Loxornis Ameghino
Loxornis Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 595.
Another group of bones, which we found with considerable frequency, have the same features as Pelecyornis of the Santa Cruz. Ameghino has described but the lower end of a tibio-tarsus which can be associated with these bones and to it gave the name Loxornis. I can not find much variation from Pelecyornis except that the coracoid is considerably shorter and wider, and there is a slight variation in the lower end of the tibio-tarsus. These then are the bases of the generic name.
Loxornis clivus Ameghino
L. clivus Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 595.
Under this name Ameghino has described the lower end of a tibio-tarsus, a figure of which I reproduce here. This is of a size to complete the tibio-tarsus which we found, lacking the lower end, and agrees in size with the other bones which we found, so that I shall describe my material under this name. The species is in size comparable to Pelecyornis tubulatus with which it agrees closely.
Fig. 152. Humerus—
½ natural size.
Fig. 153. Sternum,
thin parts lacking—
½ natural size.
Fig. 154. Coracoid—
½ natural size.
We found the upper four-fifths of a tibio-tarsus, associated with part of the fibula, the sternum, the humerus, and the coracoid; a second specimen consisting of a complete tarso-metatarsus, and fragments of the pelvis, vertebrae and wing bones; a third specimen consisting of part of the tibio-tarsus, and various fragments; a fourth consisting of a femur, and lastly two toes; all evidently representing one species, which in most respects is almost identical with Pelecyornis tubulatus. These all came from the Chico del Chubut, west of Puerto Visser.
The humerus has a large head but is considerably flattened at the proximal end. The internal side is deeply excavated, the shaft is slender and light as though the wing were quite reduced, though not so much as in Pelecyornis and not nearly as much as in Phororhacus.
The sternum had a moderate keel but both this and body of the bone are very thin, so much so, that in my specimen, much is broken away, giving the figure the appearance of the bone being fenestrated, which was not the case. In general the sternum is similar to Pelecyornis.
The coracoid is a decidedly stout bone, with a wide distal end for articulation of the sternum. The proximal end has a long articular facet for the scapula. This bone is heavier than the corresponding one in Pelecyornis.
The femur has a small rounded head on a short neck, the articular surface spreading over the entire proximal end of the bone. Thus the trochanter is abbreviated and does not rise above the top of the head. The shaft is of considerable length and fairly heavy.
The tibio-tarsus has a wide flaring end to receive the articulation of the femur. The bone is very long as in Pelecyornis. On the external side is a long ridge along which the fibula was attached by cartilage or by ligaments, but was not fused to the tibio-tarsus. The shaft is approximately cylindrical in section and fairly heavy. The distal end is missing, but if I have associated correctly the specimen figured by Ameghino, the condyles are flattened, the inner being the flatter, and the outer rising in a narrow margin.
[Figure 157] shows a fibula which would have occupied the position indicated along the side of the tibio-tarsus and corresponds entirely with the same bone in Pelecyornis.
The tarso-metatarsus is long and slender, almost exactly the counterpart of the same bone in Pelecyornis. The bone has a triangular upper end, with two shallow articular concavities, separated by a median spine. The shaft is rectangular in cross section, has a shallow depression on the anterior face extending from the upper end to below the middle of the shaft; while on the posterior surface is a similar furrow, which is however bounded by a higher ridge on the external margin. The distal articular condyles are almost bilaterally symmetrical, the middle one being about half again as large as the two lateral ones. Just above the cleft between the condyles for digits III and IV there is a moderate sized perforation.
Fig. 155. Femur—
½ natural size.
Fig. 156. Tibio-tarsus—
½ natural size;
fibula indicated
in outline.
Fig. 157. Fibula—
½ natural size;
outline from
impression
in matrix.
Fig. 158. Tarso-metatarsus,
front view—
½ natural size.
Of the phalanges, I have two unguals which are narrow curved claws. These were not found in association with any of the foregoing bones, but correspond in size and general character to those of Pelecyornis, and so I consider them as belonging to this genus and species.
Fig. 159. Ungual phalanx—
½ natural size.
Fig. 160. Femur of
unknown bird—
natural size;
special No. 3217.
Ameghino has suggested that the genus was related to ducks, but with the more complete material it seems, in general build, much closer to the aberrant land birds of the Tertiary of South America, Pelecyornis and Phororhacus; and I am not in position to say what their derivation may have been.
Beside the above species there are several more or less complete but isolated bones indicating the presence of other and much smaller birds. I figure such a femur natural size.
Footnotes:
[1] Anal. Mus. Nac. Buenos Aires, ser. 3, t. 8, p. 99.
[2] Bul. Soc. Geol. France, ser. 4, t. 3, 1903, p. 468.
[3] Formations Sedimentaires, p. 498, Anal. Mus. Nac. Buenos Aires, ser. 3, t. 8.
[4] Neues Jarhbuch fur Mineralogie. bd. 21, p. 193.
[5] Princeton Expeditions Reports, vol. 4, p. 303.
[6] Princeton Expeditions to Patagonia, vol. 3, p. 310, 1905-11.
[7] History of Mammals, p. 127, 1896.
[8] Archhelenis and Archinotis, p. 125-145, 1907.
[9] Proc. Amer. Philos. Soc. Philadelphia, vol. 41, p. 350, 1902.
[10] See Scharff, Distribution and Origin of Life in America, Ch. 11, 1912.
[11] The following references discuss in detail the arrangement of these forms. Ameghino, 1906, Formations Sedimentaires, Anal. Museo Nac. de Buenos Aires, ser. 3, t. 8, p. 287-498: Roth, Los Ungulados Sudamericanos, Anal. Mus. La Plata, t. 5, 1903, p. 1-36: Scott, Princeton Patagonian Expeditions, vol. 6, p. 287-299, 1912: Gregory, Bul. Amer. Mus. Nat. Hist., vol. 27, p. 273-285, 1910.
[12] Princeton Expeditions Reports, Vol. VI, p. 7, 1909.
[13] P. crassus has been described, (loc. cit., p. 425,) based on pm. 2 and 3, of larger size than either of the foregoing but I do not think that the genus can be determined on so small a fragment.
[14] I have abandoned the family term Notohippidae, as the genus used as a basis is very little known, and the forms Ameghino assigns to the family, to my mind, mostly belong with the Nesodontidae.
[15] Scott has restored the head of Leontinia gaudryi with a single median horn, but no specimen in my collection would indicate anything but a pair of nasal horns. See Scott, Mammals of the Western Hemisphere, fig. 138, 1912.
[16] Annales Palaeontologie, 1906, t. 1, p. 28.
[17] Anal. Palaeontologie, t. 1, p. 5, 1906.
[18] Bol. Inst. Geog. Argen., t. 18, p. 442, fig. 25, 1897.
[19] Bul. Soc. Geol. France, ser. 4, t. 5, p. 305, 1905.
[20] I have a lower jaw of Propolymastodon which, though not complete in front, gives me no suggestion that the incisor was rodent-like, and I am inclined to think that the incisor associated with the type of P. carlo-zitelli is a mistake.
[21] Osborn, Bul. Amer. Mus. Nat. Hist., Vol. 24, p. 265.
[22] Bol. Inst. Geog. Argen., t. 18, p. 508, 1897.
[23] Bol. Acad. Nac. Cienc. Cordoba, t. 17, p. 56-66, 1902, no figures.
[24] There is a discussion as to the homologies of the premolars of marsupials and placental mammals, the one proposition being that marsupials have three premolars and four molars, the other that they have four premolars and three molars as in placentals. The evidence is not conclusive as to either proposition, but in this paper I have designated these teeth along the latter line of thought.
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