Hupehsuchus nanchangensis (Young and Dong 1972, Carroll and Dong 1991) Early Triassic ~242 mya, ~1 m in length was originally and is currently considered an enigma with no obvious close relations. Here Hupehsuchus was derived from Wumengosaurus and was a sister to the basal ichthyopterygid Thaisaurus.

Compared to Wumengosaurus, the skull of Hupehsuchus had a longer, flatter rostrum without teeth. The premaxilla was longer than the maxilla. The lacrimal and prefrontal were smaller. The posterior skull was shorter and taller. The quadratojugal was restricted to the quadrate. The palate was further modified toward the ichthyosaur configuration.

The cervicals were shorter. The dorsals neural spines were were much taller and topped with ossifications that further increased their height. The dorsal ribs were thinner and enclosed a deep, round torso. The tail was deeper with shorter caudals. The transverse processes were reduced.

The scapula and coracoid are not fused. The clavicle reached the top of the scapula. The humerus was reduced to a small stout rectangle with a concave posterior rim. An extra finger was present between #4 and #5, essentially duplicating #4. The unguals were reduced to discs and the entire hand was likely transformed into a paddle that was much larger than the foot.

The ilium was reduced, as was the hind limb. All five digits were aligned. This was made possible by addng phalanges (hyperphalangy) to the medial digits and subtracting one from digit IV. It appears likely that the hind limbs was also tranformed into a flipper.

Carroll RL and Dong Z-M 1991. Hupehsuchus, an enigmatic aquatic reptile from the Triassic of China, and the problem of establishing relationships. Philosophical Transactions of the Royal Society London B 28 331:131-153.

Chen X-H, Motani R, Cheng L, Jiang D-Y and Rieppel O 2014. A Carapace-Like Bony 'Body Tube' in an Early Triassic Marine Reptile and the Onset of Marine Tetrapod Predation. PLoS ONE. 9 (4): e94396. doi:10.1371/journal.pone.0094396. PMC 3981804

Chen X-H, Motani R, Cheng L, Jiang D-Y and Rieppel O 2015. A new specimen of Carroll’s mystery hupehsuchian from the Lower Triassic of China. PLoS One 10, e0126024, https://doi.org/10.1371/journal.pone.0126024 (2015).

Cheng L, Motani R, Jiang D-Y, Yan C-B, Tintori A and Rieppel O 2019. Early Triassic marine reptile representing the oldest record of unusually small eyes in reptiles indicating non-visual prey detection. Nature Scientific Reports Published online January 24, 2019.

Young C-C and Dong Z-M 1972. On the aquatic reptiles of the Triassic in China. Vertebrate Paleontology Memoirs. 9-1-34.

wiki/Hupehsuchus
wiki/Parahupehsuchus
wiki/Hupehsuchia
wiki/Eretmorhipis