#itasuchidae

[arminreindl]

Large caimans, seacow predation and a new pepesuchine

What a week we just had when it comes to fossil crocodile news. Not one, not two, but three whole publications dropped this last week, each noteworthy in its own way.

The first of these was "New taxa of giant caimans from the southernmost hyperdiverse wetlands of the South American late Miocene", which coined two new genera of caiman from the Argentinian Ituzaingó Formation.

Tho the names are new, both are far from unknown. The first of these is Paranacaiman bravardi, which was described based on a fossil traditionally associated with Caiman lutescens (now deemd a nomen dubium). The second is Paranasuchus gasparinae, which was already described in 2013 under the name Caiman gasparinae.

I will say that I find the names to be a little poorly chosen. On its own either one works, but together they are very similar and feel like they might cause some confusion down the line, at least in science communication.

But that's just my own opinion. Regardless of nomenclature, they are interesting. I am currently working on reconstructing Paranasuchus, but I did wrap up Paranacaiman with a simple reconstruction of the skull and a quick scaling, revealing it to have potentially been just shy of five meters in length.

Barely a day later we got hit with more Miocene croc news, specifically a short note on crocodilian feeding traces being identified on the fossils of the dugong Culebratherium from Venezuela. The animal has bitemarks all over its body, but highlighted are those centered around the skull. In addition to simple punctures, some bitemarks appear to showcase dragging and slashing, possibly associated with the well known deathroll performed my crocs. Alltogether, this could hint at the fact that one of the large crocodilians of the Agua Clara Formation might have grasped the seacow by its snout to drown it before tearing into it. Given that the fossil locality is fairly new and the fact that they are nothing but bite marks, we do not know what crocodilian was responsible, tho the paper suggests a small to medium sized caiman. Feeding traces also show that tiger sharks got involved at some point, which mirrors fossil evidence from the Austrian Paratethys.

Artwork of the possible predation event by Jaime Bran

And the final croc paper of last week takes us back quite a bit further, all the way back to the Cretaceous. Epoidesuchus tavaresae is a new species and genus of pepesuchine peirosaurid from the Adamantina Formation of Brazil, famous for its diversity of notosuchians (and apparent lack of modern crocs sans one exception).

Now for those unfamiliar, Pepesuchinae is a subfamily of Peirosaurids, best recognized by having slender, very crocodilian-like jaws that may indicate more semi-aquatic habits, as opposed to the more terrestrial and almost pig-like peirosaurines such as Uberabasuchus.

I should mention that theres some debate around the nomenclature. The paper follows the idea that Pepesuchinae is a subfamily of Peirosauridae, but a more recent paper (which at least two of the authors including the lead worked on) has Peirosaurinae and Pepesuchinae both as fully-fledged families, with the latter going by the name Itasuchidae (which is the older name). I should further mention that the nomenclature paper coined the clade Peirosauria to contain both these families and Mahajangasuchidae.

Anyways, tho fragmentary, we know that Epoidesuchus had the same narrow jaws as many other pepesuchines/itasuchids and was likely semi-aquatic. Given that neosuchians are rarer in South America, it seems very possible that their nische was largely filled by these specialised notosuchians, which strayed from the usual terrestrial habits of their group. In fact, tho many different notosuchians are known from the Bauru Group, the only neosuchian recovered so far is the recently named Titanochampsa.

Below the gorgeous press art by Guilherme Gehr

All three papers in order

New taxa of giant caimans from the southernmost hyperdiverse wetlands of the South American late Miocene: Journal of Systematic Palaeontology: Vol 22 , No 1 - Get Access (tandfonline.com)

Full article: Trophic interactions of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela (tandfonline.com)

A new Peirosauridae (Crocodyliformes, Notosuchia) from the Adamantina Formation (Bauru Group, Late Cretaceous), with a revised phylogenetic analysis of Sebecia - Ruiz - The Anatomical Record - Wiley Online Library