Late Cenozoic Land Mammals from Grenada, Lesser Antilles Island ...

2 AMERICAN MUSEUM NOVITATES
NO. 3302
sibly introduced by human agency (Varona,
1974; Eisenberg, 1989). At the species level,
no Grenadian mammal is an exclusive endemic,
4 a fact that has been used (e.g., by
Groome, 1970) to argue that this island was
never connected to South America (but see
Discussion and Conclusions). Until the recent
discovery of two unnamed species of
oryzomyin sigmodontines in very late Qua-
4
An exclusive endemic is a species-level taxon that
originated in, and whose primary natural distribution is
limited to, a single continuous area (usually small). In
principle, origin could be allopatric or sympatric, although
for obvious reasons allopatric endemics are easier
to document. Endemics can, of course, secondarily
disperse, but by definition they remain endemic in their
area of origin until and unless extinction occurs therein.
Island endemics are exclusive only when sufficiently differentiated
from mainland parent populations/species (
allopatry). Until there is differentiation there is no exclusive
endemism, only range extension.
ternary contexts (Pregill et al., 1994), no extinct
land mammals of any sort were known
from Grenada.
This report adds two more entries to the
Grenadian faunal list: Hydrochaeris gaylordi,
new species, and Megalonychidae, gen. &
sp. indet., material of which was recovered
by one of us (RS) from a lahar deposit on
the south end of the island. The capybara,
represented by a partial maxillary dentition,
is similar but not identical to living Hydrochaeris
hydrochaeris from the South American
mainland. The sloth material is scanty:
little can be said about it beyond the fact that
the specimens are megalonychid. A few fragments
of bone belonging to smaller vertebrates
(?lizards) were found in matrix samples,
but none is complete enough to identify.
Whatever their limitations as specimens,
these finds are important because they pro-