Teraterpeton shifts toward Diandongosuchus

Recent work with the Diandongosuchus palate opened the door to reviewing the scoring for the enigmatic Teraterpeton (Fig. 1), originally (Sues 2003) considered a relative of Trilophosaurus largely due to its toothless beak and lack of a lateral temporal fenestra. Now Teraterpeton nests as a sister to Diandongosuchus. That clade is a sister clade to parasuchians, which also have dorsal nares. All were derived from the BPI 2871 specimen of Youngina, which shares their long snout.

Diandongosuchus (Li et al. 2012) wasn’t described until nine years after Teraterpeton so Sues (2003) could not have made this connection. Even so, Teraterpeton is so weird, it is no wonder it has remained an enigma for so long. Nesting such enigmas is exactly what the large reptile tree (not updated yet) is for. Earlier Teraterpeton nested with Tropidosuchus in the large reptile tree, not too far off from Diandongosuchus, but a mismatch that needed repairing. And Science marches on.

Figure 1. Diandongosuchus (above) compared to Teraterpeton (below). Note the similar scapula shapes and the way the posterior dorsal ribs terminate in a line. Both lack the flaring cheeks of parasuchians and Youngina. Teraterpeton, with so few teeth, could well have been a plant eater or anything but a carnivore. Hopefully we'll find more of this genus someday.

Figure 1. Diandongosuchus (above) compared to Teraterpeton (below). Note the similar scapula shapes and the way the posterior dorsal ribs terminate in a line. Both lack the flaring cheeks of parasuchians and Youngina. Teraterpeton, with so few teeth, could well have been a plant eater or anything but a carnivore. Hopefully we’ll find more of this genus someday.

Teraterpeton-skull-588

Figure 2. Teraterpeton skull. Note the confluent naris and antorbital fenestra.

 

Teraterpeton hrynewichorum (Sues 2003) Late Triassic, ~215 mya, was described as euryapsid (lacking a lateral temporal fenestra) and possibly related to the rhynchocephalian, Trilophosaurus on that basis. Here Teraterpeton is derived from Diandongosuchus, but with a stretched out rostrum and far fewer, smaller teeth. The lateral temporal fenestra has been shortened so much that the lateral temporal fenestra has closed up. So, it’s still a diapsid. Distinct from Diandongosuchus, the skull had a larger antorbital fenestra and a narrower configuration in dorsal view. The teeth had the multiple cusps of a plant eater. The pedal(?) unguals are robust, but note the disparate sizes, distinct from Diandongosuchus.

References
Li C, Wu X-C, Zhao L-J, Sato T and Wang LT 2012. A new archosaur (Diapsida, Archosauriformes) from the marine Triassic of China, Journal of Vertebrate Paleontology, 32:5, 1064-1081.
Sues H-D 2003. An unusual new archosauromorph reptile from the Upper Triassic Wolfville Formation of Nova Scotia. Canadian. Journal of Earth Science 40(4): 635-649.

 

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