Cretaceous birds

The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over seventy species of Enantiornithes have been named, but some names represent only single bones, so it is likely that not all are valid. The Enantiornithes became extinct at the Cretaceous–Paleogene boundary, along with Hesperornithes and all other non-avian dinosaurs.

Avisauridae is a family of extinct enantiornithine dinosaurs from the Cretaceous period, distinguished by several features of their ankle bones. Depending on the definition used, Avisauridae is either a broad and widespread group of advanced enantiornithines (following Cau & Arduini, 2008), or a small family within that group, restricted to species from the Late Cretaceous of North and South America (following Chiappe, 1992).

Yungavolucris is a genus of enantiornitheans. It contains the single species Yungavolucris brevipedalis, which lived in the Late Cretaceous (Maastrichtian, c.70.6 – 66 mya). The fossil bones were found in the Lecho Formation at estancia El Brete, Argentina."Yungavolucris brevipedalis" means "Short-footed Yungas bird". The generic name, Yungavolucris is after the Yungas region + the Latin volucris, which translates to "bird" (literally "flyer"). The specific name brevipedalis is from the Latin brevis, which means "short", + pedalis, from the Latin pes, meaning "foot".

Gobipterygidae is a family of extinct enantiornithine birds known from the Cretaceous of Asia.

Ambiortiformes is a group of prehistoric ornithuromorph dinosaurs. ==Cladistic analyses== The first species to be included, Ambiortus dementjevi, lived sometime during the Barremian age between 136.4 and 125 million years ago in today's Mongolia. A. dementjevi belongs to the Ornithuromorpha (the group containing modern birds but not enantiornithes), according to all published cladistic analyses. However, the exact position of the species within this group has been controversial. Most analyses have found it to be either an unresolved member of the Ornithurae, or a more primitive member of Ornit