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Submitted 13 September 2019
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Davit Vasilyan,
davit.vasilyan@jurassica.ch
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Andrew Farke
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DOI 10.7717/peerj.8322
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OPEN ACCESS
The fossil record of the genus Varanus
from the Southern Caucasus (Armenia,
Georgia)
Davit Vasilyan1,2and Maia Bukhsianidze3
1JURASSICA Museum, Porrentruy, Switzerland
2Department of Geosciences, University of Fribourg, Fribourg, Switzerland
3Georgian National Museum, Tbilisi, Georgia
ABSTRACT
The Southern Caucasus, with its special geographic position and complex topography,
is a well-known biodiversity hotspot. However, the formation of this hotspot remains
largely unstudied. To reveal this, a thorough study of the fossil record of the region
is necessary. In the present paper, we describe for the first time fossil monitor lizards
(Varanus sp.) from two late Miocene localities from the Southern Caucasus (Jradzor,
Armenia and Tetri Udabno, Georgia). We suggest that both fossils belong to a small-
sized monitor lizard, comparable to the present-day species found in Iran and the
Middle East (e.g., Iraq, Saudi Arabian)—the most western part of the extant monitor
lizards’ Eurasian distribution range. Our finds show that the genus had a broad
distribution in the Eastern Paratethyan region during the late Miocene. In addition,
we provide the probable temperature ranges for fossil localities.
Subjects Biodiversity, Paleontology, Zoology
Keywords Varanus, Late Miocene, Southern Caucasus, Armenia, Georgia, Palaeobiogeography,
Palaeoclimate
INTRODUCTION
The Southern Caucasus is characterized by diverse biomes ranging from humid subtropical
evergreen forests to dry steppe with numerous endemic plant and animal species
(Nakhutsrishvili et al., 2015). Biotic diversity has been shaped on one hand by the
topography of the region with their characteristic weather zones and on another hand
due to the geographic position of the region at the crossroad of Europe, Asia and Africa.
Due to the limited number of palaeontological studies in the region, the evolutionary
history of these unique ecosystems and endemic forms remains largely unknown.
Though the history of the flora and fauna—molluscs, mammals, of the region were under
the main focus of earlier studies (e.g., Hakopyan, 1974;Bukhsianidze & Koiava, 2018), other
groups, e.g., such as the insects, amphibians and reptiles received less attention. Studies
on the Neogene continental ectothermic vertebrate of the area are mainly limited to the
turtles (Chkhikvadze, 1983;Chkhikvadze, 1989), whereas amphibian, crocodilian and snake
(Gabunia, 1964;Chkhikvadze, 1984) remains are very scarce, as a result of the lack of rich
fossil accumulations or insufficient excavation/or exploration.
How to cite this article Vasilyan D, Bukhsianidze M. 2020. The fossil record of the genus Varanus from the Southern Caucasus (Armenia,
Georgia). PeerJ 8:e8322 http://doi.org/10.7717/peerj.8322
In comparison to other regions of Western Eurasia, such as Anatolia, Eastern or Central
Europe, the fossil record of Southern Caucasus is extremely poorly studied. This hinders
on one hand the ability to trace the evolution of the local fossil record and the roots of
the present-day unique ecosystems and endemic forms, but on another hand, it makes
impossible any palaeobiogeographic comparison of the Southern Caucasian record with
the other regions of Eurasia. This aspect has a crucial importance considering the key
geographic location of the region.
In the present paper, we report the first fossil record of the genus Varanus from Southern
Caucasus. We discuss and compare the fossil record of the genus with other similar age
localities (Fig. 1,Table 1).
Geological settings
Jradzor, Armenia
The studied material comes from the fossiliferous horizon JZ-3 of the Jradzor section in
Central Armenia. The horizon is composed of clayey sand, representing an accumulation
of weathering products from the surrounding volcanic rocks. Besides the monitor
lizard remains, a rich vertebrate faunal assemblage has been discovered, which includes
amphibians, reptilian, avian as well as mammalian remains (Vasilyan et al., 2018). The
biochronology of small mammalian species from JZ-3 correlates the assemblage to the
latest Miocene (latest MN13).
Tetri Udabno, Georgia
The fossils were found in the Tetri Udabno, one of the localities of the Udabno Site, Georgia,
located in the most eastern part of the Udabno Syncline. So far, fossil vertebrates from this
locality where known from the Shiraki Formation (Maeotian) (Bukhsianidze & Koiava,
2018). These fossil specimens come from the underlying Eldari Formation, continental
deposits developed in the Middle Kura Basin, largely correlated with the Khersonian
marine regional stage of the Eastern Paratethys. The monitor lizard remains were found in
grey silty clays. So far, they are the only fossils found from the layer, yet, recently a large
number of sporadically distributed vertebrate fossils on different stratigraphic levels in
these deposits were revealed.
MATERIALS & METHODS
The studied material represents partially articulated or disarticulated postcranial and jaw
material found during the excavation/prospecting in 2017 in Georgia and 2018 in Armenia.
The field work in Georgia has been provided by Maia Bukhsianidze, Georgian National
Museum, whereas in Armenia it was undertaken by Davit Vasilyan, with support of the
Institute of Geological Sciences, National Academy of Sciences of Republic of Armenia.
The material has been photographed using a digital microscope (Leica DVM5000) and
also a NIKON D610 camera. The terminology of Villa et al. (2018) has been used for the
description of the fossil material. The measurements of the vertebrae follow those of Holmes
et al. (2010) and Hocknull et al. (2009), which is indicated accordingly in the Table 2. The
body length estimations have been calculated according to the ratio of snout-vent length
Vasilyan and Bukhsianidze (2020), PeerJ, DOI 10.7717/peerj.8322 2/12
Black Sea
Caspian Sea
4
16
19
21
10 20
2, 4
5
6
Bessarabian and Maeotian shoreline of the Eastern Paratethys Map data © 2019 Google
Figure 1 The map of the Eastern Paratethys with the known (in yellow) and herein described (in red) fossil occurrences of the genus Varanus.
The numbers next to the fossil localities correspond to the locality numbers of the Table 1. Map data c
2019 Google.
Full-size DOI: 10.7717/peerj.8322/fig-1
(SVL)/vertebra length (Hocknull et al., 2009) introduced in Conrad, Balcarcel & Mehling
(2012). The body size estimations have been calculated only based on the vertebrae for
which the vertebral length Hocknull et al. (2009) can be measured. The material is stored
in the palaeontological collections of the Institute of the Geological Sciences, National
Academy of Sciences of Republic of Armenia, Yerevan, Armenia (IGS) and S. Janashia
Museum of Georgia, Georgian National Museum, Tbilisi, Georgia (GNM1).
RESULTS
Systematic palaeontology
Clade Squamata Oppel, 1811
Clade Anguimorpha Fürbinger, 1900
Family Varanidae Gray, 1827
Genus Varanus Merrem, 1820
Varanus sp.
(Fig. 2)
Material
One right dentary (IGS JRD-18/12) and one trunk vertebra (IGS JRD-18/13), Jradzor
locality, horizon JZ-3, late Miocene, late Messinian, late MN13, Armenia. Ten trunk
vertebrae (GNM1 32-2013/1107-a – -f) and three limb bones (GNM1 32-2013/1107-g –
-i), locality Tetri Udabno, late Miocene, late Tortonian, Khersonian, Georgia.
Vasilyan and Bukhsianidze (2020), PeerJ, DOI 10.7717/peerj.8322 3/12
Table 1 Late Miocene record of the genus Varanus from Western Eurasia.
Name Country Taxon Age in Ma Stage Latitude Longitude Reference
21 Çe¸
stepe, Kazan Basin Turkey Varanus sp. 5–5.2 Zanclean 40.3252 32.6894 Sen, Delfino & Kazanci (2017)
20 Süleymanli Turkey Varanus sp. 5.3–7.1 Zanclean-Messinian 37.9000 36.8333 Böhme & Ilg (2003)
19 Jradzor-3 (JZ-3) Armenia Varanus sp. 5.3–6 Messinian This study
18 Brisighella Cava Monticino Italy Varanus sp. 5.33–6 Messinian 44.2167 11.7667 Delfino (2002)
17 Polgárdi 5 Hungary Varanus sp. 5.33–6.2 Messinian 47.0500 18.0300 Venczel (2006)
16 Solnechnodolsk Russia Varanus sp. 5.8–6.4 Messinian Čerňanský, Syromyatnikova & Jablonski (2018)
15 Pollenzo section along
Tanaro River,
Verduno, Piedmont
Italy Varanus sp. 5.42–5.55 Messinian 44.6858 7.9314 Colombero et al. (2014)
14 El Arquillo 1 (ARQ1) Spain Varanus sp. 6.23 Messinian 40.4000 −1.1000 Ivanov et al. (2018)
13 Samos 1 Greece Varanus
marathonensis 6.9–7.2 Messinian 37.8000 26.9000 Villa et al. (2018)
12 Pikermi near Athens Greece Varanus
marathonensis 7.11–7.37 Messinian-Tortonian 38.0194 23.9917 Villa et al. (2018)
11 Kohfidisch Austria Varanus sp. 8.55–8.95 Tortonian 47.1667 16.3500 Tempfer (2005)
10 Kü¸
cük¸
cekmece Turkey Varanus sp. 8.6–9.4 Khersonian Tortonian 40.9833 28.7667 Vasilyan, Böhme & Prieto (2013)
9 Tetri Udabno Georgia Varanus sp. 7.6–9.6 Khersonian Tortonian This study
8 Cerro de los Batallones
(Torrejón de Velasco),
Madrid Basin
Spain Varanus
marathonensis 9–10 Tortonian 40.1794 −3.7246 Villa et al. (2018)
7 Ravin de la Pluie near
Nea Messimvria,
Axios Valley, 25 km
W Thessaloniki
Greece Varanus sp. 9.3 Tortonian 40.7530 22.7750 Georgalis et al. (2018)
6 Varnitza Moldova Varanus sp. 9.6–10.5 late Bessarabian Tortonian 46.8641 29.4692 Lungu & Rzebik-Kowalska (2011)
5 Kalfa Moldova Varanus sp. 10.5–11.6 middle Bessarabian Tortonian 46.9042 29.3753 Chkhikvadze & Lungu (1984)
4 Bushor 1 Moldova Varanus sp. 10.5–11.6 middle Bessarabian Tortonian 46.9225 28.2683 Lungu & Rzebik-Kowalska (2011)
3 Can Llobateres
(Valles Penedes Basin. Barcelona) Spain Varanus sp. 9.64–9.74 Tortonian 41.5333 −2.1333 Ivanov et al. (2018)
2 Otovaska 1 Moldova Varanus sp. 10.5–11.6 middle Bessarabian Tortonian Lungu & Rzebik-Kowalska (2011)
1 Petersbuch 18 Germany Varanus sp. 11.5–12.5 Tortonian 48.9779 11.1909 Böhme (2003)
Vasilyan and Bukhsianidze (2020), PeerJ, DOI 10.7717/peerj.8322 4/12
Table 2 Measurements of vertebrae and estimated body size of the studied specimens of Varanus sp. from Armenia and Georgia. Measure-
ments follow * Holmes et al. (2010) and ** Hocknull et al. (2009). The estimated body size corresponds to the snout-vent length.
Collection numbers Measurements (in mm) Estimated body
size (in mm) **
min.
centrum
length*
max.
centrum
length*
condylar
width*
precondylar
constriction*
DVL**
JRD-18/12 8 10.5 6.2 4.3 (69.3%) 8 290
GNM1 32-2013/1107-a1 – – – 6.2 – –
GNM1 32-2013/1107-a2 12.6 16.1 10.45 6.5 (62.2%) 13 470
GNM1 32-2013/1107-a3 – – 10.2 – – –
GNM132-2013/1107-b – – ∼9 – – –
GNM1 32-2013/1107-c1 – – – 7.4 – –
GNM1 32-2013/1107-c2 – – 10.3 – – –
GNM1 32-2013/1107-d1 – – – 6.6 – –
GNM1 32-2013/1107-d2 – – 10.5 – – –
GNM1 32-2013/1107-e – – 8.6 – – –
GNM1 32-2013/1107-f – – – 6 – –
Description
The vertebrae from both localities belong to small-sized individuals. The estimated snout-
vent length of the Armenian form (IGS JRD-18/13) is around 30 cm, whereas the Georgian
one (GNM1 32-2013/1107-a2) is nearly 50 cm (Table 2).
An anterior portion of the right dentary is preserved. It shows three tooth positions.
The dentary is slender and low. In labial view, the bone is flat and pierced by four small-
sized dorsoventrally compressed mental foramina, which are arranged horizontally. In
lingual view, the Meckelian groove is low and narrow. Below the third tooth, the groove
opens medially and at the anterior part of the preserved fragment (the first and second
tooth positions) the groove opens ventromedially. The symphyseal surface is oriented
medioposteriorly. The teeth are linguolabially compressed and incline posteriorly. The
first tooth measures two mm in height, the second four mm. The tooth base is broad
and composed of a system of parallel-oriented striae which are directed to the tip of the
tooth. Well-developed resorption pits are visible at the base of teeth, located between
parallel-oriented striae. The transition from the tooth base to the tooth crown is narrow.
The sharp distal and medial cutting edges of the tooth crown are serrated.
The studied vertebrae from both Jradzor and Tetri Udabno localities show the same
morphology. The vertebrae are procoelous, and all of them originate from the trunk
region. The vertebral centra are triangular in shape (anteriorly broad and posteriorly
narrow). The condyle and cotyle are dorsoventrally strongly compressed. The dorsal
margin of the cotyle projects over the ventral one. The surface of the condyle is smooth.
The precondylar constriction is strongly pronounced. The anterior opening of the neural
canal is round, whereas the posterior one has a flat ventral surface. In lateral view, the
neural arch projects posterodorsally. Its most anterior portion is flat and forms a triangular
surface in a depression. The dorsal surface of the neural arch possesses weakly- (Jradzor)
Vasilyan and Bukhsianidze (2020), PeerJ, DOI 10.7717/peerj.8322 5/12
Figure 2 Varanus sp. from Armenia and Georgia. (A–C) right dentary, IGS JRD-18/12, and (D–H) trunk vertebra, IGS JRD-18/13 from locality
Jradzor, horizon JZ-3, Armenia. (I–M) trunk vertebrae, GNM1 32-2013/1107-a - -f from locality Tetri Udabno, Georgia.
Full-size DOI: 10.7717/peerj.8322/fig-2
or well-pronounced (Tetri Udabno) striae. The neural arch possesses relatively high neural
crest. The pre- and postzygapophyses are bent laterodorsally.
An additional three bones with their partially-preserved diastemal and epiphyseal parts
have been found from Tetri Udabno. Due to the preservation of the material, these remains
cannot be referred to any bone. However, the fossil remains (vertebrae and long bones
fragments) of Varanus sp. from Tetri Udabno belong most probably to one individual,
because the bones are found together, have the same preservation, and the vertebrae are
partially articulated. However, the long bone fragments from the same spot cannot be
assigned with confidence to Varanus sp.
Vasilyan and Bukhsianidze (2020), PeerJ, DOI 10.7717/peerj.8322 6/12
DISCUSSION
Identification and comparison
The described fossil material shows characteristic features of the genus Varanus: (1)
the presence of a system of well-pronounced and parallel-oriented laminae, as well as
well-developed resorption pits at the base of the teeth (Kearney & Rieppel, 2006;Ivanov et
al., 2018); (2) the vertebral centrum possesses a well-pronounced precondylar constriction
(Smith, Bhullar & Holroyd, 2008;Conrad et al., 2011;Delfino et al., 2013); (3) the lateral
and dorsal surfaces of the neural arch of the vertebrae display distinct and generally
discontinuous striae (Smith, Bhullar & Holroyd, 2008).
Specific assignment of the studied material is impossible due to the lack of diagnostic
characters and further skeletal elements relevant for identification. However, several
differences from the already known Neogene forms of Europe can be mentioned. After
the latest comprehensive revision of the European Neogene monitor lizard record, only
two fossil species of the genus Varanus (V. mokrensis and V. marathonensis) are identified
in Eurasia (Ivanov et al., 2018). At least four additional middle to late Miocene species
have been described from the Eastern Paratethys area (Lungu, Zerova & Chkhikvadze,
1983;Zerova & Chkhikvadze, 1986) based on only isolated vertebrae. Unfortunately, all
material is poorly documented and the taxonomic assignment needs a critical revision
(Villa & Delfino, 2018). Thus, this record cannot be directly compared with Armenian and
Georgian material. Ivanov et al. (2018) used the dimensions of the trunk vertebrae (the ratio
of the condylar width to the precondylar constriction in %) to distinguish different species.
Our studied material shows the smallest values of this ratio (Table 2, 69.3% in Jradzor and
62.2% in Tetri Udabno) vs. 81% in V. mokrensis, and 75–78% in V. marathonesis (Ivanov
et al., 2018). Whether this difference could have a diagnostic significance to distinguish
species, i.e., to assign the Southern Caucasian Varanus sp. to a separate species, needs to be
tested further.
Taking into account the sizes of the bones, Varanus sp. from the Jradzor locality,
Armenia could represent a subadult form. The characters such as tooth serration and
degree of development of the striae on the vertebrae could be useful for the evaluation
of the ontogenetic stage. However, as it has been shown (Smith, Bhullar & Holroyd, 2008;
Hocknull et al., 2009), these characters have high intra- and interspecific variabilities, and
it is rather difficult to use them.
It is interesting to note that most of the Asiatic varanids have developed trenchant
and posteriorly directed teeth with serrated cutting edges (Ivanov et al., 2018) (similar
to Armenian form). In addition to this, the most western present-day distribution of
the genus Varanus is found in Iran (Anderson, 1999) and some parts of the Middle East
(Pianka, King & King, 2004). Interestingly, here, it is known by two small-sized species
Varanus bengalensis (SVL<750 mm) (Anderson, 1999) and Varanus griseus (SVL<860 mm)
(Pianka, King & King, 2004), which, unfortunately, we lack for comparison.
Vasilyan and Bukhsianidze (2020), PeerJ, DOI 10.7717/peerj.8322 7/12
CONCLUSIONS
Palaeobiogeographic and palaeoclimatic considerations
During the late Miocene, the genus Varanus was a common element of herpetofaunal
assemblages in the west of the Eastern Paratethys region (Fig. 1,Table 1). Recent studies (e.g.,
Čerňanský, Syromyatnikova & Jablonski, 2018) and our finds strongly suggest their larger
distribution covering regions west from the Black Sea. Monitor lizards are ectothermic and
their palaeogeographic distribution depends largely on suitable climatic conditions. So,
as suggested by Böhme (2003), the genus is characterized by the following climatic space:
mean annual temperature 14.8–28.1 ◦C, mean warm month temperature of 13.9–26.1 ◦C,
and mean cold month temperature of −3.9–19.4 ◦C. Comparable climatic conditions
can be also expected in Jradzor and Tetri Udabno. During the late Miocene, prominent
climatic changes have been documented both at the regional (Feurdean & Vasiliev, 2019)
and global scale (Herbert et al., 2016). Undoubtedly, they shaped also the spatial and
temporal distribution of all ectothermic vertebrates. Nevertheless, the herein documented
new finds are the first records of monitor lizards in the region. More systematic fieldwork
and studies are necessary to understand their fossil record in the region.
ACKNOWLEDGEMENTS
We would like to thank Hayk Hovakimyan (Institute of Geological Sciences of the Armenian
Academy of Sciences, Yerevan, Armenia) and Ilona Stepanyan (Zoological Institute of the
Armenian Academy of Sciences, Yerevan, Armenia) for assistance in the field for collecting
the material from the Jradzor locality. We express special thanks to Lilit Sahakyan (Institute
of Geological Sciences of the Armenian Academy of Sciences, Yerevan, Armenia) for
assistance with administrative issues related to the field activities in Armenia. Patrik
Röschli assisted in the preparation of illustrations. We are grateful to Andrea Villa and an
anonymous reviewer for criticism and constructive reviews, as well as the handling editor
of this paper Andrew Farke for critical reading and linguistic review of this paper.
ADDITIONAL INFORMATION AND DECLARATIONS
Funding
This project was supported by the Shota Rustaveli Georgian Science Foundation, project
#217626 for Maia Bukhsianidze. The funders had no role in study design, data collection
and analysis, decision to publish, or preparation of the manuscript.
Grant Disclosures
The following grant information was disclosed by the authors:
Shota Rustaveli Georgian Science Foundation: #217626.
Competing Interests
The authors declare there are no competing interests.
Vasilyan and Bukhsianidze (2020), PeerJ, DOI 10.7717/peerj.8322 8/12
Author Contributions
•Davit Vasilyan conceived and designed the experiments, performed the experiments,
analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or
tables, authored or reviewed drafts of the paper, approved the final draft.
•Maia Bukhsianidze performed the experiments, analyzed the data, contributed
reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the
final draft.
Field Study Permissions
The following information was supplied relating to field study approvals (i.e., approving
body and any reference numbers):
The Institute of Geological Sciences approved the field work in Armenia.
The fieldwork in Georgia has been provided by the leading national institution - Georgian
National Museum.
Data Availability
The following information was supplied regarding data availability:
One right dentary (IGS JRD-18/12) and one trunk vertebra (IGS JRD-18/13), Jradzor
locality, horizon JZ-3, late Miocene, late Messinian, late MN13, Armenia.
Ten trunk vertebrae (GNM 32-2013/1107-a —f) and three limb bones (GNM 32-
2013/1107-g —i), locality Tetri Udabnos Seri, late Miocene, late Tortonian, Khersonian,
Georgia.
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