Eutreptornis ("changing bird")is a genus of extinct possible cariamiforme bird from the Late

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

. It is traditionally considered to be a

bathornithid Bathornithidae is an extinct family of birds from the Eocene to Miocene of North America. Part of Cariamiformes, they are related to the still extant seriemas and the also extinct Phorusrhacidae. They were likely similar in habits, being terre ...

, though a combination of the relative incompleteness of the material alongside some differences from other bathornithids have raised some suspicions about this affiliation.

Description

''Eutreptornis'' is currently represented by a single type species, ''E. uintae'', in turn represented by a

tibiotarsus The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia. A similar structure also occurred in the Mesozoic Heterodontosauridae. These s ...

and tarsometatarsus from the Uinta Formation of

Biology

It is represented by the smallest bathornithid remains known. Due to the incompleteness of its remains it is unclear whereas it was flightless like other bathornithids. It was, however, most certainly a terrestrial predator, perhaps akin to its closest living relatives, the

seriemas The seriemas are the sole living members of the small bird family Cariamidae, which is also the only surviving lineage of the order Cariamiformes. Once believed to be related to cranes, they have been placed near the falcons, parrots and passer ...

Ecology

''Eutreptornis'' co-existed with a rich mammalian megafauna, such as the

brontothere Brontotheriidae is a family (biology), family of extinct mammals belonging to the order Perissodactyla, the order that includes horses, rhinoceroses, and tapirs. Superficially, they looked rather like Rhinoceros, rhinos, although they were actua ...

Megacerops ''Megacerops'' ("large-horned face", from '' méga-'' "large" + '' kéras'' "horn" + '' ōps'' "face") is an extinct genus of the prehistoric odd-toed ungulate (hoofed mammal) family Brontotheriidae, an extinct group of rhinoceros-like browsers ...

'', as well as other terrestrial birds, including other bathornithid birds such as the larger '' Bathornis'' species and the flightless crane-like geranoidids.Joel Cracraft, Systematics and evolution of the Gruiformes (Class Aves). 2, Additional comments on the Bathornithidae, with descriptions of new species. ''American Museum Novitates''; no. 2449

References

{{Taxonbar, from=Q25095786 Bathornitidae Eocene birds Bird genera Paleogene birds of North America Taxa named by Joel Cracraft