What is Tasmaniosaurus?

Updated September 20, 2014 with a new reconstruction and nesting for this taxon.

Revised skull reconstruction of Tasmaniosaurus nesting at the base of the Erythrosuchia.

Revised skull reconstruction of Tasmaniosaurus nesting at the base of the Erythrosuchia.

Ezcurra 2014 considered the tiny Early Triassic archosauriform Tasmaniosaurus traissicus (Camp and Banks 1978) a tiny proterosuchid, following the original assessment.

Previous authors thought the maxilla was exposed in lateral view. If so, it has a maxillary fossa. Ezcurra thought the maxilla was exposed in medial view. Proterosuchids do not have a maxillary fossa. If the premaxilla was not downturned, Tasmaniosaurus is anything but a proterosuchid. If the maxilla is exposed in lateral view, Tasmaniosaurus is anything but a proterosuchid.

The caudal vertebrae are very long, longer than 3x their width, very un-proterosuchid like. Seven in a row have no neutrals spines.

The interclavicle of Tasmaniosaurus is T-shaped with a very long and slender posterior process. Among archosauriforms, only Euparkeria has a T-shaped interclavicle. Many are I-shaped.

The femur and tibia/fibula are short and robust, so no possible biped here and the Early Triassic is a little too early for bipeds.

Tasmaniosaurus is tiny. About the size of Youngina and Euparkeria, much smaller than any known proterosuchid or erythrosuchid.

In phylogenetic analysis (not updated online yet), Tasmaniosaurus nests at the base of the Erythrosuchidae, as a sister taxon to Fugusuchus + Revueltosaurus. So, another miniaturized taxon nests basal to a large clade.

References
Camp CL, Banks MR 1978. A proterosuchian reptile from the Early Triassic of Tasmania. Alcheringa 2: 143–158.
Ezcurra MD. 2014. The Osteology of the Basal Archosauromorph Tasmaniosaurus triassicus from the Lower Triassic of Tasmania, Australia. PLoS ONE 9(1):e86864. doi:10.1371/journal.pone.0086864

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