Philydrosaurus: another basal choristodere

Figure 1. Philydrosaurus in several views. This specimen nests as the most basal small, short-snouted choristodere. Juveniles surround it. DGS indicates this specimen had lateral temporal fenestrae, but greater resolution may modify this hypothesis.

Figure 1. Philydrosaurus in several views. This specimen nests as the most basal small, short-snouted choristodere. Juveniles surround it. DGS indicates this specimen had lateral temporal fenestrae, but greater resolution may modify this hypothesis.

Philydrosaurus proseilus (Gao and Fox 2005, Early Cretaceous, scale bar = 2 cm) is a basal choristodere with distinct ridges on the skull over the orbits. The lateral temporal fenestra is reported as closed, but the low-resolution image provided appears to show lateral temporal fenestra. It was scored without them. The cervicals do not decrease toward the skull. Several juveniles were found associated with the presumed mother. The right skull (above) does not seem to accurately reflect the fossil. Higher resolution images have been requested.

Figure 2. Philydrosaurus compared to the BPI 2871 specimen wrongly assigned to Youngina, itself a descendant of Proterosuchus.

Figure 2. Philydrosaurus compared to the BPI 2871 specimen wrongly assigned to Youngina, itself a descendant of Proterosuchus.

Update:
The blogpost on Nundasuchus has been updated with a new reconstruction (Fig. 3) and nesting with Qianosuchus and Ticinosuchus, also reflected at reptileevolution.com.

Figure 1. from Nesbitt et al. 2014. Plus foot reconstructed here and closeups of the mandible and tooth.

Figure 3. from Nesbitt et al. 2014. Plus foot reconstructed here and closeups of the mandible and tooth.

References
Gao K-Q and Fox RC 2005. A new choristodere (Reptilia: Diapsida) from the Lower Cretaceous of western Liaoning Province, China, and phylogenetic relationships of Monjurosuchidae. Zoological Journal of the Linnean Society 145 (3): 427–444.

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