Cryptovaranoides

Cryptovaranoides Temporal range: 202  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓ Late Triassic (Rhaetian)
Reconstruction of skull (top) and life restoration (bottom) as a squamate
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Genus:	† Cryptovaranoides Whiteside, Chambi-Trowell & Benton, 2022
Species:	†C. microlanius
Binomial name
†Cryptovaranoides microlanius Whiteside, Chambi-Trowell & Benton, 2022

Cryptovaranoides ("hidden lizard-like animal") is an extinct genus of reptile from the Late Triassic Magnesian Conglomerate of England. It contains a single species, Cryptovaranoides microlanius. ^[1]

Discovery and naming

It is represented by a holotype partial skeleton as well as referred isolated bones from Rhaetian-aged fissure fill-deposits in Slickstones Quarry, near Tortworth, Gloucestershire preserved alongside the common fossil rhynchocephalian Clevosaurus . The type specimen had been collected in 1953, but was only described as a distinct taxon in 2022. ^[1]

Classification

When first described, Cryptovaranoides was interpreted as a crown group squamate belonging to the clade Anguimorpha, based on features of the skull architecture, braincase, dentition and postcranium. Since fossils of crown-squamates otherwise are known only from the Middle Jurassic onwards, Cryptovaranoides would push back the estimated origin of modern squamates by 35 million years, implying that the radiation of modern squamate lineages occurred much earlier than previously assumed. ^{[1] [2] [3]} A 2023 study by Brownstein and colleagues reanalysed the type material, and rejected the hypothesis that Cryptovaranoides was a crown-squamate. In their unconstrained phylogenetic analysis, Cryptovaranoides was instead placed within Archosauromorpha as a relative of Allokotosauria. Even when Cryptovaranoides was constrained as a member of Squamata, it was recovered well outside the crown group. ^[4] However, the original describers of Cryptovaranoides maintained their original conclusion that this taxon represents a squamate. ^[5] The results of this paper were contested in a peer-reviewed preprint by Caldwell and colleagues in 2025, who noted methodological errors in the previous paper and concluded that Cryptovaranoides can not be regarded as a squamate. The researchers reinforced previous work identifying similarities to non-squamate neodiapsid reptiles, especially archosauromorphs such as Prolacerta , Macronemus , and Malerisaurus . ^[6]

References

1. Whiteside, D. I.; Chambi-Trowell, S. A. V.; Benton, M. J. (2022). "A Triassic crown squamate". Science Advances. 8 (48): eabq8274. Bibcode:2022SciA....8.8274W. doi:10.1126/sciadv.abq8274. hdl: 1983/a3c7a019-cfe6-4eb3-9ac0-d50c61c5319e . ISSN   2375-2548. PMC   10936055 . PMID   36459546.
2. Bristol, University of. "December: Lizard discovery | News and features | University of Bristol". www.bristol.ac.uk. Retrieved 2022-12-24.
3. "Gloucestershire fossil suggests modern lizards could have Triassic origins". www.nhm.ac.uk. Retrieved 2022-12-24.
4. Brownstein, C. D.; Simões, T. R.; Caldwell, M. W.; Lee, M. S. Y.; Meyer, D. L.; Scarpetta, S. G. (2023). "The affinities of the Late Triassic Cryptovaranoides and the age of crown squamates". Royal Society Open Science. 10 (10). doi:10.1098/rsos.230968. PMC   10565374 . PMID   37830017.
5. Whiteside, D. I.; Chambi-Trowell, S. A. V.; Benton, M. J. (2024). "Late Triassic †Cryptovaranoides microlanius is a squamate, not an archosauromorph". Royal Society Open Science. 11 (11). 231874. Bibcode:2024RSOS...1131874W. doi: 10.1098/rsos.231874 . PMC   11597406 . PMID   39606587.
6. Caldwell, Michael W.; Brownstein, Chase D.; Meyer, Dalton L.; Scarpeta, Simon G.; Lee, Michael S. Y.; Simões, Tiago R. "Cryptovaranoides is not a squamate". eLife (reviewed preprint). doi: 10.7554/eLife.107021.1 .