Matsayi na farko da aka ba Mantell, wanda ya ƙi saboda rashin lafiya, kuma hangen nesa na Owen daga baya ya zama tushen abin da sassaka ya samo asali. An bayyana siffar bipedal dinsa tare da gano halittar Bernatons. Duk da haka, an nuna shi a matsayin madaidaiciya, tare da wutsiya mai wutsiya hudu, kamar yadda aka gano wasu ƙasusuwa, Mantell ya lura cewa gabobin gaba sun fi ƙananan ƙananan ƙafafun baya.
Mantell