Vjushkovia – at the base of the Rauisuchia and the Archosauria
Vjushkovia is considered an Early-Middle Triassic erythrosuchid and indeed it could be considered as such since it is a descendant of the erythrosuchids. In the large reptile tree Vjushkovia was more derived than erythrosuchids and Euparkeria, Riojasuchus and Ornithosuchus. It nested at the base of the Rauisuchia and this clade nested at the base of the Yarasuchus + Qianosuchus + Ticinosuchus and the highly armored Aetosauria. And these clades were basal to the Archosauria (crocs + dinos).
Figure 1. Vjushkovia. This largely overlooked taxon is an erythrosuchid descendant that was ancestral to the Rauisuchia, the Aetosauria and the Archosauria. Click to learn more.
Other than here, Vjushkovia has not gotten a lot of press. And that’s too bad considering its importance at the “crossroads” of the Archosauria and Rauisuchia. Wiki reports, “The ankle does not have the large calcaneal “heel” that characterizes those two clades [ornithosuchids and rauisuchids) and marks the origin of the Archosauria.” Not sure why they said this about the archosaur ankle, because the basal archosaur ankle is not enlarged. It does become enlarged by convergence in poposaur dinosaurs and in derived crocs, like Protosuchus.
All descendants of Vjushkovia have a longer pubis and ischium, (check out Decuriasuchus, for instance) so there is a likely transitional taxon that looks like Vjushkovia, but with a deeper pelvis that we haven’t found yet. This morphology also indicates a more erect set of hind limbs (again, like all of its descendant taxa). So at this point we’re taking the first tentative steps in the gradual accumulation of bipedal traits in derived taxa like basal crocs and basal dinosaurs.
I’d like to know more about Vjushkovia if any more data is available.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
References
Huene F von 1960. Ein grosser Pseudosuchier aus der Orenurger Trias. Palaeontographica Abteilung A 114:105-111
2012-12-03 20:02:24
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