BIRDS
In the Deseado beds, birds occur in small numbers, Ameghino having
described four species. The remains are generally found as isolated
bones, and it is hard to associate the separate finds one with another.
Beside this there are very few birds of the early Tertiary so known, as
to make separate bones indicate the family or generic relationships.
In the overlying Patagonian beds, a considerable number of species
have been found, mostly of penguin-like birds, the various genera and
species being based on the tarso-metatarsus. On the upper surface of
the Deseado, we found several bones of this penguin-like type, but
in all cases they were washed out, so that I have considered them as
having come from the Patagonian.
However, we found eight specimens of birds in place in the Deseado,
most of which are clearly land birds and belong to genera which are
closely related to genera of the Santa Cruz, especially the two genera
_Phororhacus_ and _Pelecyornis_, and of sizes equal to the largest
representatives of the two genera.
=Phororhacus= Ameghino
Phororhacus Amegh., 1887, Bol. Mus. La Plata, t. 1, p. 24.
Phororhacus Amegh., 1889, Act. Acad. Nac. Cienc. Cordoba, t. VI, p. 659.
Phororhacus Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 10 of
separate.
This is a group of large land birds, comparable in size to the great
moas of New Zealand which apparently arose, flourished, and died out
in South America. In the Santa Cruz they were abundant, the best
known form being _P. inflatus_, a bird some six feet high; while the
largest, _P. longissimus_, had a head nearly twice as long and limb
bones half again as large as this species; so that it represented a
bird nine to ten feet high. Previously but one specimen of this type,
a part of a mandible, has been found in the Deseado beds. We were
fortunate enough to find the greater part of a femur, indicating a bird
equal to the largest of those in the Santa Cruz. There are also toe
bones of _Phororachus_ of a size about the same as _P. inflatus_.
A host of names, generic and specific, have been given to the
individual bones of the birds of this type, but Ameghino, in studying
the birds of the Santa Cruz, brought them all together under the single
genus _Phororhacus_. (See Bol. Inst. Geog. Argen., 1895, t. 15.)
Referring to the single bone in the Deseado, however, he gave it a new
generic name _Physornis_, which differs from _Phororhacus_ only in the
lower jaw being more convex, but should stand until better material has
been found to establish whether it differs enough to be entitled to
generic independence.
=Physornis fortis= Ameghino.
P. fortis Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 576.
Under this specific name Ameghino describes a part of the lower jaw
150 mm. long which he says equals in size _Phororhacus longissimus_,
and differs only in the greater convexity of the mandible. Our
specimen is a femur, apparently of the same bird, being of the type of
_Phororhacus_ and about the size of _P. longissimus_; so I have placed
it in this species.
This femur is of large size, moderate length, and has a shaft
subcylindrical in section. The distal end is expanded and the condyles
are flattened, the inner one being the wider, the outer condyle being
narrower and the external margin projecting to make a high ridge. The
pit on the posterior side of the shaft just above the condyles is
unusually deep and of large size. On the anterior side there extends
from either condyle a low marginal ridge which soon fades into the
contour of the shaft. Between these ridges there is a wide shallow
furrow which also loses itself above in the convex surface of the
shaft.
[Illustration: Fig. 149. Right femur, back view—½ natural size.]
MEASUREMENTS
Femur, least diam. of the shaft 58 mm.
Femur, diameter across the condyles 148 mm.
=Physornis= sp.?
Two phalanges of a size too small to belong to the above species
represent a second smaller bird of this type, about equal in size to
_Phororhacus inflatus_. I give a figure of one toe but would wait for
more typical material before establishing a species.
[Illustration: Fig. 150. Proximal phalanx of Physornis sp?—natural
size.]
[Illustration: Fig. 151. Loxornis clivus, lower end of tibio-tarsus,
after Ameghino—natural size.]
=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.
[Illustration: Fig. 152. Humerus—½ natural size.]
[Illustration: Fig. 153. Sternum, thin parts lacking—½ natural size.]
[Illustration: 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.
[Illustration: Fig. 155. Femur—½ natural size.]
[Illustration: Fig. 156. Tibio-tarsus—½ natural size; fibula indicated
in outline.]
[Illustration: Fig. 157. Fibula—½ natural size; outline from impression
in matrix.]
[Illustration: 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.
[Illustration: Fig. 159. Ungual phalanx—½ natural size.]
[Illustration: 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.