Of course this doubleheaded condition is the more primitive, and as such exists in most nidifugous birds, but in many of these, as well as in many nidicolous birds, either the caudal or the iliac head is absent, and in a very few (Cancroma, Dicholophus, Steatornis and some Cathartes) the whole muscle is absent.
The syrinx or lower larynx is the most interesting and absolutely avine modification, although absent as a voice-producing organ (probably due to retrogression) in most Ratitae, storks, turkey buzzards (Cathartes) and Steganopodes.
Cathartes, turkey buzzards, Sarcorhamphus gryphus, condor Gypagus papa, king vulture.
The best known vulture is the common urubu (Cathartes foetens, Illig), which is the universal scavenger of the tropics.
Among the vultures the turkey-buzzard group (Rhinogryphus or Cathartes), including the R.