Received: 21 April 2021
Accepted for publication: 1 July 2021
Slov Vet Res 2021: 58 (3): 111 –16
DOI 10.26873/SVR-1330-2021
UDC 611.714.019:598.161.51+598.161.132 
Original Research Article
Introduction
Reptiles are a peculiar kind of animal 
characterized by corneous scales that protect 
them from desiccation (1). This class of animals 
is divided into four orders: Chelonians, which 
comprise turtles, tortoises, and terrapins; 
Crocodilla, whose specimens are alligators and 
crocodiles; Rhynchocephalia, with tuataras; and 
Squamate, represented by two suborders: Ophidia 
(snakes) and Lacertilia (lizards) (2). Some of these 
species have become very common in recent years 
as pets, which became a challenge for veterinary 
COMPARATIVE EVALUATION OF THE KOMODO DRAGON 
(Varanus komodoensis) AND THE GREEN IGUANA (Iguana iguana) 
SKULL BY THREE-DIMENSIONAL COMPUTED TOMOGRAPHIC 
RECONSTRUCTION
Sara Pérez1, Mario Encinoso1, Manuel Morales1, Alberto Arencibia2, Alejandro Suárez-Bonnet3, Eligia González-Rodríguez1, 
J. Raduan Jaber2*
1Instituto Universitario de Investigaciones Biomedicas y Sanitarias (IUIBS), 2Departamento de Morfologia, Facultad de Veterinaria, Universidad 
de Las Palmas de Gran Canaria. Trasmontaña, Arucas, 35413 Las Palmas, Spain, 3Department of Pathobiology, The Royal Veterinary College, 
University of London, Hertfordshire, AL9 7TA, London, United Kingdom
*Corresponding author, E-mail: joseraduan.jaber@ulpgc.es
Abstract: The purpose of this paper was to do a comparative evaluation of the skull of two species of lizards, the Komodo dragon 
(Varanus komodoensis) and the Green Iguana (Iguana iguana), by three-dimensional computed tomographic reconstruction. Im-
ages provided by this method give excellent anatomic detail of the skull. Therefore, essential differences in the configuration of the 
orbit and the lateral bones of the neurocranium were visualized in lateral and dorsal reconstructed images. The images obtained 
by tridimensional computed tomographic reconstruction can be a valuable diagnostic aid for the clinical evaluation of several 
head disturbances in lizards.
Key words: computed tomography; 3D reconstruction; anatomy; skull; lizards
clinicians since they have to overcome the lack 
of a reference system similar to canine and 
feline medicine (3). Thus, it is essential to know 
and understand their anatomy for an adequate 
diagnosis and treatment of diseases (4,5). 
The introduction of modern diagnostic imaging 
techniques such as x-ray computed tomography 
(CT) has been an essential support to specialists. 
It has afforded the chance to study anatomy and 
apply it in the clinical features of these species 
(6). Furthermore, compared with conventional 
radiography, the digital image format of CT results in 
improved tissue contrast. In addition, manipulation 
of the greyscale allows optimal visualization of all 
tissues within the slice. These characteristics are 
112 S. Pérez, M. Encinoso, M. Morales, A. Arencibia, A. Suárez-Bonnet, E. González-Rodríguez, J. R. Jaber
advantageous to obtain anatomical information 
about different regions of the animal body. The 
recent advances in CT technology include applying 
computer software to generate three-dimensional 
(3D) construction of an area of anatomic interest. 
This technique requires multiple thin section 
images, and the advantages of this process are 
that anatomical detail is improved, and can 
image bony structures with different degrees of 
rotation (6). CT reconstruction has already been 
used in morphofunctional studies performed 
in the Savannah monitor (7) and American 
Alligator (8). However, there are no reports 
concerning comparative anatomy of the skull of 
different species of reptiles by three-dimensional 
reconstructed CT to the author´s knowledge. The 
few descriptions performed in these species only 
deal with cross-sectional studies such as those 
done in the Boa constrictor (4), the Green iguana, 
the Common tegu, and the Bearded dragon head 
(5), and more recently, an anatomic interactive 
atlas of the loggerhead sea turtle head using 
images obtained via osteology, gross dissections, 
and computed tomography (9). Therefore, this 
study aimed to describe and compare the normal 
anatomy of two species of lizards, the Komodo 
dragon (Varanus komodoensis) and Green 
iguana (Iguana iguana) skull performing three-
dimensional CT reconstruction. 
Materials and methods
Animals
Two adult female Komodo dragons (Varanus 
komodoensis) and two male green iguanas 
(Iguana iguana) were imaged at the Veterinary 
Clinic Hospital of Las Palmas de Gran Canaria 
University. No physical examination abnormalities 
were detected before the study. The reptiles owner 
was informed of the study and signed consent for 
participation in it.
CT technique
Sequential transverse CT slices were obtained 
using a 16–slice helical CT scanner (Toshiba 
Astelion, Toshiba Medical System, Madrid, Spain). 
The animals were positioned symmetrically in 
ventral recumbency on the CT couch. A standard 
clinical protocol (120 kVp, 80 mA, 512 X 512 
acquisition matrix, 1809 x 858 field of view, a 
spiral pitch factor of 0.94, and a gantry rotation of 
1.5 s) was used to acquire sequential transverse 
CT images of 1 mm thickness slice. The original 
transverse data were stored and transferred to 
the CT workstation. No CT density or anatomic 
variations were detected in the head of the reptiles 
used in the investigation. In this study, we applied 
two CT windows by adjusting the window widths 
(WW) and window levels (WL) to appreciate the CT 
appearance of the head structures: a bone window 
setting (WW = 1500; WL = 300) and a soft tissue 
window setting (WW = 350; WL = 40). The original 
data were used to generate head volume-rendered 
reconstructed images after manual editing of the 
transverse CT images to remove soft tissues using 
a standard Dicom 3D format (OsiriX MD, Geneva, 
Switzerland). 
Results
Head three-dimensional volume-rendered re-
construction images corresponding to dorsal 
(Fig. 1, 4) and ventral (Fig. 2, 5) views and the 
left lateral view (Fig.3, 6) of the Komodo dragon 
and green iguana head. Volume-rendered recon-
structed CT images showed excellent visualization 
of the bones that comprised the skull. Therefore, 
in the Komodo dragon head, the orbit was cra-
nial and ventrally delimited by the lacrimal, the 
prefrontal, and the jugal bones (Figs. 1,3). Be-
sides, this technique allowed us to visualize the 
relation between this last and the ectopterygoid 
bone (Fig.3). Caudodorsally, the junction of the 
postorbital and postfrontal bones could be ob-
served in the lateral and dorsal reconstructed CT 
images (Figs. 1,3). Moreover, the ventral CT recon-
structed image identified the intersection of the 
frontal and the parietal bones. The different bones 
of the neurocranium, such as the parabasisphe-
noid, the basioccipital, and the prootic bones, 
were easily identifiable (Fig. 2). Besides, the lami-
nar disposition of the vomer and how it supports 
the septomaxilla were observed (Fig.2). The junc-
tion between the premaxilla and the maxilla with 
the tooth arranged in a straight row was identified 
in the lateral and ventral reconstructed CT im-
ages (Figs. 2,3). The jaw showed a straight tooth 
row and a curved ventral border in the lateral re-
constructed CT image. In addition, the coronoid 
process was quite prominent, and the surangu-
113Comparative evaluation of the Komodo dragon (Varanus komodoensis) and the Green iguana (Iguana iguana) skull by three-dimensional ...
lar and articular bones were observed extend-
ing caudally (Fig. 3). The ventral reconstructed 
image showed excellent pterygoid visualization, 
which is flat and “y” shaped bone. This one had a 
rounded process, where the caudal border of the 
palatine process contacts. This view also depicted 
the junction between the parabasisphenoid, the 
prootic, and the basioccipital bones. The ventral 
portion of this last bone constituted the occipital 
condyle (Fig. 2).
Figure 1: Three-dimensional volume-ren-
dered reconstruction image of the normal 
Komodo dragon head. Dorsal aspect. 
PM: Premaxillary bone. M: Maxillary 
bone. SM: Septomaxilla. N: Nasal bone. 
V: Vomer. PF: Prefrontal bone. F: Frontal 
bone. L: Lacrimal bone. J: Jugal bone. 
Q: Quadrate bone. Sq: Squamosal. PsF: 
Postfrontal+postorbital. P: Parietal.  PT: 
Pterygoid bone. SA: Surangular bone. C1: 
First cervical vertebra. C2: Second cervi-
cal vertebra
Figure 2: Three-dimensional volume-ren-
dered reconstruction image of the normal 
Komodo dragon head. Ventral aspect. 
D: Dentary bone. SA: Surangular bone. 
A: Articular bone. SM: Septomaxilla. V 
Vomer. PL: Palatine bone. PT: Pterygoid 
bone. PsF: Postfrontal+postorbital bone. 
N: Nasal bone. F: Frontal bone. P: Pari-
etal bone. PB: Parabasisphenoid bone. 
BO: Basioccipital bone. OC: Occipital 
condyle. PRO: Prootic bone. Q: Quadrate 
bone.
Figure 3: Three-dimensional volume-ren-
dered reconstruction image of the normal 
Komodo dragon head. Lateral aspect. 
PM: Premaxillary bone. M: Maxillary 
bone. PF: Prefrontal bone. N: Nasal 
bone. F: Frontal bone. L: Lacrimal bone. 
J: Jugal bone. Ec: Ectopterygoid bone. 
Pt: Pterygoid bone. EPt: Epipterygoid. Q: 
Quadrate bone. St: Supratemporal. Sq: 
Squamosal. PsF: Postfrontal+postorbital. 
PRO: Prootic. PB: Parabasisphenoid 
bone. P: Parietalbone. D: Dentary bone. 
C: Coronoid bone. SA: Surangular bone. 
Sp: Splenial. PRa: Retroarticular process. 
EcD: Osteoderms
114 S. Pérez, M. Encinoso, M. Morales, A. Arencibia, A. Suárez-Bonnet, E. González-Rodríguez, J. R. Jaber
Concerning the green iguana head, the lateral 
reconstructed images showed a high and domed 
skull (Fig. 6). In contrast with the Komodo dragon 
head, the orbit of the green iguana was closed by 
the postfrontal and the postorbital bone junction, 
which was extended to the posterior margins of bony 
orbits till articulate with the jugal bone (Figs. 4,6). 
Therefore,  the jugal formed the lateral wall of the 
bony orbit and was joined with lacrimal (dorsally), 
maxillary (ventrally), ectopterygoid (medially), 
postorbital (caudodorsally), and squamosal 
(caudally) (Fig. 6). This view identified frontal, 
parietal, and postfrontal bones (Fig. 6). Moreover, 
the prefrontal bones connecting rostrally maxillary 
and nasal bones, laterally to lacrimal bones, and 
caudodorsally to frontal bones were also identified 
in the dorsal view (Fig. 4). This prefrontal bone 
participated in the dorsal and rostral orbit walls 
(Figs. 4,6). This lateral view showed the junction 
between squamosal, ectopterygoid, epipterygoid, 
pterygoid, quadrate, and prootic bones. This 
last one had a square shape and formed the 
neurocranium’s lateral walls, which were also well 
visualized in ventral reconstructed images (Fig. 5). 
Thus, the junction between the basioccipital, the 
parabasisphenoid bones, and its lateral connection 
with the pterygoid could be observed. These ventral 
and lateral reconstructed images showed the 
bones composing the jaw. Thus, the dentary, the 
coronoid, the surangular, and the articular bones 
were evident in these views.
Figure 4: Three-dimensional volume-rendered reconstruction 
image of the normal Green iguana head. Dorsal aspect. PM: 
Premaxillary bone. M: Maxillary bone. N: Nasal bone. PF: 
Prefrontal bone. F: Frontal bone. J: Jugal bone. Q: Quadrate 
bone. Sq: Squamosal. PsF: Postfrontal. PsO: Postorbital. 
P: Parietal. SP: Supraoccipital bone. D: Dentary bone. A: 
Articular bone
Figure 5: Three-dimensional volume-rendered reconstruction 
image of the normal Green iguana head. Ventral aspect. D: 
Dentary bone. SA: Surangular bone. A: Articular bone. PM: 
Premaxillary bone. V Vomer. PL: Palatine bone. PT: Pterygoid 
bone. PB: Parabasisphenoid bone. BO: Basioccipital bone. Q: 
Quadrate bone. OC: Occipital condyle. HA: Hyoid apparatus
Figure 6: Three-dimensional volume-rendered reconstruction 
image of the normal Green iguana head. Lateral aspect. PM: 
Premaxillary bone. M: Maxillary bone. PF: Prefrontal bone. 
N: Nasal bone. F: Frontal bone. OB: Orbit. L: Lacrimal bone. 
J: Jugal bone. PsF: Postfrontal bone. PsO: postorbital bone. 
PT: Pterygoid bone. EPt: Epipterygoid. Q: Quadrate bone. Sq: 
Squamosal. PRO: Prootic. P: Parietal bone. D: Dentary bone. 
C: Coronoid bone. SA: Surangular bone. A: Articular bone. HA: 
Hyoid apparatus
Discussion
The arrival of imaging techniques to reptile 
medicine has improved veterinary medicine 
diagnosis (5-9). Traditionally, radiography (10) 
115Comparative evaluation of the Komodo dragon (Varanus komodoensis) and the Green iguana (Iguana iguana) skull by three-dimensional ...
and ultrasonography (11) have been applied to 
obtain information on the bony and the main soft-
tissue structures of different animal regions. In 
contrast, computed tomography has become the 
preferred imaging technique due to its considerable 
advantages (11). Hence, last-generation CT 
equipment gives fast imaging acquisition, body 
sections from different tomographic planes, fair 
anatomic resolution without superimposition, 
and excellent tissue-like differentiation (5,9). 
Three-dimensional CT reconstruction is a 
valuable procedure, which is infrequently applied 
in veterinary medicine. The data collection 
requires multiple parallel thin sections, which 
are all obtained at the same gantry tilt. Ideally, a 
high-speed scanner such as the scanning beam 
‘cine’ CT system can produce a rapid sequence of 
quality thin sections to minimize motion artifact 
(12). This procedure can image the surface of 
bony structures with different degrees of rotation 
without the superimposition of soft tissues 
(12,13,14).
As in other lizards, the Komodo dragon and 
the Green Iguana skull are complex structures 
composed of different bones with significant 
disparity. However, in contrast with other reports 
that did radiographs (4,5), the use of reconstructed 
images of the skull avoided the superimposing 
of the bilateral structures of the snout and 
neurocranium to give excellent visualization of 
the junction between bones that comprise the 
head. Thus, lateral and dorsal reconstructed 
images visualized essential differences between 
the species studied. Therefore, an enormous 
difference in the orbit composition was observed in 
the species studied, especially along the posterior 
margin of the orbit, where it was closed (Green 
iguana) or open (Komodo dragon). This fact was 
determined by variations in the shape, size, and 
presence of the jugal bone and variations in the 
postorbital and postfrontal bones, as explained 
by Daza and Bauer (15). Besides, in the lateral 
side of the neurocranium could be identified the 
prootic bone, which had a square shape in the 
Green iguana. In contrast, it was tubular in the 
Komodo dragon.
Other investigations have studied the compar-
ative and morphometrics features of the skull in 
terrestrial mammals by three-dimensional com-
puted tomographic reconstruction (16). Nonethe-
less, in our study, anatomical measurements of 
the head and mandible were not performed since 
the number of specimens studied was scarce to 
perform statistical analysis.
 In conclusion, we have attempted to describe 
our findings on recognizable structures in alive 
reptiles, but further studies are necessary to define 
the ultimate limits of 3D CT reconstruction for 
essential morphologic imaging and interpretation 
of animals with clinical signs. Nevertheless, the 
CT reconstructed images obtained in this study 
facilitated an adequate anatomical understanding 
of the Komodo dragon and Green iguana skull. This 
information could be used to diagnose disorders 
involving the head of lizards, such as metabolic 
bone diseases, fractures, and neoplasias. 
Acknowledgment 
In loving memory of Alvaro Domingo Rodriguez 
Garcia. We also thank Marisa Mohamad for her 
support and constructive comments.
Authors declare that no any conflict of interest 
exists. 
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PRIMERJAVA LOBANJ KOMODOŠKEGA VARANA (Varanus komodoensis) IN 
ZELENEGA LEGVANA (Iguana iguana) S POMOČJO TRIDIMENZIONALNE  
RAČUNALNIŠKE TOMOGRAFSKE REKONSTRUKCIJE
S. Pérez, M. Encinoso, M. Morales, A. Arencibia, A. Suárez-Bonnet, E. González-Rodríguez, J. R. Jaber
Izvleček: Namen prispevka je bil s tridimenzionalno računalniško tomografsko rekonstrukcijo opraviti primerjalno oceno 
lobanje dveh vrst kuščarjev, komodoškega varana (Varanus komodoensis) in zelenega legvana (Iguana iguana). Slike, pri-
dobljene s to metodo, prikažejo odlične anatomske podrobnosti lobanje. Zato so bile na stranskih in dorzalnih rekonstrukcijah 
slik vidne bistvene razlike v zgradbi orbitalnega področja in stranskih kosti nevrokranija med obema vrstama kuščarjev. Slike, 
pridobljene s tridimenzionalno računalniško tomografsko rekonstrukcijo, so lahko dragocena diagnostična pomoč pri klinični 
oceni večih napak glave pri kuščarjih.
Ključne besede: računalniška tomografija; 3D rekonstrukcija; anatomija; lobanja; kuščarji