A new oviraptorosaur from the Lower Cretaceous Miaogou Formation of western Inner Mongolia, China

A new oviraptorosaur, Yuanyanglong bainian gen. et sp. nov. is described based on two specimens recovered from the Lower Cretaceous Miaogou Formation of the Maortu locality in Chilantai, Inner Mongolia, China. This new species is intermediate in morphology between the earliest-diverging and late-diverging oviraptorosaurs, and our phylogenetic analysis supports it as a sister taxon to the clade formed by Avimimidae and Caenagathoidea. Notably, this new early-diverging oviraptorosaur has an ilium with an extremely short postacetabular process and hindlimbs with proportionally elongate and fused lower segments, a character combination unknown among other oviraptorosaurs but common in wading birds, suggesting a potential ecology involving wading. Preserved gastroliths similar to Caudipteryx suggest a gastric mill function in our new species, and our preliminary observations indicate potential discrepancies in the digestion mode of early- and late-diverging oviraptorosaurs.