Avicephala ("bird heads") is a potentially polyphyletic grouping of extinct diapsid reptiles that lived during the Late Permian and Triassic periods characterised by superficially bird-like skulls and arboreal lifestyles.

Drepanosaurs possess a suite of chameleon-like skeletal features, such as opposable digits on the hands and feet and prehensile tails—tipped with a bony hook in some genera like Drepanosaurus.

Although both groups are highly derived, they do share some similarities, namely they have relatively unossified skeletons lacking intercentra between their vertebrae, as well as proportionately tall, thin shoulder blades.

They identified four unambiguous synapomorphies (shared unique traits) supporting Avicephala: the absence of both cervical and dorsal intercentra, a length/height ratio for the scapula between 0.4 and 0.25, and no outer process on the fifth metatarsal.

Avicephala is now cladistically defined as "including all taxa more closely related to Weigeltisaurus jaekeli Weigelt 1930 and Drepanosaurus unguicaudatus Pinna 1979 than to Petrolacosaurus kansensis Lane 1945, Orovenator mayorum Reisz, Modesto & Scott, 2011, Claudiosaurus germaini Carroll, 1978, Youngina capensis Broom 1914, or Sauria Macartney 1802".

[2] Buffa et al. argued that most of the shared traits both Senter and Pritchard proposed to unite Avicephala were commonly distributed enough throughout diapsids to be congruent with multiple possible evolutionary scenarios, while others were less similar between the two than previously thought (such as the nature of the inclined rear margin of the skull).

[2] Pritchard et al. (2021): Monophyletic Avicephala[5] Petrolacosaurus Orovenator Claudiosaurus Hypuronector Vallesaurus Dolabrosaurus Megalancosaurus Drepanosaurus Avicranium Coelurosauravus Weigeltisaurus Rautiania Sauria Younginidae Tangasauridae Buffa et al. (2024): Non-monophyletic Avicephala[2] Younginiformes Claudiosaurus Rautiania Coelurosauravus Weigeltisaurus Lepidosauromorpha Icarosaurus Protorosaurus Tanystropheidae Azendohsauridae Trilophosauridae Hypuronector Avicranium Vallesaurus Dolabrosaurus Megalancosaurus Drepanosaurus Prolacerta Rhynchosauria Archosauriformes