbrž je bilo podobno tudi pri jamskih medvedih.
42_Irena Debeljak
Zahvala
Ivanu Turku, vodji izkopavanj v Divjih babah I, se zahvaljujem za material, ki mi
ga je prepustil v obdelavo. Izkopavanja izvaja Inštitut za arheologijo Znanstvenorazi-
skovalnega centra SAZU. Na Kliniki za kirurgijo in male živali Veterinarske fakul-
tete v Ljubljani so prijazno omogočili rentgensko slikanje čeljustnic jamskega in
rjavega medveda, ki je lepo uspelo po strokovni zaslugi veterinarjev Teodore Ivanuša,
Janeza Štublja in Gregorja Freliha. Andrej Bidovec (Veterinarska fakulteta, Ljublja-
na) in Ciril Štrumbelj (Gojitveno lovišče Medved, Kočevje) sta posredovala za primer-
javo potrebne lobanje mladičev recentnega rjavega medveda iz Slovenije. Vida Pohar
je pregledala manuskript. Iskreno se zahvaljujem tudi vsem drugim, ki so kakorkoli
pomagali pri nastanku tega prispevka.
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7-9, 719-744, Wien.
Bocherens, H., Fi z et, M. & M ari otti. A., 1994: Diet, physiology and ecology of fossil
mammals as inferred from stable carbon and nitrogen isotope biogeochemistry: implications for
Pleistocene bears. - Paleogeogr Paleoclim. Palaeoecol. 107, 213-225, Amsterdam.
Couturier, M. A. J., 1954: L'ours brun {Ursus arctos L.). - 904 pp., Grenoble.
Debeljak, I., 1996a: Starostna sestava populacije jamskega medveda iz Divjih bab. (Age
structure of cave bear population from the Divje babe Cave.) - Magistrska naloga. Manuscript,
70 pp., 36 tab. Naravoslovnotehniška fakulteta. Oddelek za geologijo, Ljubljana.
D e b e 1 j a k. L, 1996b: A simple preparation technique of cave bear teeth for age determina-
tion by cementum increments. - Rev. Paléobiol. 15/1, 105-108, Genève.
Debeljak, L, 1997: Age composition of the cave bear population from the Divje babe I
Cave. - Int. Meeting on Man and Bear, Auberives-Pont en Royans (Vercors - Isère). (In press.)
D i 11 r i c h, L., 1960: Milchgebißentwicklung und Zahnwechsel beim Braunbären {Ursus arc-
tos L.) und anderen Ursiden. - Morph. Jb. 101/1, 1-141, Leipzig.
- Domnevamo, da je bil pri jamskih medvedih sekundarni spolni dimorfizem izra-
žen že v prvem letu življenja; samci so imeli večje čeljusti od samic.
- Splošno uveljavljena metoda ločevanja zob na juvenilne, z odprto korenino in
adultne, če je korenina zaprta, za večino zob pri jamskem medvedu ni ustrezna.
Medved odraste okoli 4. leta. Korenina М^ pa se na primer zapre že v prvem letu živl-
jenja (po 8. mesecu), večina drugih stalnih zob do poldrugega leta in samo korenine
М^, Mg in kaninov šele pri priblišno štirih letih.
- Pri študiju juvenilnih čeljustnic iz paleolitskega najdišča Divje babe I nismo mo-
gli spregledati dejstva, da je večina primerkov nekoč verjetno pripadala približno
sedemmesečnim mladičem, ki so torej poginili sredi poletja. To je v nasprotju z dose-
danjim mnenjem, da množični ostanki v tipičnih nahajališčih jamskega medveda iz-
virajo od živali, ki so zaradi izčrpanosti poginile med hibernacijo, pred nastopom po-
mladi.
- Zanimiv problem in naloga v prihodnosti bo: z nadaljnjimi raziskavami in do-
datnimi podatki dokazati to trditev in jo smiselno obrazložiti.
Ontogenetic development of dentition in the cave bear_ 43
Ehrenberg, K., 1931: Über die ontogenetische Entwicklung des Höhlenbären. In: O. Abel
& G. Kyrie (eds.). Die Drachenhöhle bei Mixnitz. - Speläolog. Monogr 7-9, 624-710, Wien.
Ehrenberg, K., 1964: Ein Jungbärenskelett und andere Höhlenbärenreste aus der Bären-
höhle im Hartlesgraben bei Hieflau (Steiermark). - Ann. Naturhistor Mus. Wien 67, 189-252,
Wien.
Ehrenberg, K., 1973: Ein fast vollständiges Höhlenbärenneonatenskelett aus der Salz-
ofenhöhle im Toten Gebirge. - Ann. Naturhistor Mus. Wien 77, 69-113, Wien.
Koby, F.-Ed., 1949: Le dimorphisme sexuel des canines d'Ursus arctos et d'U. spelaeus. -
Rev Suisse Zool. 56, 675-687, Genève.
Koby, F.-Ed., 1952: La dentition lactéale d'Ursus spelaeus. - Rev. Suisse Zool. 59, 511-541,
Genève.
Krystufek, B., 1991: Sesalci Slovenije. - Prirodoslovni muzej Slovenije, 294 pp., Ljub-
ljana.
Kurten, B., 1955: Sex dimorphism and size trends in the cave bear, Ursus spelaeus Rosen-
müller & Heinroth. - Acta Zool. Fennica 90, 1-48, Helsinki.
Kurten, B., 1958: Life and death of the Pleistocene cave bear A study in paleoecology. -
Acta Zool. Fennica 95, 1-59, Helsinki.
Kurten, B., 1976: The cave bear story. Life and death of a vanished animal. - Columbia
Univ. Press, 163 pp.. New York.
Macdonald, D. (ed.), 1985: The Encyclopedia of Mammals. Vol. 1. - Equinox (Oxford)
Ltd., London.
Macdonald, D. (ed.), 1996: Velika enciklopedija. Sesalci. - Založba Mladinska knjiga, 980
pp., Ljubljana.
Marks, S. A. & Erickson, A. W, 1966: Age determination in the black bear - J. Wildl.
Manage. 30/2, 389-410, Washington.
M u s i 1, R., 1965: Die Bärenhöhle Pod hradem. Die Entwicklung der Höhlenbären im letzten
Glazial. - Anthropos 18, 7-92, Brno.
Nelson, D. E. & Ku, T.-L., 1997: Radiokarbonsko datiranje kosti in oglja iz Divjih bab I.
Radiocarbon dating of bone and charcoal from Divje babe I cave. In: I. Turk (ed.). - Opera
Instituti Archaeologici Sloveniae 2, 51-65, Založba ZRC, Ljubljana.
Pohle, H., 1923: Über den Zahnwechsel der Bären. - Zool. Anz. 55, 266-277, Leipzig.
Rädulescu, C. & Samson, P, 1959: Contribution à la Connaissance de la Dentition lac-
téale d'Ursus spelaeus. - Eiszeitalter u. Gegenwart 10, 205-216, Öhringen.
Rausch, R. L., 1961: Notes on the black bear {Ursus americanus Pallas) in Alaska, with
particular reference to dentition and growth. - Z. Säugetierk. 26/2, 77-107, Berlin.
Rode, K., 1935: Untersuchungen über das Gebiß der Bären. - Monogr Geol. Palaeont. Ser
II, H. 7, 162 pp., Leipzig.
Turk, I. (ed.), 1997: Moustérienska "koščena piščal" in druge najdbe iz Divjih bab I v
Sloveniji. Mousterian "bone flute" and other finds from Divje babe I cave site in Slovenia. -
Opera Instituti Archaeologici Sloveniae 2, 223 pp, Založba ZRC, Ljubljana.
Turk, L, Dir j e C, J., S trm ole, D., Kranj C, A. & Čar, J., 1989 a: Stratigrafija Divjih bab
I. Izsledki izkopavanj 1980-1986. (Stratigraphy of Divje babe I. Results of excavations
1980-1986.) -Razpr IV. razr SAZU 30, 161-207, Ljubljana.
Turk, L, Dirjec, J. & Culiberg, M., 1989b: Divje babe I - novo paleolitsko najdišče in
skupinsko grobišče jamskega medveda. Poskus tafonomske analize na podlagi vzorcev iz dveh
sedimentnih in arheoloških kompleksov. (Divje babe I - a new palaeolithic site and a common
grave of the cave bear An attempt at a taphonomic analysis based on samples from a pair of
sedimentary and cultural units.) - Arh. vest. 39-40, 13-60, Ljubljana.
Turk, I., Dir j ec, J., Debelj ak, I. & Huber, Đ., 1992: Divje babe I-poskus uporabe sta-
tistične analize množičnih živalskih ostankov v paleolitski arheologiji. IV. Posamično najdeni
zobje jamskega medveda. (Divje babe I - an attempt to apply statistical analysis to the mass ani-
mal remains in the palaeolithic archaeology. IV. Isolated teeth of cave bear) - Arh. vest. 43, 7-22,
Ljubljana.
44
Irena Debeljak
Plate 1 - Tabla 1
Cave bear; left and right mandible of two neonates (from Quad. 86, spit XV, and Quad. 24, spit
XVII). Divje babe I
1 From above. Natural size (left) and magnification two times (right)
a = germ of deciduous canine, b = germ of deciduous premolar d^
2 Buccal side of right mandible. Natural size (left) and magnification two times (right)
Jamski medved; leva in desna mandíbula dveh neonatov (iz Kv. 86, izkop XV in Kv. 24, izkop
XVII). Divje babe I
1 Od zgoraj. Naravna velikost (levo) in dvakrat povečano (desno)
a = zametek mlečnega kanina, b = zametek mlečnega premolarja d^
2 Bukalna stran desne mandibule. Naravna velikost (levo) in dvakrat povečano (desno)
Ontogenetic development of dentition in the cave bear
45
Plate 2 - Tabla 2
Cave bear; left mandible (invt. num. 1357) of a cub approx. 2-2.5 months old. Divje babe I.
Natural size
1 From above
a = alveolus for dg, b = alveolus for d^, c = fissure above Mj
2 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri-
nary Faculty in Ljubljana)
3 Schematic illustration of germs of permanent teeth
Jamski medved; leva mandíbula (inv. št. 1357) mladiča, starega okoli 2-2,5 meseca. Divje babe I.
Naravna velikost
1 Od zgoraj
a = alveola za dg, b = alveola za d^, c = reža nad M,
2 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske
fakultete v Ljubljani)
3 Shematska ponazoritev zametkov stalnih zob
46__Irena Debeljak
Plate 3
Cave bear; left and right mandible (invt. num. 1375 and 1380) of a cub 2.5-3 months old. Divje
babe I. Natural size
1 From above
a = alveolae for di^_^, b = alveolus for dc, c = alveolus for dg, d = alveolus for d^, e = Mj^
2 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri-
nary Faculty in Ljubljana)
3 Schematic illustration of germs of permanent teeth
Tabla 3
Jamski medved; leva in desna mandíbula (inv. št. 1375 in 1380) mladiča, starega okoli 2,5-3
mesece. Divje babe I. Naravna velikost
1 Od zgoraj
a = alveole za di^ g, b = alveola za dc, c - alveola za dg, d = alveola za d^, e =
2 Rentgenski posnetek leve mandibule od strani (izdelan na Kliniki za kirurgijo in male živali
Veterinarske fakultete v Ljubljani)
3 Shematska ponazoritev zametkov stalnih zob ^
Ontogenetic development of dentition in the cave bear
47
48_Irena Debeljak
Plate 4
Cave bear, right mandible (invt. num. 1033) of a female approx. 6-7 months old. Divje babe I.
Natural size
1 Lingual side
2 From above
a = alveolus of dc-C, b = alveolus of d,, c = alveolus of dg
3 Lateral x-ray photograph (made at tlie Clinic for surgery and small animals of the Veteri-
nary Faculty in Ljubljana)
4 Isolated molar M^; lingual side
5 Isolated molar М^; from below
Tabla 4
Jamski medved; desna mandíbula (inv. št. 1033) samice, stare okoli 6-7 mesecev. Divje babe I.
Naravna velikost
1 Lingvalna stran
2 Od zgoraj
a = alveola dc-C, b = alveola d^, c = alveola d,
3 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske
fakultete v Ljubljani)
4 Izoliran molar      lingvalna stran
5 Izoliran molar М^; od spodaj
Ontogenetic development of dentition in the cave bear
49
50_Irena Debeljak
Plate 5
Cave bear; left mandible of a male approx. 6.5-7.5 months old. Divje babe I. Natural size
1 Lingual side
2 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri-
nary Faculty in Ljubljana)
Tabla 5
Jamski medved; leva mandíbula samca, starega okoli 6,5-7,5 mesecev. Divje babe I. Naravna
velikost
1 Lingvalna stran
2 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske
fakultete v Ljubljani)
Ontogenetic development of dentition in the cave bear
51
52_Irena Debeljak
Plate 6
Cave bear; right mandible (invt. num. 1095) of a female approx. 6.5-7.5 months old. Divje babe I.
Natural size
1 Lingual side
2 Lateral x-ray photograph.     is isolated; lovi^er part of its root is sawn off. (x-ray was made
at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana)
3 Isolated molars     and Mg; lingual side
4 Isolated molars М^ and Mg; from below
Tabla 6
Jamski medved; desna mandibula (inv. št. 1095) samice, stare okoli 6,5-7,5 mesecev. Divje babe I.
Naravna velikost
1 Lingvalna stran
2 Rentgenski posnetek od strani. М^ je izoliran; spodnji del korenine je odžagan. (Posnetek je
bil izdelan na Kliniki za kirurgijo ш male živali Veterinarske fakultete v Ljubljani)
3 Izolirana molarja М^ in М^, lingvalna stran
4 Izolirana molarja М^ in M2; od spodaj

53
54_Irena Debeljak
Plate 7
Cave bear; left premaxilla and maxilla of a male approx. 6.5-7.5 months old. Divje babe I.
Natural size
1 Buccal side
2 Occlusal
3 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri-
nary Faculty in Ljubljana)
Tabla 7
Jamski medved; leva medčeljustnica in zgornja čeljustnica samca, starega okoli 6,5-7,5 mesecev.
Divje babe I. Naravna velikost
1 Bukalna stran
2 Okluzalno
3 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske
fakultete v Ljubljani)
Ontogenetic development of dentition in the cave bear
55
56_Irena Debeljak
Plate 8
1   Present-day brown bear; mandible (upper view) of a male approx. 10 months old. Natural
size
(Cub found on 28 Nov. 1989, about two weeks' decay.) LD Draga Trava - Loški potok. Collec-
tion of the Veterinary Faculty in Ljubljana (No. 178/89)
See also PL 10, fig. 1 (buccal side of the same specimen)
Tabla 8
1   Današnji rjavi medved; mandibula (slikana od zgoraj) samca, starega okoli 10 mesecev.
Naravna velikost
(Mladič najden 28. 11. 89, razpadal približno 2 tedna.) LD Draga Trava - Loški potok.
Zbirka Veterinarske fakultete v Ljubljani (št. 178/89)
Glej še tab. 10, si. 1 (bukalna stran istega primerka)
Ontogenetic development of dentition in the cave bear
57
58_Irena Debeljak
Plate 9
1   Recent brown bear; mandible (upper view) of a female approx. one year old. Natural size
(Cub killed on 26 Dec. 1986, weight 55 kg). Collection of the "Medved" breeding and hunting
ground, Kočevje
See also PL 10, fig. 2 (buccal side of the same specimen)
Tabla 9
1   Današnji rjavi medved; mandíbula (slikana od zgoraj) samice, stare okoli eno leto. Naravna
velikost
(Uplenjena 26. 12. 86, teža 55 kg.) Zbirka Gojitvenega lovišča "Medved", Kočevje
Glej še tab. 10, si. 2 (bukalna stran istega primerka)
Ontogenetic development of dentition in the cave bear
59
60_Irena Debeljak
Piatelo
1 Recent brown bear; buccal side of right mandible of a male approx. 10 months old. Natural
size
See also PI. 8 (upper view of the same specimen)
2 Recent brown bear; buccal side of left mandible of a female approx. one year old. Natural
size
See also PL 9 (upper view of the same specimen)
Tabla 10
1 Današnji rjavi medved; bukalna stran desne mandibule samca, starega okoli 10 mesecev.
Naravna velikost
Glej še tab. 8 (isti primerek od zgoraj)
2 Recentni rjavi medved; bukalna stran leve mandibule samice, stare okoli eno leto. Naravna
velikost
Glej še tab. 9 (isti primerek od zgoraj)
Ontogenetic development of dentition in the cave bear
61
62_Irena Debeljak
Plate 11
Cave bear; left mandible (invt. num. 1053) of a male approx. 12-15 months old. Divje babe I.
Natural size
1 Lingual side
2 From above
See also PI. 13, fig. 1 (lateral x-ray photograph of the same specimen)
Tabla 11
Jamski medved; leva mandíbula (inv. št. 1053) samca, starega okoli 12-15 mesecev. Divje babe I.
Naravna velikost
1 Lingvalna stran
2 Od zgoraj
Glej še tab. 13, si. 1 (lateralni rentgenski posnetek istega primerka)
Ontogenetic development of dentition in the cave bear
63
64_Irena Debeljak
Plate 12
Cave bear; left mandible (invt. num. 1385) of a female approx. 15 months old. Divje babe I.
Natural size
1 Lingual side
2 From above
See also PL 13, fig. 2 (lateral x-ray photograph of the same specimen)
Tabla 12
Jamski medved; leva mandibula (inv. št. 1385) samice, stare okoli 15 mesecev. Divje babe I.
Naravna velikost
1 Lingvalna stran
2 Od zgoraj
Glej še tab. 13, si. 2 (stranski rentgenski posnetek istega primerka)
Ontogenetic development of dentition in the cave bear
65
66_Irena Debeljak
Plate 13
1 Cave bear; left mandible (invt. num. 1053) of a male approx. 12-15 months old; lateral x-ray
photograph (made at the Clinic for surgery and small animals of the Veterinary Faculty in
Ljubljana)
See also PL 11, figs. 1, 2 (lingual side and upper view of the same specimen)
2 Cave bear; left mandible (invt. num. 1385) of a female approx. 15 months old; lateral x-ray
photograph (made at the Clinic for surgery and small animals of the Veterinary Faculty in
Ljubljana)
See also PL 12, figs. 1, 2 (lingual side and upper view of the same specimen)
Tabla 13
1 Jamski medved; leva mandíbula (inv. št. 1053) samca, starega okoli 12-15 mesecev; stranski
rentgenski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v
Ljubljani)
Glej še tab. 11, si. 1,2 (lingvalna in zgornja stran istega primerka)
2 Jamski medved; leva mandíbula (inv. št. 1385) samice, stare okoli 25 mesecev; stranski rent-
genski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v
Ljubljani)
Glej še tab. 12, si. 1, 2 (lingvalna in zgornja stran istega primerka)
Ontogenetic development of dentition in the cave bear
67
68_Irena Debeljak
Plate 14
Cave bear; left mandible (invt. num. 1428) of a female about one and a half years old. Divje babe I.
Natural size
1 Lingual side
2 From above
See also PL 15, figs. 1-3 (lateral x-ray photograph and isolated molars of the same specimen)
Tabla 14
Jamski medved; leva mandibula (inv. št. 1428) samice, stare okoli eno leto in pol. Divje babe I.
Naravna velikost
1 Lingvalna stran
2 Od zgoraj
Glej še tab. 15, si. 1-3 (stranski rentgenski posnetek in izolirani molarji istega primerka)
Ontogenetic development of dentition in the cave bear
69
70_Irena Debeljak
Plate 15
Cave bear; left mandible (invt. num. 1428) of a female about one and a half years old. Divje babe I.
Natural size
1 Lateral x-ray photograph. Mj is isolated; lower part of its root is sawn off. (x-ray was made
at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana)
2 Isolated molars and Mg; buccal side
3 Isolated molars М^ Mg and Mg; from below
See also PL 14, figs. 1, 2 (lingual side and upper view of the same specimen)
Tabla 15
Jamski medved; leva mandíbula (inv. št. 1428) samice, stare okoli eno leto in pol. Divje babe I.
Naravna velikost
1 Rentgenski posnetek od strani. M^^ je izoliran; spodnji del korenine je odžagan. (Posnetek je
bil izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani.)
2 Izolirani molarji М^ Mg in M3; bukalna stran
3 Izolirani molarji M^ M, in M,; od spodaj
Glej še tab. 14, si. 1,2 (lingvalna in zgornja stran istega primerka)
Ontogenetic development of dentition in the cave bear
71
72_Irena Debeljak
Plate 16
Present-day brown bear; right mandible of a male approx. one and a half years old. Natural size
(Found on 2 June 1992; killed by another bear). Kamenjak. Collection of the "Medved" breeding
and hunting ground Kočevje
1 From above
2 Buccal side
See also PI. 18, fig. 1 (lateral x-ray photograph of the same specimen)
Tabla 16
Današnji rjavi medved; desna mandibula samca, starega okoli eno leto in pol. Naravna velikost
(Najden 2. 6. 1992; ubit od drugega medveda.) Kamenjak. Zbirka Gojitvenega lovišča "Medved",
Kočevje
1 Od zgoraj
2 Bukalna stran
Glej še tab. 18, si. 1 (stranski rentgenski posnetek istega primerka)
Ontogenetic development of dentition in the cave bear
73
74_Irena Debeljak
Plate 17
Cave bear; left mandible (invt. num. 1094) of a male approximately 4 years old. Divje babe I
1 Lingual side. Reduction 2:1
2 Detail: tooth row P4-M3 from above. Natural size
See also PI. 18, fig. 2 (lateral x-ray photograph of the same specimen)
Tabla 17
Jamski medved; leva mandíbula (inv. št. 1094) samca, starega približno 4 leta. Divje babe I
1 Lingvalna stran. Pomanjšano 2:1
2 Izsek: zobna vrsta P4-M3 od zgoraj. Naravna velikost
Glej še tab. 18, si. 2 (stranski rentgenski posnetek istega primerka)
Ontogenetic development of dentition in the cave bear
75
76_Irena Debeljak
Plate 18
1 Present-day brown bear; right mandible of a male approx. one and a half years old; lateral x-
ray photograph (made at the Clinic for surgery and small animals of the Veterinary Faculty
in Ljubljana). Natural size
See also PL 16, fig. 1, 2 (upper view and buccal side of the same specimen)
2 Cave bear; left mandible (invt. num. 1094) of a male approx. 4 years old; lateral x-ray photo-
graph (made at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubl-
jana). Natural size
See also PL 17, fig. 1, 2 (lingual side and upper view of the same specimen)
Tabla 18
1 Današnji rjavi medved; desna mandibula samca, starega okoli eno leto in pol; stranski rent-
genski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljub-
ljani). Naravna velikost
Glej še tab. 16, si. 1,2 (zgornja in bukalna stran istega primerka)
2 Jamski medved; leva mandibula (inv. št. 1094) samca, starega približno 4 leta; stranski rent-
genski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v
Ljubljani). Naravna velikost