The droopy snout of Doswellia

UPDATED
on April 2, 2014 with new data on the pmx/mx suture and pmx ascending process.

Earlier, we looked at that odd archosauriform, Doswellia (Late Triassic, Weems 1980, Dilkes and Sues 2009, Heckert et al. 2012). It was originally considered a sister to Proterochampsidae, which is very close. The large reptile tree nested it as a basal, but not very plesiomorphic, choristodere, derived from a sister to Youngina BPI 2871 (Fig.1 ) and otherwise close to ChampsosaurusSimoedosaurus and Diandongosuchus.

Figure 1. The sister to Doswellia, the BPI2871 specimen of Youngina.

Figure 1. The sister to Doswellia, the BPI2871 specimen of Youngina.

Earlier I accepted the straight mandible reconstruction of Weems (1980) and Heckert et al. (figure 6, 2012).

However, the mandible illustrated alone in Dilkes and Sues (2009) is ventrally concave. Putting that into a reconstruction (Fig. 2) also matches the referred broken rostrum of Heckert et al. (2012).

The Droopy Snout
Convergent with Proterosuchus (Fig. 3), Doswellia had a droopy snout that started to droop at mix maxilla, instead of a the pmx/mx suture.

 

Figure 2. Click to enlarge. Doswellia reconstructed from bone pieces. The postfrontal and postorbital are fused but colored separately. A tiny lateral temporal fenestra remains. The larger specimen may have had a stronger curve in the rostrum.

Figure 2. Click to enlarge. Doswellia reconstructed from bone pieces. The postfrontal and postorbital are fused but colored separately. A tiny lateral temporal fenestra remains. The larger specimen may have had a stronger curve in the rostrum.

Doswellia is reported to have lost lateral temporal fenestrae, but tiny vestiges are still apparent (Fig. 1). Small antorbital fenestra are present, but they appear to be vestiges, on their way to disappearing, too. Choristoderes do not have antorbital fenestra.

FIgure 3. Proterosuchus (above) and Doswellia (below). Note the similarity of the drooping premaxilla, the shape of the pes and the overall low slung body.

FIgure 3. Proterosuchus (above) and Doswellia (below). Note the similarity of the drooping premaxilla, the shape of the pes and the overall low slung body.

The nares
are at the tip of the snout, but dorsolateral with a short premaxilla. We also see something like this in champsosaurus. The posterior portion of the ascending process of the premaxilla appears to be present, stuck to the side of the maxilla due to taphonomic forces.

This new reconstruction comes from transferring existing drawings using DGS (digital graphic segregation) to create a reconstruction. Color also helps.

And this is blog post #900.

References
Dilkes D and Sues H-D 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29(1):58-79
Heckert AB, Lucas SG and Spielmann JA 2012. A new species of the enigmatic archosauromorph Doswellia from the Upper Triassic Bluewater Creek Formation, New Mexico, USA. Palaeontology (Blackwell Publishing Ltd) 55(6): 1333-1348.
Sues H-D, Desojo JB and Ezcurra MD 2013. Doswelliidae: a clade of unusual armoured archosauriforms form the Middle and Late Triassic. Geological Society, London
Weems RE 1980. An unusual newly discovered archosaur from the Upper Triassic of Virginia, U.S.A. Transactions of the American Philosophical Society, New Series 70(7):1-53

wiki/Doswellia

2 thoughts on “The droopy snout of Doswellia

  1. Pingback: traiteur rabat

    • Better to go with the evidence than the expert. And you can check out the evidence yourself. Keeping the person, no matter their status, out of the equation is essential. Since this is science, we don’t _believe_ experts. We test their hypotheses. Confirmation is great. However, sometimes refutation happens, as you already know.

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