Abstract
The oviraptorosaurian theropod dinosaur clade Caenagnathidae has long been enigmatic due to the incomplete nature of nearly all described fossils. Here we describe Anzu wyliei gen. et sp. nov., a new taxon of large-bodied caenagnathid based primarily on three well-preserved partial skeletons. The specimens were recovered from the uppermost Cretaceous (upper Maastrichtian) Hell Creek Formation of North and South Dakota, and are therefore among the stratigraphically youngest known oviraptorosaurian remains. Collectively, the fossils include elements from most regions of the skeleton, providing a wealth of information on the osteology and evolutionary relationships of Caenagnathidae. Phylogenetic analysis reaffirms caenagnathid monophyly, and indicates that Anzu is most closely related to Caenagnathus collinsi, a taxon that is definitively known only from a mandible from the Campanian Dinosaur Park Formation of Alberta. The problematic oviraptorosaurs Microvenator and Gigantoraptor are recovered as basal caenagnathids, as has previously been suggested. Anzu and other caenagnathids may have favored well-watered floodplain settings over channel margins, and were probably ecological generalists that fed upon vegetation, small animals, and perhaps eggs.
Highlights
Oviraptorosauria is a clade of maniraptoran theropod dinosaurs with peculiar craniomandibular specializations [1]
Whereas most recent analyses have interpreted oviraptorosaurs as non-avian maniraptorans, a few others have postulated these theropods as basal birds [27,28,29] or as the sister taxon of Scansoriopterygidae [30,31], a clade of unusual Jurassic maniraptorans that are frequently placed as basal avians [32,33]
When considered in light of very small-bodied taxa such as Caenagnathasia and Elmisaurus elegans [73], it appears highly likely that caenagnathids encompassed a much greater range of body sizes than did other oviraptorosaurs, and many other non-avian theropod groups
Summary
Oviraptorosauria is a clade of maniraptoran theropod dinosaurs with peculiar craniomandibular specializations [1]. Most if not all oviraptorosaurs were feathered, as evidenced by direct preservation [2,8,9], possible quill knobs on the ulna [10], or pygostyle-like terminal caudal vertebrae [11,12,13,14]. Oviraptorosaurs brooded their nests [15,16,17,18,19,20], employed a reproductive strategy intermediate between those of crocodylians and birds [21], had bird-like brains [22,23] (but see [24]), and were probably omnivorous or herbivorous [5,7,25,26]. Whereas most recent analyses have interpreted oviraptorosaurs as non-avian maniraptorans, a few others have postulated these theropods as basal birds [27,28,29] or as the sister taxon of Scansoriopterygidae [30,31], a clade of unusual Jurassic maniraptorans that are frequently placed as basal avians [32,33]
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