GEOLOGIJA 37, 38, 123-140 (1994/95), Ljubljana
Preliminary biometrical analysis on three similar hippuritid
species
Mauro Caffau
Dipartimento di Scienze Geologiche Ambientali e Marine, Università degli Studi di Trieste,
Via Eduardo Weiss 2 CAP 34127 Trieste
Mario Pleničar
Katedra za geologijo in paleontologijo NTF
Univerza v Ljubljani
Aškerčeva 2, 1000 Ljubljana, Slovenija
Abstract
The hippuritids species Hippuritella lapeirousei (Goldfuss, 1840), Hippu-
ritella nabresinensis (Futterer, 1893) and Hippuritella heritschi (Kühn, 1947)
vigere studied through biometrical analysis. For this purpose, the areas of three
morphological characters which are related by their biological functions (as de-
scribed by Realy, 1992) were measured on transversal sections of lower valves.
These morphometrical values are: a) shell area (Sa), b) inner area (la) and c)
pillars area (Pl-P2a). This analysis highlighted a morphological similarity between
HI. nabresinensis and HI. heritschi, meanwhile the morphometric values for HI.
lapeirousei showed to be different.
Introduction
The hippuritid species Hippuritella lapeirousei (Goldfuss, 1840), Hippuritel-
la nabresinensis (Futterer, 1893) and Hippuritella heritschi (Kühn, 1947) are very
similar from the morphological point of view^. In fact, this topic was discussed in li-
terature by different authors.
Douvillé (1891-97) observed a clear similarity betv^een HI. lapeirousei and HI.
nabresinensis and, later, Parona (1900) and Toucas (1903-1904) considered HI.
nabresinensis as a synonim of HI. lapeirousei. Hov^^ever several authors observed
a w^ide variability in the ornamentation of these species. Toucas (1903-1904) no-
ted it analysing the lower valve of HI. lapeirousei. Successively, Pleničar (1975,
1994) and Vic ens (1992) observed this variability between HI. nabresinensis and
HI. lapeirousei. Afterwards, Sladić-Trifunović (1972, 1978) and Laviano (1985)
discussed the problem about the great similarity among the three species.
Thus, their similarity focuses on a still unsolved taxonomical problem. The aim
of this paper is to discuss about this taxonomical problem through morphometric analysis
carried out on specimens belonging to the three species.
124	Mauro Caffau & Mario Pleničar
Material
Part of the morphometrical measures was obtained analysing the specimens of
HI. Lapeirousei, HI. Nabresinensis and HI. heritschi described in literature, including
the holotypes of the three species (tables 1, 2, 3). Moreover, 300 lower valves of HI.
nabresinensis coming from the area of the holotype (Aurisina/Nabrežina - Karst of
Triest) have been analyzed (table 4). Forty-eight of them were selected in that they
revealed an excellent state of conservation. Fifteen valves of HI. heritschi coming
from Stranice and Senožeče (Slovenia) have been analysed and measured. These samples
show similar morphological characters with respect to those of the holotype descri-
bed by Kühn (1947).
Unfortunately it was no possible to carry out similar analysis with specimens of
HI lapeirousei, because in the area of the Karst of Trieste (Italy) and Triest-Ko-
men plain (Slovenia) this species is represented by scarce and bad-preserved speci-
mens.
The studied valves of HI. nabresinensis and HI. heritschi are deposited in the
collection of the "Istituto di Geologia e Paleontologia dell'Università di Trieste", and
in the collection of the "Katedra za geologijo in paleontologijo univerze v Ljubljani",
respectively, meanwhile those coming from Senožeče (Slovenia) have been kindly lent
by doctor Bogdan Jurkovšek from his private collection.
The systematics and taxonomic aspects of the three species are shortly discussed be-
low.
Palaeontological description
Familia Hippuritidae Gray, 1848
Genus Hippuritella Douvillé, 1908
Hippuritella lapeirousei (Goldfuss, 1840)
1891-97 Hippurites lapeirousei var. crassa Goldfuss - Douvillé, 222, pl. 24, fig.
10.
1900 Hippurites lapeirousei Goldfuss -Parona, 11, pi. 1, figs. 1-3.
1912 Orbignya lapeirousei var. crassa Goldfuss - Schubert, 62.
1975 Hippurites (Orbignya) lapeirousei Goldfuss - Pleničar, 87, pl. 1, fig. 10.
1981 Hippuritella lapeirousei (Goldfuss) - Sánchez 10, cum syn.
1992 Hippuritella lapeirousei (Goldfuss) - Vicens, 123.
1994 Hippuritella lapeirousei (Goldfuss) - Pleničar, 50, pl. 2, figs 9-10.
Taxonomical remarks: According to Douvillé (1891-97), lapeirousei
is characterized by a cylindrical or cylindric-conical lower valve ornamented by
longitudinal costae of variable wideness, which are separated by concave rounded canals.
The distance between the costae varies among specimens coming from different
geografical areas. The upper valve is covered by polygonal pores, which are arranged
into regular and radial rows on the border of the valve.
The inner characters are the ligamental ridge, absent or hardly marked by a small
inflexion in the outer layer of the shell, and the rounded pillars, which are slightly
different between them. The cardinal apparatus is situated near the dorsal margin
of the lower valve. The tooth N is X-shaped. The narrow and elongated alveolus of
Preliminary biometrical analysis on three similar hippuritid species	125
the anterior tooth is situated along the dorsal margin, while that of the posterior one
is small and rounded. The miophore cavities are well developed.
Douvillé (1895) observed that "les caractères de l'ornamentation extérieure,
quoique d'une importance beaucoup moindre, peuvent être aussi d'une certain utilité
pour distinguer ces espèces."
Douvillé (1895) defined the group of Hippuritella variabilis Munier-Chalmas,
1867 in which he included the following species: Hippuritella maestrei Vidal, 1878,
Hippuritella variabilis and Hippuritella lapeirousei.
Sladić-Trifunović (1978) observed that the holotype of HI. lapeirousei is
characterized by a conical valve, while the holotype of HI. nabresinensis is cylindrical.
Distribution: This species has been found in the Upper Campanian-Lower Maas-
trichtian in Spain in the areas of Montsec and Valencia, in Italy in the zones of Mátese
Mt. And Maiella Mt. (Pons & Sima, 1992) and at Stranice in the Maastrichtian
(Slovenia) (Pleničar, 1994).
The transversal sections of the lower valves of the individuals of the species
Hippuritella lapeirousei are presented on the plate 1, the morphometrical measures
of the same individuals on the table 1.
Hippuritella nabresinensis (Futterer, 1893)
1926 Hippurites (Orbignya) lapeirousei Goldfuss - Parona, 349.
1969 Hippurites nabresinensis acuticostatus Lupu - Lupu, 210, pl. 1.
1975 H. (Orbignya) nabresinensis Futterer - Pleničar, 107, pl. 1, fig. 2., textfig. 3.
1981	H. nabresinensis Futterer - Sánchez, 20, cum syn.
1982	H. nabresinensis Futterer - Czabalay, 80, pl. 10, fig. 5.
1982 H. nabresinensis Futterer - Accordi et al., 770, pl. 7, figs. 8, 10.
1985 H. nabresinensis Futterer - Laviano, 325, pl. 7, figs. 2, 4.
1992 H. nabresinensis Futterer - Peza, 294, pl. 1, fig. 3.
Table 1. Morphometrical measures of samples of Hl. lapeirousei described in literature
Sa Shell area; la Inner area; Pl-P2a Pillars area. The area's values are expressed in mm^
126	Mauro Caffau & Mario Pleničar
Taxonomical remarks: Futterer (1893) in the description of the Hl. nabre-
sinensis focused his attention specially on the external characters of this species.
He described the cylindrical lower valve with a length of 270 mm and a diameter of
30 to 40mm. The shell is crossed by about 21 longitudinal and rounded costae, which
are from 2 to 5mm wide. The pillar PI is rounded and its base is wider than that of
the pillars P2. Accordi et al. (1982) observed that the shell is crossed by rounded
costae which include narrow canals. These canals are also crossed by thin ribs. The
external shell presents weak concavities in correspondence to the pillars. The pres-
ence of a ligamental ridge is not mentioned by Futterer (1893) in his description
of the holotype. This character is confirmed by personal observations on 300 lower
valves of this species coming from the type locality Aurisina/Nabrežina.
The Futterer's description (1893) receives two years later the first objection
from Douvillé (1895), who placed HI. nabresinensis as a synonym of Hippurites
lapeirousei var. crassa because these characters were not enough to create a new
species. Parona (1900) also observed the great similarity between HI. nabresinensis
and HI. lapeirousei and the same author placed HI. nabresinensis as a synonym
of HI. lapeirousei in 1926 confirming the previous observations of Douvillé (1895).
Also Schubert (1912) placed HI. nabresinensis as synonym of HI. lapeirousei var.
crassa.
Kühn (1947) described a new species HI. heritschi. Later, other authors discussed
about the simñarity between these species: Sladić-Trifunović (1972, 1978) analysed
the taxonomical problem and L avian o (1985) summarized the observations about
the differences between the three species, according to the previous authors (Lupu,
1976; Sladić-Trifunović, 1972, 1978; Accordi et al., 1982).
Distribution: the holotype described by Futterer (1893) has been found in
the type locality Aurisina/Nabrežina (Karst of Trieste) in the limestones of the Santonian-
Campanian (Cucchi et al., 1987).
The transversal sections of the lower valves of the individuals of the species
Hippuritella nabresinensis are presented on the plates 2, 3a and 3b, the mor-
phometrical measures of the same individuals on the tables 2 and 3.
Table 2. Morphometrical measures of samples of HI. nabresinensis described in literature
Sa Shell area; la Inner area; Pl-PSa Pillars area. The area's values are expressed in mm^
Preliminary biometrical analysis on three similar hippuritid species	127
Table 3. Morphometrical measures of samples of HI. nabresinensis coming from to
Aurisina/Nabrežina (Karst of Trieste)
Sa Shell area; la Inner area; Pl-Pêa Pillars area. The area's values are expressed in mm^
Hippuritella heritschi (Kühn, 1947)
1908 Hippurites colliciatus Woodward - Schmidt, 238.
1934 Hippurites (Orbignya) lapeirousei Goldfuss - Milovanović, 223, fig. 18.
1951 H. (Orb.) nabresinensis Futterer - Pejović, 94, pl. 1, fig. 2; pl. 2, fig. 2; pl. 3,
fig. 2.
1960 H. heritschi Kühn - Kühn, 48.
1962 H. heritschi Kühn - Kaumanns, 305, pl. 2, fig. 4; text. fig. 6.
1970 H. heritschi Kühn - Pamouktchiev, 48.
1978	H. heritschi Kühn - Sladić-Trifunović, 422, pl. 1-8, text. fig. 1, 2.
1979	Hippuritella heritschi (Kühn) - Pamouktchiev, 220, pi. 7, figs. 1-3.
1982 Hippurites heritschi Kühn - Czabalay, 79, pi. 13, fig. 14; pi. 18, fig. 1.
1992 Hippurites heritschi Kühn - Caffau et al.. Pl. 1, fig. 1.
1994 Hippuritella heritschi (Kühn) - Pleničar, 51, pl. 2, fig. 7; pl. 3, fig. 1, 2.
Taxonomical remarks: the conical lower valve is crossed by longitudinal costae,
separated by rounded canals. In some specimens the shell is very thick and can be
as large as 27mm, as described by Sladić-Trifunović (1978). The pillars are
128	Mauro Caffau & Mario Pleničar
triangular with approximately the same dimensions. The upper valve, which was
described for the first time by Sladić-Trifunović (1978), is covered by polygonal
pores and radially crossed by canals. The ligamental ridge is absent. Sladić-
Trifunović (1978) analysed the taxonomical problem concerning the similarity of
this species with the HI. lapeirousei and HI. nabresinensis. He also observed that
in all stages of the ontogenetical development, the shell of HI. heritschi is always
thick. In our opinion, such character is also present in HI. nabresinensis. According
to Pejović and Kühn (1960), Laviano (1985) considered the shape and dimension
of the shell and pillars as distinctive characters between HI. nabresinensis and HI.
heritschi.
Table 4. Morphometrical measures of samples of HI. heritschi described in literature
Sa Shell area; la Inner area; Pl-P2a Pillars area. The area's values are expressed in mm^
Table 5. Morphometrical measures of samples of HI. heritschi from Stranice (samples 1-2)
and from Senožeče (samples 3-15), Slovenia
Sa Shell area; la Inner area; Pl-PSa Pillars area. The area's values are expressed in mm^
Preliminary biometrical analysis on three similar hippuritid species	129
Disribution: HI. heritschi was found in Maastrichtian in Katschberg, near the
St. Bartholomä in Austria (Sladić-Trifunović, 1978). Furthermore, in the Upper
Campanian-Lower Maastrichtian in the zone of Valencia in Spain, in Italy in the
Apennines in the zone of Maiella Mt. and Mátese Mt. and in Sicilia (Pachino) (Pons
& Sima, 1992).
The transversal sections of the lower valves of the individuals of the species
Hippuritella heritschi are presented on the plates 4 and 5, the morphometrical
measures of the same individuals on the tables 4 and 5.
Biometrical analysis
We recall that the examined material for this study included: a) specimens which
are already described in literature and b) specimens coming from different outcrops
(tab. 3a, 3b, 5; pi. 3, 5).
In the first case, the morphometrical values were obtained from published
illustrations (tab. 1, 2, 4; pi. 1, 2, 4). In the latter case, the lower valves were cut
and their transversal sections were subjected to morphometric measurements. Some
characters, which are related by their biological functions (Reali, 1992) were selected
for this biometrical study and their areas were measured as shown in Fig la. These
morphometrical values are: a) the surface mantle or shell area (5a) responsible for
the incoming water flux and the entrance of nutrients in the internal cavity; b) the
area of the internal cavity (la) which contains the organic tissues where assimilation
of nutrients takes place; c) the surface of pillars (Pl-P2a), related to the expulsion
of metabolic residues. Taking into acount that pillars and mantle thickness are in close
biological relationship with the internal cavity (Skelton, 1976J, Pl-P2a and Sa values
were plotted against la.
Fig. la. Transversal section of a
lower valve where the measured
areas are indicated
130	Mauro Caffau & Mario Pleničar
In ali the graphs, the regression lines corresponding to Hl. lapeirousei, Hl. nabre-
sinensis and HI. heritschi were indicated as a, b, and c, respectively.
Results and fìnal consideration
In all the cases, the regression lines of Sa versus la and Pl-P2a versus la (figs.
1-4) have a dispersion coefficient (r squared = R) close to the unit.
This values indicates a very good correlation between these morphological
characters, also including specimens coming from different geographical areas. In detail,
in graph fig. 1 the slope of the regression lines for the species HI. nabresinensis
and HI. heritschi are 0.85 and 0.91 respectively while for HI. lapeirousei is 0.59.
In graph fig. 2, the regression lines for HI. nabresinensis and HI. heritschi have
a slope of 0.059 and 0.057 respectively while for HI. lapeirousei is 0.046. Comparing
these values (graphs figs. 1 and 2) it can be seen that the slope of the regression
line for the species HI. lapeirousei differs from the other two, which are very similar
between them.
The same values for the collected samples of the species HI. nabresinensis and
HI. heritschi (graph fig. 3: slope values of 1.03 and 0.87 respectively) are very similar
Fig. 1. Shell area (Sa) versus inner area (la) of samples of the three
described in literature (see data on tables 1, 2, 4). Regression values
and disperssion coefficient are shown
Preliminary biometrical analysis on three similar hippuritid species	131
Fig. 2. Pillars area (Pl-P2a) versus inner area (la) of samples of the three
described in literature (see data on tables 1, 2, 4). Regression values and
disperssion coefficient are shown
to those of the specimens described in literature (graph fig. 1: 0.85 and 0.91 respec-
tively). The same can be said comparing the slope of the regression lines in graphs
figs. 4 and 2.
Thus, combining the results from the analysis of the specimens described in
literature and those collected, it is possible to conclude that the biological characters
of HI. lapeirousei are clearly different from those of the other tv^o species. On the
contrary, the characters of HI. nabresinensis and HI. heritschi are very simüar betM^een
them. This fact leads to the idea that these tv^^o species could be the same. In fact,
newf morphometrical analysis are in process in order to confirm this hypothesis.
Acknowledgements
This viTorks has been carried out with the grant of the Chair for Geology and
Paleontology of the University in Ljubljana, of the Slovene Academy of Sciences and
Arts and of Istituto di Geologia e Paleontologia dell'Università di Trieste. We are
particulary indebted to Dr. Bogdan Jurkovšek, who kindly lent us some rudist samples
from his collection and to Dr. Maria Inés Gutiérrez of I.C.G.B, for translation into English.
132	Mauro Caffau & Mario Pleničar
Fig. 3. Shell area (Sa) versus inner area (la) of samples of Hl. nabresin-
ensis and Hl. heritschi recently found in outcrops (see data on tables 3,
5). Regres-sion values and disperssion coefficient are shown
We are very grateful to Prof. Nevio Pugliese of Università di Trieste for his useful
suggestions and for reading critically the manunscript.
Warmest thanks are extended to all.
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Preliminary biometrical analysis on three similar hippuritid species	135
Plate 1
HI. lapeirousei, transversal sections of lower valves of individuals described in literature,
measured and numbered. Bar scale: 10mm
136	Mauro Caffau & Mario Pleničar
Plate 2
Hl. nabresinensis, transversal sections of low^er valves of individuals described in litera-
ture, measured and numbered. Bar scale: 10mm
Preliminary biometrical analysis on three similar hippuritid species	137
Plate 3 a
HI. nabresinensis, transversal sections of the lower valves of individuals that belong to
Aurisina/Nabrežina (Karst of Trieste), measured and numbered. Bar scale: 20mm
138	Mauro Caffau & Mario Pleničar
Plate 3b
Hl. nabresinensis, transversal sections of the low^er valves of individuals that belong to
Aurisina/Nabrežina (Karst of Trieste), measured and numbered. Bar scale: 20mm
Plate 4
Hl. heritschi, transversal sections of lower valves of individuals described in literature,
measured and numbered. Bar scale: 20mm
140	Mauro Caffau & Mario Pleničar
Plate 5
Hl. heritschi, transversal sections of lower valves of individuals from Stranice (samples 1-2)
and fromSenožeče (samples 3-15) measured and numbered. Bar scale: 20mm