''Sineoamphisbaena'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of squamate of uncertain phylogenetic placement. Its fossils have been found in Late Cretaceous deposits in Inner Mongolia, China. It contains a single species, ''Sineoamphisbaenia hexatabularis.''

Taxonomic affiliation

Wu ''et al.'' and Gao proposed and argued that ''Sineoamphisbaenia'' was the oldest known

amphisbaenia Amphisbaenia (called amphisbaenians or worm lizards) is a group of usually legless squamates, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. As ...

n; this, however, was challenged by other authors, such as Kearney and Conrad, who instead assigned ''Sineoamphisbaena'' to the group of squamates variously known as Macrocephalosauridae, Polyglyphanodontidae or

Polyglyphanodontia Polyglyphanodontia, also known as the Borioteiioidea, is an extinct clade of lizards from the Cretaceous that includes around a dozen genera. Polyglyphanodontians were the dominant group of lizards in North America and Asia during the Late Cretac ...

. A large-scale study of fossil and living squamates published by Gauthier ''et al.'' in 2012 did not find evidence for a particularly close relationship between amphisbaenians and ''Sineoamphisbaena''; in their primary analysis ''Sineoamphisbaena'' was found to be the sister taxon of the clade containing snakes, amphisbaenians, the family Dibamidae and the

American legless lizard The family Anniellidae, known as American legless lizards, contains six species in a single genus ''Anniella'': ''A. pulchra'', the California legless lizard, the rare ''A. geronimensis'', Baja California legless lizard, and four more discovered i ...

. The primary analysis of Gauthier ''et al.'' did not support a close relationship between ''Sineoamphisbaena'' and polyglyphanodontians either; however, the authors noted that when all snake-like squamates and mosasaurs were removed from the analysis, and burrowing squamates were then added individually to it, ''Sineoamphisbaena'' grouped with polyglyphanodontians. Gauthier ''et al.'' considered it possible that ''Sineoamphisbaena'' was a burrowing polyglyphanodontian.

Sources

* ''World Encyclopedia of Dinosaurs & Prehistoric Creatures: The Ultimate Visual Reference To 1000 Dinosaurs And Prehistoric Creatures Of Land, Air And Sea ... And Cretaceous Eras (World Encyclopedia)'' by Dougal Dixon

References

Prehistoric squamates Prehistoric reptile genera Late Cretaceous lepidosaurs of Asia Fossils of Mongolia {{cretaceous-reptile-stub