A juvenile specimen of Saurornithoides mongoliensis from the Upper Cretaceous of northern China

Abstract

A hind limb of Saurornithoides mongoliensis from the Djadokhta Formation equivalent beds (Upper Cretaceous) of Bayan Mandahu (People's Republic of China) provides more information on the anatomy of the leg of this species than any other known specimen. Although it shares apomorphies of all troodontid theropods, the metatarsus is relatively longer and more derived than that of Troodon itself. The specimen is of an immature individual, less than half the size of the holotype. The degree of ossification suggests that troodontids were well developed at birth and that parental care was probably unnecessary.