ch ▁in ▁trees . ▁They ▁argued ▁that ▁an ▁ar b ore al ▁habit ▁was ▁most ▁likely ▁for ▁all ▁of ▁the ▁A vis aur idae . ▁ ▁History ▁and ▁classification ▁ ▁A vis aur idae ▁was ▁ere cted ▁as ▁a ▁family ▁by ▁Bre tt - Sur man ▁and ▁Paul ▁in ▁ 1 9 8 5 . ▁At ▁that ▁time ▁the ▁family ▁consisted ▁of ▁a ▁few ▁foss ils ▁that ▁they ▁believed ▁belonged ▁to ▁small ▁non - av ian ▁din osa urs . ▁They ▁doubt ed ▁that ▁these ▁foss ils ▁belonged ▁to ▁birds ▁due ▁to ▁the ▁presence ▁of ▁several ▁features ▁of ▁the ▁t ars omet at ars us . ▁In ▁A vis aur us ▁( the ▁only ▁av is aur id ▁known ▁at ▁that ▁time ), ▁only ▁the ▁proxim al ▁parts ▁of ▁the ▁met at ars als ▁were ▁f used , ▁the ▁proxim al ▁part ▁of ▁met at ars al ▁III ▁was ▁wide , ▁and ▁the ▁hyp ot ars us ▁( a ▁wide ▁r idge ▁extending ▁down ▁the ▁back ▁of ▁the ▁t ars omet at ars us ) ▁was ▁poor ly ▁developed . ▁ ▁However , ▁Ch ia ppe ▁later ▁re ass igned ▁the ▁A vis aur idae ▁to ▁the ▁class ▁A ves ▁( which ▁is ▁equivalent ▁to ▁the ▁cla de ▁Av ial ae ▁in ▁modern ▁usage ) ▁and ▁the ▁subclass ▁En anti orn ith es ▁in ▁ 1 9 9 2 . ▁He ▁noted ▁that ▁the ▁features ▁used ▁to ▁exclude ▁av is aur ids ▁from ▁birds ▁are ▁in ▁fact ▁present ▁in ▁some ▁early ▁birds ▁such