ALBERT

Description: Diandongosaurus acutidentatus Shang, Wu & Li, 2011 is restudied on the basis of a new specimen. The new specimen provides further information on the palate of the skull, the shoulder girdle, the gastralia and hind limbs, and permits revision of the diagnosis. Newly added or modified diagnostic characters include the presence of a few small vomerine teeth, the presence of an ectopterygoid, lateral elements of gastralia distally swollen and curving dorsally, boomerang-shaped interclavicle and clavicle with a distinct anterolateral process. Slight variations in the vertebral counts, girdle morphology, and phalangeal formulae are attributed to the intraspecific variations. A revised phylogenetic analysis demonstrates that Diandongosaurus is closely related to the Nothosauroidea and that certain Chinese taxa (e.g. Keichousaurus) previously affiliated with the Pachypleurosauridae are more closely related to the Nothosauroidea. The effect of inclusion or exclusion of fragmentary taxa in the phylogenetic analysis is observed in the branching pattern of the cladogram, but it has little effect on the morphological characterization of the major clades.

Description: Largocephalosaurus polycarpon Cheng et al. 2012a was erected after the study of the skull and some parts of a skeleton and considered to be an eosauropterygian. Here we describe a new species of the genus, Largocephalosaurus qianensis, based on three specimens. The new species provides many anatomical details which were described only briefly or not at all in the type species, and clearly indicates that Largocephalosaurus is a saurosphargid. It differs from the type species mainly in having three premaxillary teeth, a very short retroarticular process, a large pineal foramen, two sacral vertebrae, and elongated small granular osteoderms mixed with some large ones along the lateral most side of the body. With additional information from the new species, we revise the diagnosis and the phylogenetic relationships of Largocephalosaurus and clarify a set of diagnostic features for the Saurosphargidae Li et al. 2011. Largocephalosaurus is characterized primarily by an oval supratemporal fenestra, an elongate dorsal ‘rib-basket’, a narrow and elongate transverse process of the dorsal vertebrae, and the lack of a complete dorsal carapace of osteoderms. The Saurosphargidae is distinct mainly in having a retracted external naris, a jugal–squamosal contact, a large supratemporal extensively contacting the quadrate shaft, a leaf-like tooth crown with convex labial surface and concave lingual surface, a closed dorsal ‘rib-basket’, many dorsal osteoderms, a large boomerang-like or atypical T-shaped interclavicle. Current evidence suggests that the Saurosphargidae is the sister-group of the Sauropterygia and that Largocephalosaurus is the sister-group of the Saurosphargis–Sinosaurosphargis clade within the family.