PDF (Lo-Res) - Smithsonian Institution Libraries

A New Genus for the Incredible Teratorn
(Aves: Teratornithidae)
ABSTRACT
A partial humerus of a giant flying bird from Blancan (upper
Pliocene) deposits of California is determined to be a teratorn,
although the humerus differs from those of other known genera of
the family Teratornithidae in the position of the attachment of the
M. latissimus dorsi and in the shape of the humeral shaft. The new
specimen is referred to the Incredible Teratorn, Teratornis incredibilis
Howard (1952), and a reexamination of all the specimens previously
referred to this taxon reveals sufficient grounds to erect a
new genus for this species. The size of the new partial humerus
suggests that the bird had a wingspan of approximately 5 m, which
is the same estimate previously given for the Incredible Teratorn.
Introduction
Teratorns are members of an extinct family of giant flying
birds, the Teratornithidae (Miller, 1925), which currently is
placed within the order Ciconiiformes (Jollie, 1976-1977; Rea,
1983; Olson, 1985; Emslie, 1988). Three genera have been recognized
in the family: Teratornis L. Miller (1909), Cathartornis
L. Miller (1910), and Argentavis Campbell and Tonni
(1980). One species has been assigned to each of the latter two
genera, whereas two species have been assigned to Teratornis:
T. merriami L. Miller (1910) and T. incredibilis Howard
(1952). Teratorns were the largest flying birds known, with the
largest, Argentavis magnificens Campbell and Tonni (1980),
reaching a wingspan of 6-8 m and a weight of 72-79 kg
(Campbell and Tonni, 1980; Campbell and Marcus, 1992). Our
current understanding of teratorns has been summarized by
Campbell and Tonni (1980, 1982, 1983) and Campbell (1995).
Kenneth E. Campbell, Jr., Natural History Museum of Los Angeles
County, 900 Exposition Boulevard, Los Angeles, California 90007,
United States. Eric Scott and Kathleen B. Springer, San Bernardino
County Museum, 2024 Orange Tree Lane, Redlands, California
92374, United States.
Kenneth E. Campbell, Jr., Eric Scott,
and Kathleen B. Springer
169
The discovery of a partial humerus of a teratorn of a size
similar to that estimated for Teratornis incredibilis allows us to
clarify the status of that species, to which five specimens of
widely different ages (late Pliocene to late Pleistocene) have
previously been referred. The holotype of the species, an os
carpi ulnare (cuneiform) (Howard, 1952), is the most diagnostic
specimen, whereas the four referred specimens are much
less so. Although these specimens, namely, the proximal end of
an ulna, the distal end of a radius, the fragmentary proximal
end of a carpometacarpus, and the anterior portion of a beak,
were not very diagnostic, they were identified as teratorns and
were referred to T. incredibilis primarily on the basis of size
(Howard, 1963, 1972; Emslie, 1995; Jefferson, 1995). A sixth
specimen, the fragmentary distal end of a right carpometacarpus
recently discovered in upper Pliocene deposits of central
Mexico and described below, is assigned herein to this species.
A seventh specimen, a vertebra, previously referred to T. incredibilis
(Heaton, 1984) was later reassigned to T. merriami
(Emslie and Heaton, 1987). This specimen was not seen by us.
In spite of being rather fragmentary, the new specimen clearly
possesses characters that unite it with the teratorns. At the
same time, other characters clearly distinguish it from humeri
of the genus Teratornis, which suggests that it represents a genus
distinct from Teratornis. We took the opportunity this
specimen provided to reexamine all specimens referred to T.
incredibilis, and we found grounds for placing all of them in a
new genus.
Osteological terminology is from Baumel (1993) and
Howard (1980).
ACKNOWLEDGMENTS.—Fossil mammals from Murrieta
were identified by R.L. Reynolds, San Bernardino County Museum;
additional identifications were provided by CA. Repenning,
United States Geological Survey. Paleontologie Resource
Assessment Program (PRAP) mitigation was conducted in cooperation
with H. Meyers of the Kulberg Group, Temecula. We
thank R. Chandler, Georgia College and State University, and
O. Carranza-Castaneda, Instituto de Geologia, Universidad Na-