MEANING: Pharaoh's dawn chicken
PERIOD: Late Cretaceous
CONTINENT: North America
Eoneophron is a caenagnathid theropod dinosaur from the Late Cretaceous Hell Creek Formation of North America. Caenagnathids can be differentiated from other oviraptorosaurs by their distinct jaws, which tended to be relatively long and shallow, suggesting that the bite was not as powerful. Caenagnathids also tended to be more lightly built. They had slender arms and long, gracile legs, although they didn't seem to be especially cursorial. Eoneophron's body mass is estimated at approximately 78 kg.
Abstract from paper: Caenagnathidae is a clade of derived, Late Cretaceous oviraptorosaurian theropods from Asia and North America. Because their remains are rare and often fragmentary, caenagnathid diversity is poorly understood. Anzu wyliei is the only caenagnathid species currently described from the late Maastrichtian Hell Creek Formation of the USA and is also among the largest and most completely preserved North American caenagnathids. Smaller, less complete caenagnathid material has long been known from the Hell Creek Formation, but it is unclear whether these are juvenile representatives of Anzu or if they represent distinct, unnamed taxa. Here, we describe a relatively small caenagnathid hindlimb from the Hell Creek Formation, and conduct osteohistological analysis to assess its maturity. Histological data and morphological differences from Anzu wyliei and other caenagnathids allow us to conclude that this specimen represents a new species of caenagnathid from the Hell Creek Formation, with a smaller adult body size than Anzu. This new taxon is also distinct from other small caenagnathid material previously described from the area, potentially indicating the coexistence of three distinct caenagnathid species in the Hell Creek Formation. These results show that caenagnathid diversity in the Hell Creek ecosystem has been underestimated.
Eoneophron is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Eoneophron is an oviraptorosaur. Oviraptorosauria is a group of feathered theropod dinosaurs from the Cretaceous Period of what are now Asia and North America. They are known for their short, beaked, parrot-like skulls and bony crests that many had atop the head. They ranged in size from the turkey-sized Caudipteryx, to the 8-meter-long, 1.4-ton Gigantoraptor.
Oviraptorosaurs are closely related to birds. They had shortened beaklike jaws, and few or no teeth. The long hands typically had three long fingers each. Their tails are very short compared to other maniraptorans, and show evidence of fused vertebrae, which imply the presence of a fan of feathers. Fossilized remains have been found with impressions of well developed feathers, most notably on the wings and tail, suggesting that they functioned at least partially for display.
A number of oviraptorid specimens have been discovered in a nesting position similar to that of modern birds. The arms of these specimens are positioned in such a way that they could perfectly cover their eggs if they had small wings and a substantial covering of feathers.