Shuvosaurus (meaning "Shuvo [Chatterjee]'s lizard")[1] is a genus of beaked, bipedal poposauroid pseudosuchian from the Late Triassic (early to middle Norian) of western Texas.

[3] Upon its description, Chatterjee tentatively interpreted Shuvosaurus as a Triassic member of Ornithomimosauria, a group of theropod dinosaurs otherwise known only from the Cretaceous, due to similar construction of the skull, including toothless jaws and large eye sockets.

[2] As with the contemporary purported avian Protoavis and Postosuchus,[b] Chatterjee's proposed affinities of a Late Triassic Post Quarry taxon to Cretaceous coelurosaurs invoked a long ghost lineage and was consequently greeted with scepticism by other researchers (such as Halszka Osmólska in 1997).

[7] The Shuvosaurus skulls were found mixed in with postcranial remains of small pseudosuchians from the Post Quarry—all lacking heads—which Chatterjee had previously described as juveniles of the large predatory rauisuchid Postosuchus (of which the fossils were also associated with) in 1985.

However, in a 1995 monograph on Late Triassic tetrapods from the American Southwest, Robert Long and Philip Murry regarded this material as so "radically different" from Postosuchus that they identified it as a new taxon of gracile "rauisuchian" allied to poposaurids (i.e. Poposaurus) which they named Chatterjeea elegans—named after Sankar Chatterjee and from Latin elegans for "very fine" or "beautiful".

[4][9][10] In the early 2000s, Sterling Nesbitt and Mark Norell prepared previously unopened plaster-jackets of an unknown archosaur collected from the Whitaker Quarry at Ghost Ranch which combined a Shuvosaurus-like skull with Chatterjeea-like postcrania that they named Effigia in 2006.

[3] Many isolated shuvosaurid remains found in rocks of the southwestern US from throughout the Late Triassic have been referred to Shuvosaurus (including to Chatterjeea), namely from elsewhere in the Dockum Group and the Chinle Formation to the west.

In an early report of its discovery at the annual Society of Vertebrate Paleontology meeting in 1991 Chatterjee even explicitly referred Shuvosaurus to the derived ornithomimosaur family Ornithomimidae.

This was in part based on the presence of at least two inferred primitively ancestral (i.e. plesiomorphic) traits (no parasphenoid capsule and a smaller brain cavity) compared to Cretaceous ornithomimosaurs, as well as its general distinctiveness relative to them.

[1][5] Chatterjee supported his argument with an early cladistic analysis of theropods (modelled on the phylogeny of Gauthier, 1986)[16] in which Shuvosaurus possessed almost the entire suite of derived cranial characteristics in ornithomimosaurs in the dataset and as such was recovered in that clade.

[7] Hunt et al. (1998) and Heckert & Lucas (1998) went even further and argued that although Chatterjee (1993) compared specific features of Shuvosaurus strongly to ornithomimosaurs, he had not demonstrated that the skull was definitively even that of a dinosaur in the first place.

[20] Phylogenetic analyses since then consistently find Shuvosaurus and Effigia as sister taxa, and together with Sillosuchus make up the re-defined family and clade of Shuvosauridae deeply nested within Poposauroidea.