Shuvosaurus inexpectatus ( Chatterjee, 1993 )

Nesbitt, Sterling J., 2011, The Early Evolution Of Archosaurs: Relationships And The Origin Of Major Clades, Bulletin of the American Museum of Natural History 2011 (352), pp. 1-292 : 32

Shuvosaurus inexpectatus ( Chatterjee, 1993) , sensu Nesbitt and Norell, 2006 5 Chatterjeea elegans Long and Murry, 1995

AGE: Norian, Late Triassic ( Lehman and Chatterjee, 2005).

OCCURRENCE: Post (5 Miller) Quarry, Cooper Canyon Formation, Dockum Group ( Chatterjee, 1985).

HOLOTYPE: TTU-P 9280, disarticulated skull.

PARATYPE: TTU-P 9281, anterior portion of dentries; TTU-P 9282, braincase and other cranial fragments.

REFERRED MATERIAL: TTU-P 9001, much of a postcranial skeleton, hundreds of disarticulated and associated bones from the Post (5 Miller) Quarry (material referred to Chatterjee elegans ).

REMARKS: Chatterjee (1993) named Shuvosaurus inexpectatus based on associated bizarre cranial elements from the Post (5 Miller) Quarry. Chatterjee (1993) concluded that the large orbits, seemingly pneumatic braincase, and edentulous maxillae, premaxillae, and dentaries of the taxon allied it to ornithomimid dinosaurs. The resultant phy- logenetic position indicated that much of the theropod diversity in the Cretaceous was the product of diversification in the Triassic ( Rauhut, 1997). However, the absence of coelurosaurian or tetanuran synapomorphies made others (e.g., Rauhut, 2003) question Chatterjee’s (1993) original assignment. Long and Murry (1995) named Chatterjeea elegans based on distinctive postcranial remains from the same quarry and suggested that Shuvosaurus may be the skull of Chatterjeea . Nesbitt and Norell (2006) used the articulat- ed skeleton of Effigia to demonstrate that the skull of Shuvosaurus indeed belongs to the body of Chatterjeea . Here, the scorings of Shuvosaurus and Chatterjeea are combined, and only unambiguous material from the Post (5 Miller) Quarry is scored.

Long and Murry (1995) referred material to ‘‘ Chatterjeea ’’ throughout the Chinle Formation and the Dockum Group. Much of the material consists of isolated finds. Given that Effigia and Shuvosaurus are very similar but distinct taxa, most of these can be assigned only to the clade containing the two taxa.

Shuvosaurus inexpectatus is distinguished from all other suchians except Effigia by the presence of an edentulous premaxilla, maxilla, and dentary, a posteriorly long anterodorsal process of the premaxilla, a long preacetabular process of the ilium that connects to the posterior process by a large, thin flange, and a pubic boot that is 33% the length of the pubic shaft. It is distinguished from Effigia by the absence of both a dorsal and posterior process of the maxilla, relatively longer dentary, the presence of a posterior process of the squamosal, the absence of a small fossa on the posterolateral side of the squamosal, and the absence of a large pit on the posterior side of the lacrimal.

KEY REFERENCES: Chatterjee, 1993; Long and Murry, 1995; Rauhut, 1997; Nesbitt and Norell, 2006; Nesbitt et al., 2007; Nesbitt, 2007.