Ford and Benson reexamine Orovenator

I have to wonder if workers
are gleaning this blog for taxa in need of study, taxa that were originally poorly nested. Probably just a coincidence that Ford and Benson 2017 took another look at Orovenator (early Permian), which was originally (Reisz et al. 2011) described as the earliest of the ‘Neodiapsida’ (archosaurs, lepidosaurs and turtles).

By contrast
in the large reptile tree (LRT, 1054 taxa) that clade is called ‘Reptilia’ and its earliest known member is Tulerpeton from the Latest Devonian. So ‘Neodiapsida’ is a junior synonym for Reptilia and needs to be ditched. Orovenator is something else.

Figure 1. Orovenator (holotype on right) along with the larger referred specimen (on left, and scaled down to the size of the holotype above right). Arrows point to mismatches.

Figure 1. Orovenator (holotype on right) along with the larger referred specimen (on left, and scaled down to the size of the holotype above right). Arrows point to mismatches.

The authors used two skulls
to recreate a more complete one, pretty much like I avoided three years ago (Fig. 1) because the referred specimen was not a good match. The LRT nests Orovenator with several of the taxa listed below as synapsid-grade pro-diapsids. In other words, they are derived from basal synapsids, like Vaughnictis, but are in the lineage of new archosaurmorph (non-lepidosaur) diapsids, like Eudibamus. This Prodiapsid clade/grade has not been recognized yet by other workers.

From their abstract
“Substantial similarity between early diapsids and varanopid synapsids has previously been noted: four taxa currently assigned to the Varanopidae were originally described as diapsids (Archaeovenator, HeleosaurusApsisaurus) or archosauromorphs (Mesenosaurus). However, our study suggests that these similarities are greater than previously appreciated, raising questions about deep phylogenetic divergences within amniotes.”

And here’s the kicker, again from their abstract
“Application of the new data on Orovenator into an existing phylogenetic matrix intended to discriminate between varanopids and diapsids resulted in an unresolved consensus. This has prompted work on a novel phylogeny, with greater taxonomic scope, to provide a working hypothesis for the interrelationships of Permo-Carboniferous amniotes.”

Yay!
We love adding taxa, increasing the taxonomic scope (gamut) and the novel phylogenies that result. If Ford and Benson recover Prodiapsida from the Synapsida, remember, you heard it here first.

References
Ford DP and Benson RBJ 2017. A re-examination of Orovenator mayorum using µCT data, and its consequences for early amniote phylogeny. SVPCA-SPPC Birmingham abstracts. September 12-15, 2017.
Reisz RR, Modesto SP and Scot DMT 2011. A new Early Permian reptile and its significance in early diapsid evolution. Proceedings of the Royal Society, London B

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.