1911 Encyclopædia Britannica/Odontornithes
ODONTORNITHES, the term proposed by O. C. Marsh (Am. Journ. Sci. ser 3, v. (1873) pp. 161–162) for birds possessed of teeth (Gr. ὀδούς, tooth, ὄρνις, ὄρνιθος, bird), notably the genera Hesperornis and Ichthyornis from the Cretaceous deposits of Kansas. In 1875 (op. cit. x. pp. 403–408) he divided the “subclass” into Odontolcae, with the teeth standing in grooves, and Odontotormae, with the teeth in separate alveoles or sockets. In his magnificent work, Odontornithes: A monograph on the extinct toothed birds of North America, New Haven, Connecticut, 1880, he logically added the Saururae, represented by Archacopteryx, as a third order. As it usually happens with the selection of a single anatomical character, the resulting classification was unnatural. In the present case the Odontornithes are a heterogeneous assembly, and the fact of their possessing teeth proves nothing but that birds, possibly all of them, still had these organs during the Cretaceous epoch. This, by itself, is a very interesting point, showing that birds, as a class, are the descendants of well-toothed reptiles, to the complete exclusion of the Chelonia with which various authors persistently try to connect them. No fossil birds of later than Cretaceous age are known to have teeth, and concerning recent birds they possess not even embryonic vestiges.
E. Geoffroy St Hilaire stated in 1821 (Ann. Gén. Sci. Phys. viii. pp. 373–380) that he had found a considerable number of tooth-germs in the upper and lower jaws of the parrot Palaeornis torquatus. E. Blanchard (“Observations sur le système dentaire chez les oiseaux,” Comptes rendus 50, 1860, pp. 540–542) felt justified in recognizing flakes of dentine. However, M. Braun (Arbeit Zool. Inst., Würzburg, v. 1879) and especially P. Fraisse (Phys. Med. Ges., Würzburg, 1880) have shown that the structures in question are of the same kind as the well-known serrated “teeth” of the bill of anserine birds. In fact the papillae observed in the embryonic birds are the soft cutaneous extensions into the surrounding horny sheath of the bill, comparable to the well-known nutritive papillae in a horse’s hoof. They are easily exposed in the well-macerated under jaw of a parrot, after removal of the horny sheath. Occasionally calcification occurs in or around these papillae, as it does regularly in the “egg-tooth” of the embryos of all birds.
The best known of the Odonlornithes are Hesperornis regalis, standing about 3 ft. high, and the somewhat taller H. crassipes. Both show the general configuration of a diver, but it is only by analogy that Hesperornis can be looked upon as ancestral to the Colymbiformes. There are about fourteen teeth in a groove of the maxilla and about twenty-one in the mandible; the vertebrae are typically heterocoelous; of the wing-bones only the very slender and long humerus is known; clavicles slightly reduced; coracoids short and broad, movably connected with the scapula; sternum very long, broad and quite Hat, without the trace of a keel. Hind limbs very strong and of the Colynibine type, but the outer or fourth capitulum of the metatarsus is the strongest and longest, an unique arrangement in an otherwise typically steganopodous foot. The pelvis shows much resemblance to that of the divers, but there is still an incisura ischiadica instead of a foramen. The tail is composed of about twelve vertebrae, without a pygostyle. Enaliornis of the Cambridge Greensand of England, and Baptornis of the mid-Cretaceous of North America, are probably allied, but imperfectly known. The vertebrae are biconcave, with heterocoelous indications in the cervical; the metatarsal bones appear still somewhat imperfectly anchylosed. The absence of a keel misled Marsh who suspected relationship of Hesperornis with the Ratitae, and L. Dollo went so far as to call it a carnivorous, aquatic ostrich (Bull. Sci. Départ. du Nord, ser. 2, iv. 1881, p. 300), and this mistaken notion of the " swimming ostrich " was popularized by various authors. B. Vetter (Festschr. Ges. Isis., Dresden, 1885) rightly pointed out that Hesperornis was a descendant of Carinatae, but adapted to aquatic life, implying reduction of the keel. Lastly, M. Fürbringer (Untersuchungen, Amsterdam, 1888, pp. 1543, 1505, 1580) relegated it, together with Enaliornis and the Colymbo-Podicipedes, to his suborder Podicipitiformes. The present writer does not feel justified in going so far. On account of their various, decidedly primitive characters, he prefers to look upon the Odontolcae as a separate group, one of the three divisions of the Neornithes, as birds which form an early offshoot from the later Colymbo-Pelargomorphous stock; in adaptation to a marine, swimming life they have lost the power of flight, as is shown by the absence of the keel and by the great reduction of the wing-skeleton, just as in another direction, away from the later Alectoromorphous stock the Ratitae have specialized as runners. It is only in so far as the loss of flight is correlated with the absence of the keel that the Odontolcae and the Ratitae bear analogy to each other.
There remain the Odontotormae, notably Ichthyornis victor, I. dispar, Apatornis and Graculavus of the middle and upper Cretaceous of Kansas. The teeth stand in separate alveoles; the two halves of the mandible are, as in Hesperornis, without a symphysis. The vertebrae are amphicoelous, but at least the third cervical has somewhat saddle-shaped articular facets. Tail composed of five free vertebrae, followed by a rather small pygostyle. Shoulder girdle and sternum well developed and of the typical carinate type. Pelvis still with incisura ischiadica. Marsh based the restoration of Ichthyornis, which was obviously a well-flying aquatic bird, upon the skeleton of a tern, a relationship which cannot be supported. The teeth, vertebrae, pelvis and the small brain are all so many low characters that the Odontotormae may well form a separate, and very low, order of the typical Carinatae, of course near the Colymbomorphous Legion. (H. F. G.)