''Varanus darevskii'', also known as the Central Asian monitor, is an extinct

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recogn ...

from the Early

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Tajikistan Tajikistan (, ; tg, Тоҷикистон, Tojikiston; russian: Таджикистан, Tadzhikistan), officially the Republic of Tajikistan ( tg, Ҷумҳурии Тоҷикистон, Jumhurii Tojikiston), is a landlocked country in Centr ...

, known from a partial skull. ''V. darevskii'' might have been a close relative of, and perhaps ancestral to, the modern

desert monitor The desert monitor (''Varanus griseus'') is a species of monitor lizard of the order Squamata found living throughout North Africa and Central and South Asia. The desert monitor is carnivorous, feeding on a wide range of vertebrates and inverteb ...

(''V. griseus'').

Discovery and naming

''Varanus darevskii'' was described by the Russian palaeontologist

Irina Levshakova Irina Yuryevna Levshakova (née Kuznetsova; Russian: Ирина Юрьевна Левшакова; 6 May 1959 – 31 January 2016) was a Russian paleontologist, geologist, artist and musician. She is most famous for her deep involvement in the ...

in 1986, based on a partial skull in comparatively good condition from the

Early Pliocene Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early ...

found near the village of Sor in the

Sughd Region Sughd Province ( tg, Вилояти Суғд, Viloyati Sughd, Sogdia Region , fa, ولایت سغد) is one of the four administrative divisions and one of the three provinces ( tg, вилоятҳо, viloyatho , fa, ولایت) that make up ...

Tajikistan Tajikistan (, ; tg, Тоҷикистон, Tojikiston; russian: Таджикистан, Tadzhikistan), officially the Republic of Tajikistan ( tg, Ҷумҳурии Тоҷикистон, Jumhurii Tojikiston), is a landlocked country in Centr ...

. The skull preserved the snout in its entirety, alongside portions of the

skull roof The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparati ...

and

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sepa ...

. The species name ''darevskii'' honors the Russian zoologist and

herpetologist Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians (gymnophiona)) and rept ...

Ilya Darevsky Ilya Sergeyevich Darevsky (russian: Илья Сергеевич Даревский, 18 December 1924 – 8 August 2009) was a Soviet Russian zoologist-herpetologist and a corresponding member of the Russian Academy of Sciences. During his career ...

. Levshakova also gave the species a

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

, calling it the Central Asian monitor.

Description

The skull of ''V. darevskii'' is similar to the modern

(''V. griseus''), but differs by having a broader parietal region and a more pointed tip of the snout. Though the fossil is incompletely preserved, it is also possible that the

orbits In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

of ''V. darevskii'' were larger than those of ''V. griseus''. ''V. darevskii'' was slightly smaller than ''V. griseus'' (which usually grow to about one meter in length), but had bigger teeth.

Classification

Levshakova classified ''V. darevskii'' within the ''Varanus'' subgenus '' Psammosaurus'' (which also contains ''V. griseus'') on the basis of both anatomy and

zoogeography Zoogeography is the branch of the science of biogeography that is concerned with geographic distribution (present and past) of animal species. As a multifaceted field of study, zoogeography incorporates methods of molecular biology, genetics, mo ...

. She believed ''V. darevskii'' to be closely related, perhaps ancestral, to ''V. griseus''. Levshakova further placed the extinct species '' V. marathonensis'' in the same subgenus, arguing that it too was a close relative of ''V. darevskii''. A 2018 analysis found ''V. marathonensis'' to fall outside of such a clade with ''V. griseus'', instead being more closely related to eastern ''Varanus'' species such as '' V. flavescens'' and '' V. bengalensis''. According to the 2004 reference work ''Varanoid Lizards of the World'' by Eric R. Pianka, Dennis King and Ruth Allen King, Levshakova's classification of ''V. darevskii'' is sensible and it would not be surprising if ''V. griseus'' were a descendant of ''V. darevskii'', although no

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

studies have yet taken ''V. darevskii'' into account and confirmed it. A 2016 analysis recovered ''V. darevskii'' as belonging to the subgenus '' Polydaedalus'', which includes modern species such as the

Nile monitor The Nile monitor (''Varanus niloticus'') is a large member of the monitor family (Varanidae) found throughout most of Sub-Saharan Africa and along the Nile, with invasive populations in North America. The population in West African forests and sa ...

(''V. niloticus''),

rock monitor The rock monitor (''Varanus albigularis'') is a species of monitor lizard in the family Varanidae. The species is endemic to Central, East, and southern Africa. It is the second-longest lizard found on the continent, and the heaviest-bodied; lo ...

(''V. albigularis'') and

savannah monitor The savannah monitor (''Varanus exanthematicus'') is a medium-sized species of monitor lizard native to Africa. The species is known as Bosc's monitor in Europe, since French scientist Louis Bosc first described the species. It belongs to the su ...

(''V. exanthematicus''). If this classification is correct, ''V. darevskii'' would be the first known occurrence of ''Polydaedalus'' in western Asia.Conrad, Jack L.; Montanari, Shaena; Ast, Jennifer C.; Wasserman, Danielle S.; Norell, Mark (2016). "Fragmentary (and Complete) Fossils Help Reconstruct Monitor Lizard (Squamata, Varaniformes) Biology and Evolution".
Society of Vertebrate Paleontology October 2016: Abstracts of Papers 76th Annual Meeting
'

References

{{Taxonbar, from=Q19711009 daresvskii Fossil taxa described in 1986