What is Sinosaurosphargis?

The Enaliosauria, including Phonodus nesting with Placochelys and Henodus.

Figure 1. The Enaliosauria, including Sinosaurosphargis. Click to enlarge.

Sinosaurosphargis (Li et al. 2011, Fig. 1) was yet another turtle-like Middle Triassic placodont, not related to the better known turtle-like placodonts, Placochelys and Henodus. According to phylogenetic analysis, Sinosaurosphargis derived its carapace independently. Li et al. (2011) determined that the upper temporal fenestra was secondarily closed, but illustrated it as tiny and both fenestrae appear visible with palatal bones filling the void from below.

In the large study, Sinosaurosphargis nested at the base of the Placodontia (Fig. 2). Placochelys and Henodus nested as more derived taxa. Sinosaurosphargis was derived from a sister to Claudiosaurus. Because of its basal position, Sinosaurosphargis was also a sister to Stereosternum and Pachypleurosaurus.

Details
Distinct from Claudiosaurus, the skull of Sinosaurosphargis was longer with a smaller naris raised to the top of the rostrum. The maxilla was larger with a broad ascending process. The lacrimal was smaller. The squamosal contacted the jugal. The postfrontal and postorbital were fused together. The parietals were fused. The teeth were convex onthe cheek side and concave on the tongue side. The number of cervicals appears to be fewer than six. The cervical series was shorter than the skull. Each dorsal vertebrae included an elongated transverse process and a broad flat rib. The enlarged gastralia were also expanded similarly. The scapula was not fused to the coracoid. The interclavicle was a broad T-shape. The humerus was strongly curved distally and was twice the length of the reduced but robust ulna. The unguals were reduced to nubs.

Sinosaurosphargis.

Figure 2. Sinosaurosphargis. Click for more information.

Saurosphargis
A purported sister (according to Nosotti and Rieppel 2003), Saurosphargis volzii (Huene 1936, Middle Triassic), was described from disassociated parts that were destroyed in bombing raids during WWII. I haven’t seen much of this, so I’ll wait for the paper.

 Eusaurosphargis.

Figure 2. Eusaurosphargis, a thalattosaur related to Helveticosaurus, not Sinosaurosphargis. Click for more information.

Eusaurosphargis
Eusaurosphargis dalsassoi (Nosotti and Rieppel 2003) Middle Triassic, ~240 mya, ~20 cm snout to vent length, was considered more closely related to Helveticosaurus than to placodonts and to nest outside of the Thalattosauriformes. Half true. Here Eusaurosphargis nested between Miodentosaurus and Helveticosaurus, both within the Thalattosauriformes. Nosotti and Rieppel (2003) nested Sinosaurosphargis with Saurosphargis as a sister to the Thalattosauriformes, which is not confirmed here (Fig. 1). Also notice the shared traits in the skull of this taxon and Vancleavea.

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.

References
Huene F von 1936. Henodus chelydrops, ein neuer Placodontier. Palaeontographica A, 84, 99-147.
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.
Nosotti S and Rieppel O 2003. Eusaurosphargis dalsassoi n.gen. n.sp., a new, unusual diapsid reptile from the Middle Triassic of Besano (Lombardy, N Italy). Memories of the Italian Society of Natural Science and the Museum of Natural History in Milan, XXXI (II).

wiki/Eusaurosphargis
wiki/Sinosaurosphargis

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2 thoughts on “What is Sinosaurosphargis?

  1. I work on placodont phylogeny, and I’m sorry to say that Sinosaurosphargis cannot in any way be considered a placodont. Yes it has dermal armour, but of a very different type to that of cyamodontoidea. Sinosaurosphargis (the holotype and paratype of which I studied in the IVPP last month) is missing various morphological characters that would relate it to Placodontia, and has a suite of features not present in placodonts. Please be more careful with your classification, as you clearly have not read the literature thoroughly and/or have not examined the specimens yourself. Students could easily find this page and get very confused.

    • James, where do you nest Sinosaurosphargis? I tested it against several hundred other reptiles and this was the most parsimonious nesting, at the very base of the Placodontia, perhaps outside the Placodontia itself, a sister to Claudiosaurus.

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