PHORORHACOS, the best-known genus of the extinct Patagonian Stereornithes (see Bird: Fossil). Among the bones found in the strata of the Santa Cruz formation (now considered as mainly of mid-Miocene date) was the piece of a mandible which F. Ameghino described in 1887 as that of an edentate mammal, under the name of Phorysrhacos longissimus (Bolet. Mus. de la Plata, i. 24). In 1891 (Rev. Argent. Hist. Nat. i. 225) he amended the name and recognized the bone as that of a bird, Phororhacos, which with Brontornis and others constituted the family Phororhacidae. About six species of the type genus are now known, the most complete being Ph. inflatus, with skull, mandible, pelvis, limbs and some of the vertebrae. These birds were at first considered as either belonging to the Ratitae, or at least related to them, until C. W. Andrews, after much of the interesting material had been acquired by the British Museum, showed the gruiform affinities of Phororhacos (Ibis, 1896, pp. 1–12), a conclusion which he was able to further corroborate after the clearing of the adherent stony matrix from the skulls (Tr. Z. S. 1901, xv. pp. 55–86, pls. 14–17). The skull of Ph. longissimus is about 2 ft. long and 10 in. high; that of Ph. inflatus is 13 in. long, and this creature is supposed to have stood only 3 ft. high at the middle of the back. The under jaw is slightly curved upwards and it contains a large foramen as for instance in Psophia and in Mycteria. The strongly hooked upper beak is very high, and very much compressed laterally. The palate is imperfectly desmognathous, as in Dicholophus, with an inconspicuous vomer. The quadrate has a double knob for its articulation with the skull, and basipterygoid processes are absent. What l1ttle is known of the shoulder-girdle (breastbone still unknown) points to a flightless bird, and so do the short wing bones, although these are stout. The pelvis has an ischiadic foramen. The hind limbs are distinctly slender, the tibia of Ph. inflatus being between 15 and 16 in. in length.
|(From life-size model in Brit. Mus. Nat. Hist.)|
|Skull of Phororhacos, longissimus.|
For further detail see F. Ameghino, “Sur les oiseaux fossiles de la Patagonie,” Bolet. inst. geogr. argentino, xv., chs. 11 and 12 (1895); F. P. Moreno and A. Mercerat, Catálogo de los pájaros fósiles de la República Argentina, An. Mus. La Plata (1891; with 21 plates). (H. F. G.)