Late Triassic Cryptovaranoides is a squamate again, but still not the oldest

According to Wikipedia – Cryptovaranoides,
“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.”

The first paper (Whiteside et al 2022) considered Cryptovaranoides
(NHMUK PV R36822) a crown squamate.

The second paper (Brownstein CD et al  2023) said it was an ‘archosauromorph’ close to Azendohsaurus and Trilophosaurus after µCT scans (see below).

The third and latest paper Whiteside et al 2024) reiterated its squamate affinities using µCT scans, but did not include the closest sister taxa recovered here in the LRT, nor did it include the oldest known crown-group squamate (see below).

This is an academic tempest in a teapot caused by taxon exclusion.

 BTW, Azendohsaurus and Trilophosaurus are lepidosaurs in the LRT.

Figure 1. Cryptovaranoides compared to the extant lizard, Acanthodactylus. Original DGS colors above. Standard DGS colors below-right. ” data-image-caption=”

Figure 1. Cryptovaranoides compared to the extant lizard, Acanthodactylus. Original DGS colors above. Standard DGS colors below-right.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.skull588.jpg?w=237″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.skull588.jpg?w=584″ class=”size-full wp-image-90096″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.skull588.jpg” alt=”Figure 1. Cryptovaranoides compared to the extant lizard, Acanthodactylus. Original DGS colors above. Standard DGS colors below-right.” width=”584″ height=”739″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.skull588.jpg?w=584&h=739 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.skull588.jpg?w=119&h=150 119w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.skull588.jpg?w=237&h=300 237w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.skull588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Cryptovaranoides compared to the extant lizard, Acanthodactylus. Original DGS colors above. Standard DGS colors below-right. Some changes to palate elements and the quadrate is flipped.

re: the latest study
Whiteside DI, Chambi-Trowell SAV and Benton MJ 2024 was hobbled by taxon exclusion (Fig 2). This results in some ‘closely related’ taxa (e.g. Pareiasuchus, Claudiosaurus and Coelurosauravus) sharing few to no character traits, sizes and niches.

Nobody seemed to notice or care. Always check your results for bogies like these.

In the Cryptovaranoides cladogram
(Fig 2) members of the LRT Lepidosauromorpha and Archosauromorpha are shuffled together creating odd pairings (noted above) as unrelated taxa are forced to nest together.

Figure 1. Cryptovaranoides compared to the extant lizard, Acanthodactylus. Original DGS colors above. Standard DGS colors below-right. ” data-image-caption=”

Figure 2. Cladogram from Whiteside et al 2024. Colors added here. This cladogam shuffles together unlike taxa from the LRT archosauromorpha and the LRT lepidosauromorpha. Compare to figure 3.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides-microlanius.cladogram588.jpg?w=123″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides-microlanius.cladogram588.jpg?w=418″ class=”size-full wp-image-90098″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides-microlanius.cladogram588.jpg” alt=”Figure 1. Cryptovaranoides compared to the extant lizard, Acanthodactylus. Original DGS colors above. Standard DGS colors below-right.” width=”584″ height=”1430″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides-microlanius.cladogram588.jpg?w=584&h=1430 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides-microlanius.cladogram588.jpg?w=61&h=150 61w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides-microlanius.cladogram588.jpg?w=123&h=300 123w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides-microlanius.cladogram588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Cladogram from Whiteside et al 2024. Borrowed from Simoes et al 2022. Colors added here. This cladogam shuffles together unlike taxa from the LRT archosauromorpha and the LRT lepidosauromorpha. Compare to figure 3.

A competing cladogram, the LRT,
minimizes taxon exclusion by including 2326 taxa and so does not have this problem. All sister taxa resemble one another demonstrating microevolutionary steps. The last common ancestor of all amniotes = reptiles is Silvanerpeton. (Omitted by all prior studies) The first dichotomy splits Lepidosauromorpha from Archosauromorpha following traditional definitions for both clades, now with an expanded list of members. The LRT recovered that tree topology in 2011.

Also not recognized by academics due to taxon excluion, the diapsid skull architecture appears twice by convergence in the larger study found online here. 

If you’re going to study paleontology at the university level, be prepared for out-of-date cladograms (Fig 2) that omit long lists of taxa with results that no one checks for logic and microevolution – and yet everyone borrows.

Figure 3. Subset of the LRT with the addition of Cryptovaranoides in the extant Acanthodactylus clade. Note the Early Permian oldest known squamate precedng Cryptovaranoides. ” data-image-caption=”

Figure 3. Subset of the LRT with the addition of Cryptovaranoides in the extant Acanthodactylus clade. Note the Early Permian oldest known squamate precedng Cryptovaranoides.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.cladogram588.jpg?w=158″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.cladogram588.jpg?w=540″ class=”size-full wp-image-90109″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.cladogram588.jpg” alt=”Figure 3. Subset of the LRT with the addition of Cryptovaranoides in the extant Acanthodactylus clade. Note the Early Permian oldest known squamate precedng Cryptovaranoides.” width=”584″ height=”1106″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.cladogram588.jpg?w=584&h=1106 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.cladogram588.jpg?w=79&h=150 79w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.cladogram588.jpg?w=158&h=300 158w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/11/cryptovaranoides.cladogram588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 3. Subset of the LRT with the addition of Cryptovaranoides in the extant Acanthodactylus clade. Note the Early Permian oldest known squamate precedng Cryptovaranoides was omitted from the Whiteside et al 2024 study.

What did Brownstein et al 2023 see in their µCT scans?
They wrote, “We robustly reject the crown squamate affinities of †Cryptovaranoides, and instead resolve †Cryptovaranoides as a potential member of the bird and crocodylian total clade, Archosauromorpha.”

(see below for more specific results)

“We tested the phylogenetic affinities of †C. microlanius [= Cryptovaranoides] and divergence times for the major groups of squamates using three radically different phylogenetic matrices (updated to include several recently published early lepidosaurs and early squamates) under various optimality criteria. We find no support for the placement of †C. microlanius within Anguimorpha or even crown Squamata, with a broader reptile dataset suggesting that it is in fact an archosauromorph reptile.”

(see below for more specific results)

“we included [Cryptovaranoides] in the largest available dataset to infer relationships among the major groups of reptiles [Simoes et al 2022], as it extensively samples early amniotes, the early radiation of the major groups of reptiles, and the two major reptile crown groups: lepidosauromorphs and archosauromorphs..

Borrowing cladograms is NEVER a good idea. That involves trust. Trust is not part of the scientific method. Borrowing is not part of the scientific method. Testing IS part of the scientific method.

That being said,
the Simoes et al 2022 cladogram (Fig 2) suffers from massive taxon exclusion relative to the LRT. Brownstein et al nested Cryptovaranoides basal to Azendohsaurus, Trilophosaurus and the Rhynchosauria, which they did not realize were all lepidosaurs in the LRT. Just add taxa to find this out for yourself. Their outgroup taxa for that clade were Protorosaurus and Prolacerta, two members of the Archosauromorpha. These two look like lepidosaur tanystropheids, but they are not (Peters 2007, the LRT).

Acanthodactylus (Fig 1) was omitted.

This is where adding taxa would help.

This is where side-by-side skull graphics to scale (Fig 1) would help.

By including so many taxa
in such a wide gamut, the LRT (subset Fig 3) minimizes taxon exclusion, a problem found to be present in all prior studies. Build your own LRT so you, too, will recognize short lists when you see them.

Publicity
Sclenceblog.com wrote, “A tiny fossil from Triassic-era rocks has reignited the debate about lizard evolution, with new analysis confirming it as the world’s oldest modern-type lizard – pushing back the origins of today’s lizards and snakes by 35 million years.”

“Among the most compelling evidence are the specimen’s pleurodont teeth – teeth attached to the inner surface of the jaw, a hallmark feature of modern lizards. The team also identified specific structures in the braincase and palate that are typical of squamates but absent in archosauromorphs (the group including crocodiles and dinosaurs).”

Eurekalert.org wrote, “The discovery shifts the origin of the whole lizard-snake group, called Squamata, back by 35 million years.

In the LRT Cryptovarranius (205 mya) is a derived member of the Squamata. An early Permian (290 mya) iguanid, not Ascendonanus nestleri, is the earliest known squamate in the LRT. Iguania is the most primitive clade within the Squamata. Thus Ascendonanus is 85 million years older than Cryptovaranoides.

Omitting taxa is one way to make the headlines. Not the best way.

Unfortunately this is not co-author Mike Benton’s first brush with omitting taxa. For an index of blogposts featuring Mike Benton’s work click here.

“In checking their original work, and the questions posed in the rival paper, the Bristol team explored all the data, including the original specimen as well as the X-ray scans that show the details hidden within the rock. “We had the marvellous images from those CT scans as well as further access to the fossil which enabled us to check all their suggestions,” said Dr Chambi-Trowell. “We found that most of the concerns raised were wrong.”

In this case, taxon exclusion was the real problem.

Happy Thanksgiving to my American readers.

References in chronological order
Whiteside DI, Chambi-Trowell SAV and Benton MJ 2022. A Triassic crown squamate. Science Advances. 8 (48): eabq8274.
Brownstein CD et al (5 co-authors) 2023. The affinities of the Late Triassic Cryptovaranoides and the age of crown squamates. Royal Society Open Science. 10 (10).
Whiteside DI, Chambi-Trowell SAV and Benton MJ 2024. Late Triassic †Cryptovaranoides microlanius is a squamate, not an archosauromorph. Royal Society Open Science. 11 (11). 231874.

Other references
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Simões TR, Kammerer CF, Caldwell MW, Pierce SE 2022 Successive climate crises in the deep past drove the early evolution and radiation of reptiles. Sci. Adv. 8, eabq1898. (doi:10.1126/sciadv.abq1898)
Spindler F, Werneburg R, Schneider JW, Luthardt L, Annacker V and Räler R 2018. First arboreal ‘pelycosaurs’ (Synapsida: Varanopidae) from the early Permian Chemnitz Fossil Lagerstätte, SE Germany, with a review of varanopid phylogeny. DOI: https://doi.org/10.1007/s12542-018-0405-9