Cheng et al. (2012) described their new specimen, Largocephalosaurus (Fig. 1), as a basal eosauropterygian, most closely related to Wumengosaurus. Unfortunately Cheng et al. (2012) did not include Sinosaurosphargis, its closest sister here in their analysis. Even so, Largocehalosaurus is indeed a basal sauropterygian.
Like Sinosaurosphargis, But Without the Carapace
Largocephalosaurus shares a nearly identical skull and humerus with Sinosaurophargis (Fig. 2). The upper temporal fenestra was larger. The straight squamosal entered the orbit, if only slightly. The naris was larger. Manual digit 5 was longer, which is an autapomorphy.
Stereosternum, a mesosaur, was the outgroup taxon. It was also ignored by Cheng et al. (2012). Essentially Largocephalosaurus was a large, low, wide mesosaur with a relatively shorter rostrum.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
Cheng L, Chen X-H, Zeng X-W and Ca Y-J 2012. A new eosauropterygian (Diapsida: Sauropterygia) from the Middle Triassic of Luoping, Yunnan Province. Journal of Earth Science 23 (1): 33-40.
Li C, Rieppel O, Wu X-C, Zhao L-J and Wang LT 2011. A new Triassic marine reptile from southwestern China. Journal of Vertebrate Paleontology 31 (2): 303-312. doi:10.1080/02724634.2011.550368.