PDF (Lo-Res) - Smithsonian Institution Libraries

NUMBER 89 181
FIGURE 5.—Vulturidae, probably a new genus and species (MLP 90-X-l-l).
Proximal end of radius: a, anconal view; b, palmar view. Proximal end of ulna
and shaft: c, external view; d, palmar view; e, anconal view. Scale bar=l cm.
lis, 61; width of midshaft, 20.8; depth of midshaft, 16.3; distal
width, 46.9.
REMARKS.—Before now, Geronogyps was known only from
the Pleistocene sediments of the Talara Tar Seeps, Peru (Campbell,
1979). Campbell established this genus based on a complete
tarsometatarsus, with the distal end of a left humerus and
the proximal and distal ends of two right humeri as paratypes.
Because the paratypes are badly crushed, the specimens reported
herein bring additional information about the morphology of
Geronogyps reliquus.
The following characters of Geronogyps reliquus, given by
Campbell (1979), are present in the Argentinian specimen: (1)
margo caudalis dropping off sharply on both sides, whereas
more rounded in Vultur and Gymnogyps; (2) attachment of M.
proscapulohumeralis brevis more proximal than in Vultur; (3)
crista deltopectoralis flaring distally, not flaring as much in
Vultur or in Gymnogyps; (4) shaft ventral to M. pectoralis superficialis
not depressed, unlike Vultur and similar to Gymnogyps;
(5) condylus dorsalis wide and short, whereas narrow
and long in Vultur and Gymnogyps; (6) condylus ventralis
short (very long in Vultur and moderately long in Gymnogyps);
(7) epicondylus dorsalis long and not angular, unlike
Vultur; (8) condylus ventralis gently rotated anteriad, resulting
in moderately flexed distal end, as in Gymnogyps (greatly
rotated in Vultur); and (9) impression of M. brachialis shallower
than in Vultur or Gymnogyps.
Discussion and Conclusions
Condors, one of the primary scavenging lineages of birds,
are large-sized vulturids with past and present distributions
restricted to the New World. The fact that the temporal range
of condors is less extensive in South America (middle-late
Pliocene) than in North America (middle Miocene), and that
their absence from the richly fossiliferous Paleogene and early
Neogene outcroppings of Argentina does not seem to be
related to taphonomic problems, could probably be considered
a reaffirmance of Emslie's idea (1988a) about a North
American origin for the group. Condors may have participated
in the Great American Biotic Interchange (GABI) during
Pliocene times (Webb and Marshall, 1982; Emslie, 1988a),
moving from north to south across open savanna environments;
however, the presence of a fossil condor, Antillovultur
varonai Arredondo (1971), from the late Pleistocene of Cuba,
proves that condors can cross water barriers. This fact, together
with the evidence of a significant interchange of pre-
Pliocene volant bird families between both Americas before
the formation of a land connection (Rasmussen and Kay,
1992), seems to weaken the hypothesis that condors were
part of the latest events of the GABI. Our analysis does not
make it possible to bring arguments in favor of, or against,
this hypothesis.
The fossil record summarized above indicates that a great diversity
of condors occurred in the late Cenozoic of the Pampean
region of Argentina, including three genera and at least
four species: Dryornis pampeanus, Vultur gryphus, Gerono-