Avialae

Avialae ("bird wings") is a clade of archosaurianvertebrates containing the only living branch of dinosaurs, the birds (class Aves), and their closest relatives. It is usually defined as all theropod dinosaurs more closely related to birds than to deinonychosaurs, though alternative definitions are occasionally used (see below).

Archaeopteryx lithographica, from the late Jurassic PeriodSolnhofen Formation of Germany, is usually considered the earliest known avialan which may have had the capability of powered flight; a minority of studies have suggested that it might have been a deinonychosaur instead. Several older (but non flight-capable) possible avialans are known from the late Jurassic Tiaojishan Formation of China, dated to about 160 million years ago.