At the nothosaur/plesiosaur node

A cover story and rapid communication in the latest Journal of Vertebrate Paleontology features Wangosaurus (Ma et al. 2015, Fig. 1), a long-necked, short-faced sauropterygian with short fingers and toes.

[Unfortunately, Wangosaurus in the urban dictionary is “a complete jackass.”] But let’s concentrate on the fossil, which is virtually complete and wonderfully preserved.

Figure 1. Wangosaurus. Click to enlarge.

Figure 1. Wangosaurus. Click to enlarge. Note the short fingers and toes.

Sister taxa
In the Ma et al paper, Wangosaurus nested as a sister Yungisaurus (Figs. 2, 3) and both were considered pistosaurids, the clade transitional between nothosaurs and plesiosaurs, despite their morphological differences.

Figure 2. The Ma et al. tree that nested Wangosaurus with Yungisaurus as a pistosaurid. Colors were added. Yellow = enaliosauria in the large reptile tree. Blue = protorosaurs + archosauriformes. Pink = lepidosauromorphs.

Figure 2. The Ma et al. tree that nested Wangosaurus with Yungisaurus as a pistosaurid. Colors were added. Yellow = enaliosauria in the large reptile tree. Blue = protorosaurs + archosauriformes. Pink = lepidosauromorphs.

In the large reptile tree (subset Fig. 4), Yungisaurus also nests between Pistosaurus and Plesiosaurus, but Wangosaurus nests in a much more basal node, between nothosaurs and Simosaurus, still close to the nesting in the Ma et al. paper (Fig. 2).

Figure 3. Yungisaurus in situ and closeups of the skull and flippers.

Figure 3. Yungisaurus in situ and closeups of the skull and flippers. This is a much larger sauropterygian with longer toes transformed into flippers. Interesting to see the rear flippers larger than the forelimbs. So does that tell us something about their swimming technique?  

The Ma et al. tree is based on earlier work by Jiang et al. (2014 – featuring the basal placodont Majianshanosaurus), which is an updated version of Neenan et al. (2013). Note the differences in the skulls of Wangosaurus and Yungisaurus. Those don’t look like close relatives to me and their scores confirm those suspicions.

 

Figure 4. The enaliosaur/marine reptile subset of the large reptile tree. Note there are intervening taxa here between Wangosaurus and Youngisaurus.

Figure 4. The enaliosaur/marine reptile subset of the large reptile tree. Note there are intervening taxa here between Wangosaurus and Youngisaurus.

The Ma et al. tree employs suprageneric taxa (always a problem). You’ll note that turtles and lepidosauriformes are the proximal outgroup taxa to sauropterygians here. That is not supported by the large reptile tree. I also find it odd that the marine reptiles Claudiosaurus and Hovasaurus nest so far from the rest of their natural clade in the Ma et al. tree, and separate from one another.

References
Cheng Y-N,  Sato T, Wu X-C and Li C 2006. First complete pistosaurid from the Triassic of China. Journal of Vertebrate Paleontology 6(2):501-504.
Ma L-T, Jiang D-Y, Rieppel O, Motani R and Tintori A 2015.
A new pistosaurid (Reptilia, Sauropterygia) from the late Landinian Xingyi marine reptile level, southwestern China. Journal of Vertebrate Paleontology 35(1): e881832.

 

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