Among the most interesting of recently discovered fossil lizards are the borioteiioids… yeah, a lot of vowels there… a group of robust-skulled, heterodont, teiid-like lizards mostly associated with the Cretaceous of Asia and North America. Here’s a very brief intro on this group, extracted and modified from a longer piece of text that has an… interesting backstory. Some borioteiioid taxa are extremely specialized and possess a suite of unusual features absolutely not typical for lizards: Tianyusaurus from the Upper Cretaceous Qiupa Formation of Henan, China possesses a complete lower temporal bar, fixed quadrate, and enlarged maxillary caniniforms that have been interpreted as fruit-penetrating structures (Lü et al. 2008; Mo et al. 2010).

Polyglyphanodon sternbergi, a borioteiioid from the Maastrichtian of North America. This skeleton is on display at the American Museum of Natural History, New York, and is preserved lying on its back. Credit: Diderot Wikimedia 

Until recently, borioteiioids were mostly interpreted as part of Teiidae, the group that includes whiptails, racerunners and tegus (e.g., Estes 1983; Gao & Norell 2000), or as members of the specific teiid clades Tupinambini and Teiini (Estes 1969). More recently, borioteiioids have been excluded from Teiioidea – the clade that includes teiids as well as the closely related spectacled lizards or microteiids (Gymnophthalmidae) – and regarded as their sister-group (Nydam et al. 2007). Teiids are great – I totally have to write about them here some time soon.

Wow, teiids are great. At top: Argentine black and white tegu (Salvator merianae). Below: Northern caiman lizard (Dracaena guianensis). Credit: Darren Naish

Anyway… a major morphological analysis that included representatives of most squamate groups (Conrad 2008) found borioteiioids (termed Polyglyphanodontidae in the study concerned) to be nested within Lacertiformes and Teiioidea, and to have a sister-group relationship with teiids, the two forming a clade termed Macroteiida. Wiens et al. (2010) and Mo et al. (2010), similarly, supported a close affinity of borioteiioids with extant teiids and gymnophthalmids.

A montage of borioteiioid skulls, to scale. A. Tianyusaurus zhengi. B. Tuberocephalosaurus pompabilis. C. Darchansaurus estesi. D. Polyglyphanodon sternbegi. E. Gilmoreteius. Credit: Darren Naish

A rather heterodox idea was published by Gauthier et al. (2012): they argued that borioteiioids (termed by them Polyglyphanodontia) lack characters of the jugal, ectopterygoid and mandible universally present in the majority of lizards, and are outside of crown-Squamata and only convergently similar to teiioids. This hypothesis was also supported by Longrich et al. (2012). It’s an interesting proposal that challenges the familiar and traditional view on these animals. One consequence of this proposal is that the borioteiioid lineage must extend back to the Upper Jurassic at a minimum.

Life reconstruction of the Asian borioteiioid Gilmoreteius. Credit: Darren Naish

There’s a lot more to say about borioteiioids: the group is diverse, and includes several sub-groups… there are the polyglyphanodontids (which, according to Conrad, 2008, includes the gilmoreteiids or ‘macrocephalosaurs’), the chamopsiids and the tuberocephalosaurines. I aim to say more about them when time allows.

At least some of the content here was created for the in-prep Tet Zoo Big Book project.. The Vertebrate Fossil Record. More information on that project here. Thanks so much to those who provide support.

For a few of many previous Tet Zoo articles on lizards, see...

 

 

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Conrad, J. L. 2008. Phylogeny and systematics of Squamata (Reptilia) based on morphology. Bulletin of the American Museum of Natural History 310, 1-182.

Estes, R. 1969. Relationships of two Cretaceous lizards (Sauria, Teiidae). Breviora 317, 1-8.

Estes, R. 1983. Sauria terrestria, Amphisbaenia. New York: Gustav Fischer Verlag.

Gao, K.-Q. & Norell, M. A. 2000. Taxonomic composition and systematics of Late Cretaceous lizard assemblages from Ukhaa Tolgod and adjacent localities, Mongolian Gobi Desert. Bulletin of the American Museum of Natural History 249, 1-118.

Gauthier, J. A., Kearney, M., Maisano, J. A., Rieppel, O. & Behlke, D. B. 2012. Assembling the squamate tree of life: perspectives from the phenotype and the fossil record. Bulletin of the Peabody Museum of Natural History 53, 3-308.

Longrich, N. R., Bhullar, B. A. S. & Gauthier, J. A. 2012. Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences, USA 109, 21396-21401.

Lü, J.-C., Ji, S.-A., Dong, Z.-M. & Wu X.-C. 2008. An Upper Cretaceous lizard with a lower temporal arcade. Naturwissenschaften 95, 663-669.

Mo, J.-Y., Xu, X. & Evans, S. E. 2010. The evolution of the lepidosaurian lower temporal bar: new perspectives from the Late Cretaceous of South China. Proceedings of the Royal Society B: Biological Sciences 277, 331-336.

Nydam, R. L., Eaton, J. G. & Sankey, J. 2007. New taxa of transversely-toothed lizards (Squamata: Scincomorpha) and new information on the evolutionary history of “teiids”. Journal of Paleontology 81, 538-549.

Wiens, J. J., Kuczynski, C. A., Townsend, T., Reeder, T. W., Mulcahy, D. G. & Sites, J. W. 2010. Combining phylogenomics and fossils in higher-level squamate reptile phylogeny: molecular data change the placement of fossil taxa. Systematic Biology 59, 674-688.