Purbicella, a basal scleroglossan from the Purbeck Limestone

Figure 1. Purbicella in situ (palatal view) and traced using DGS, then reconstructed using those tracings. Gray areas are unknown. If you think this looks like a generalized, plesiomorphic scleroglossan, you're right! Here colorizing the bones helps identify sutures and paired elements. That's a right pterygoid covering much of the paired frontals. The teeth are blunt.

Figure 1. Purbicella in situ (palatal view) and traced using DGS, then reconstructed using those tracings. Gray areas are unknown. If you think this looks like a generalized, plesiomorphic scleroglossan, you’re right! Here colorizing the bones helps identify sutures and paired elements. That’s a right pterygoid covering much of the paired frontals. The teeth are blunt.

A few years ago
a rather complete lizard skull (BGS GSb581) was described (Evans et al. 2012) from the Purbeck Limestone (Late Jurassic to Early Cretaceous) of England. It was originally excavated more than a century ago and assigned to the genus, Paramacellodus. Evans et al. renamed it Purbicella. Their cladistic analysis nested Purbicella with Lacertoidea: (Lacertidae (including Acanthodactylus), Teiidae (including Tupinambus), Gymnophthalmidae (including Gymnophthalmus), and the burrowing Amphisbaenia (including Amphisbaena)), not Paramacellodus, which nested with skinks. Evans et al. based their nesting on a partial data matrix of Conrad (2008).

The large reptile tree nested Purbicella between Acanthodactylus and Liushusaurus. The large reptile tree recovered the above listed ‘lacertoid’ taxa as members of a paraphyletic clade, some preceding Purbicella in various clades and others succeeding it.

While Purbicella is Late Jurassic/Early Cretaceous, it must have had its origins much earlier, in the Late Carboniferous, because a descendant taxon, the TA1045 specimen, is Early Permian.

References
Conrad JL 2008. Phylogeny and systematics of Squamata (Reptilia) based on  morphology. Bulletin of the American Museum of Natural History 310:1–182.
Evans SE, Jones MEH and Matsumto R 2012. A new lizard skull from the Purbeck Limestone Group (Lower Cretaceous) of England. Bull. Soc. géol. France, 2012, t. 183(6):517-524.

 

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