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 Proterosuchus and otherwise close to Champsosaurus, Simoedosaurus and Diandongosuchus.
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). In lockstep with this new droopy reconstruction, phylogenetically Doswellia was preceded by similar droopy-snouted taxa, like Proterosuchus and Youngina (Figs. 3, 4).
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.
are at the tip of the snout, but completely dorsal, elevated by the rising and wrapping of the lateral premaxillary processes. We also see something like this in Simoeodsaurus.
Perhaps the expanded rostral tip was something on the order of what one finds in aetosaurs, which may have used that hog-nose like structure to root in the substrate.
The addition of several choristoderes to the large reptile tree slightly shifted Proterosuchus and Youngoides UC1528 to the very base of the Archosauriformes, whereas before Youngina (Fig. 1) was the outgroup to the two major archosauriform clades.
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.
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