''Telmasaurus'' is an extinct genus of

varanoid Varanoidea is a superfamily of lizards, including the well-known family Varanidae (the monitors and goannas). Also included in the Varanoidea are the Lanthanotidae (earless monitor lizards), and the extinct Palaeovaranidae. Throughout their lo ...

lizard from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million ...

. Fossils have been found from the Djadokha and

Barun Goyot Formation The Barun Goyot Formation (also known as Baruungoyot Formation or West Goyot Formation) is a geological formation dating to the Late Cretaceous Period. It is located within and is widely represented in the Gobi Desert Basin, in the Ömnögovi Pr ...

s that date between the early and middle

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

stage from approximately 80 to 75 million years ago. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

''Telmasaurus grangeri'' was named in 1943.

Description

''Telmasaurus grangeri'' was named in 1943 and is now known from several fossils. Only two skulls are known, and the snout region is missing from both. Based on the size of these skulls, ''Telmasaurus'' was larger than other Cretaceous varanoid lizards, approaching the size of modern

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 rec ...

s. Its skull is flatter than most other varanoids. The fusion of two bones in the skull called frontals links ''Telmasaurus'' with other early varanids like '' Paravaranus''. The

lacrimal bone The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of ...

of ''Telmasaurus'' has a single hole in it, as do those of other early varanoids. The vertebrae of ''Telmasaurus'' are also known, and the way they attach to each other is very different from the way those of modern monitor lizards do. A small crest running between the eye sockets is a distinguishing feature of the genus.

Classification

''Telmasaurus'' was first classified in the family

Varanidae The Varanidae are a family of lizards in the superfamily Varanoidea within the Anguimorpha group. The family, a group of carnivorous and frugivorous lizards, includes the living genus '' Varanus'' and a number of extinct genera more closely rel ...

, making it a close relative of living monitor lizards. In a 1998 phylogenetic analysis, ''Telmasaurus'' was placed in a more basal position within Varanoidea. Under this placement, it was an intermediate form between helodermatids and the group containing monitor lizards and snakes. Below is a cladogram from the 1998 anaylis: In a 2008 analysis, the basal positioning of ''Telmasaurus'' remained well supported, but it was grouped with another varanoid called '' Saniwides''. ''Saniwides'' was once classified in Varanidae as a close relative of living monitor lizards. Other Cretaceous varanids like ''

Cherminotus ''Cherminotus'' is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, ''Cherminotus longifrons'', was named in 1984. Description and history ''Cherminotus longifrons'' was first described i ...

'' and ''

Aiolosaurus ''Aiolosaurus'' is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, ''Aiolosaurus oriens'', was named in 2000 from Ukhaa Tolgod, a rich fossil site in the Campanian-age Djadochta Formati ...

'' are similar in appearance to ''Telmasaurus'', but ''Telmasaurus'' is a more primitive member of Varanoidea. Below is a cladogram from the 2008 analysis:

References

{{Taxonbar, from=Q7697730 Late Cretaceous lepidosaurs of Asia Monitor lizards Lizard genera Prehistoric reptile genera Taxa named by Charles W. Gilmore Fossil taxa described in 1943