Thus he separates the birds of prey into three great groups - (I) the ordinary Diurnal forms, including the Falconidae and Vulturidae of the systematist of his time; but distinguishing the American Vultures from those of the Old World; (2) Gypogeranus, the secretary-bird; and (3) the owls (q.v.).
In some external characters the lammergeyer is intermediate between the families Vulturidae and Falconidae, and the opinion of systematists has from time to time varied as to its proper position.
It is now generally agreed, however, that it is more closely allied with the eagles than with the vultures, and the sub-family Gypaetinae of the Falconidae has been formed to contain it.