SVP 2018: New enigmatic Middle Triassic ‘archosauriform’

Sues, Schoch, Irmis and Desojo 2018
discuss an odd new Middle Triassic ‘archosauriform’ that lacked dermal armor and had short 4.3cm femora.

Figure 1. Vancleavea is a thalattosaur with 3D preservation.

Figure 1. Vancleavea is a thalattosaur with 3D preservation.

They say it most closely resembles Vancleavea,
but Vancleavea is a thalattosaur in the LRT. Other thalattosaurs do not have dermal armor.

“A new archosauriform reptile from the Middle Triassic (Ladinian) Erfurt Formation of
Baden-Württemberg (Germany) differs from all other known non-archosaurian
archosauriforms in the structure of its dentition. The premaxilla holds five teeth with slightly recurved conical crowns. The maxilla has at least 11 markedly heterodont teeth. The mesial and distal carinae of the labiolingually flattened maxillary and dentary tooth crowns bear large serrations oriented at a steep angle to the apicobasal axis of the crown. All teeth have thecodont implantation.”

Figure 3. Subset of the LRT nesting Wachtlerosaurus with Thalattosaurus.

Figure 2. Subset of the LRT focusing on thalattosaurs.

Archosauriforms (IF the new taxon is one!) with more than four teeth in the premaxilla:

  1. Erythrosuchidae
  2. Stagonolepis
  3. Higher Crocodylomorpha
  4. Most Pararachosauriformes
  5. Basal, but not basalmost Ornithischia
  6. Several theropod clades

Only crocs have relatively short femora in this list. So do thalattosaurs.

Most Enaliosauria
have more than four teeth in the premaxilla. Thallatosaurs are enaliosaurs. At present there is too little data to make a decent ID. It is a shame that some of the top names in paleontology (the abstract authors) have not tested the nesting of Vancleavea with thalattosaurs in the LRT. I love enigmas! Should be interesting when the paper comes out.

References
Sues H-D, Schoch RR, Irmis R, Desojo JB 2018. A new archosauriform reptile from the Middle Triassic (Ladinian) of Germany documents greater trophic diversity among early archosauriformes. SVP abstracts.

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