phylogenetic relationships and classification of didelphid marsupials ...

94 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 322
Maxillopalatine fenestrae usually absent
(small fenestrae, never extending anteriorly
beyond M1 or posteriorly beyond M2, are
uni- or bilaterally present in occasional
specimens); palatine and maxillary fenestrae
absent; posterolateral palatal foramina small,
not extending anteriorly between M4 protocones;
posterior palate gently sloping ventrally,
usually with arched caudal margin and
without prominent posterolateral corners
(the choanae unconstricted behind). Maxillary
and alisphenoid not in contact on floor
of orbit (separated by palatine). Transverse
canal foramen absent. Alisphenoid tympanic
process more or less conical (acutely pointed
ventrally), usually without posteromedial
lamina enclosing extracranial course of mandibular
nerve (secondary foramen ovale
absent), 24 and contacting or closely approximating
rostral tympanic process of petrosal.
Anterior limb of ectotympanic indirectly
suspended from basicranium (by malleus).
Stapes triangular with large obturator foramen
(in subgenus Caluromys) or subtriangular
with small but patent foramen (in
subgenus Mallodelphys). Fenestra cochleae
concealed in sinus formed by rostral and
caudal tympanic processes of petrosal. Paroccipital
process small, rounded and subtriangular,
adnate to petrosal. Dorsal margin
of foramen magnum bordered by supraoccipital
and exoccipitals, incisura occipitalis
present.
Two mental foramina usually present on
lateral surface of each hemimandible; angular
process blunt and weakly inflected.
Unworn crowns of I2–I5 asymmetrical
(‘‘incisiform’’), with much longer anterior
than posterior cutting edges. Upper canine
(C1) alveolus contained entirely in maxillary
bone; C1 simple, without accessory cusps.
First upper premolar (P1) minute, vestigial,
and lacking any consistent occlusal features;
second upper premolar (P2) much taller than
P3; P3 with both anterior and posterior
cutting edges; upper milk premolar (dP3)
large and molariform. Molars not carnassialized
(postprotocristae and postmetacristae
are subequal in subgenus Mallodelphys) or
weakly carnassialized (postmetacristae are
24 We examined one old adult male (MVZ 190249) with a
secondary foramen ovale formed by a posteromedial lamina.
slightly longer than postprotocristae in subgenus
Caluromys); relative widths usually M1
, M2 . M3 . M4 (subgenus Mallodelphys)
or M1 , M2 , M3 . M4 (subgenus
Caluromys); centrocrista weakly inflected
labially on M1–M3; ectoflexus consistently
absent on all upper molars; anterolabial
cingulum continuous with preprotocrista
(complete anterior cingulum present) on
M3; postprotocrista without carnassial
notch. Last upper tooth to erupt is P3.
Lower incisors (i1–i4) with distinct lingual
cusps. Lower canine (c1) erect, acutely
pointed, and simple (without a posterior
accessory cusp). Second upper premolar
(p2) much taller than p3; lower milk premolar
(dp3) trigonid with or without paraconid
(when present, the paraconid is small and
often indistinct). Hypoconid labially salient
on m3; hypoconulid twinned with entoconid
on m1–m3; entoconid much taller than
hypoconulid on m1–m3.
DISTRIBUTION: Caluromys occurs from the
Mexican state of Veracruz southward
throughout most of the forested regions of
Central and South America (including Trinidad)
to eastern Bolivia, eastern Paraguay,
and northeastern Argentina (Hall, 1981;
Gardner, 2008). Most specimens of C. lanatus
and C. philander (e.g., those reported by
Handley, 1976; Anderson, 1997) are from
lowland or lower montane rainforest; however,
C. philander has also been observed in
dry forest (Emmons, 1998), and C. derbianus
ranges from sea level to over 2000 m and
occurs in both rainforest and dry forest
(Handley, 1966; Bucher and Hoffmann,
1980; Sánchez et al., 2004).
REMARKS: Generic monophyly (vis-à-vis
Caluromysiops) is supported by IRBP sequence
data (fig. 28), by the presence of a
distinct midrostral stripe, and by the presence
of a small but distinct rostral process of the
premaxillae (the latter two traits optimize as
unambiguous generic synapomorphies; appendix
5).
The genus Caluromys has never been
revised, and there is substantial divergence
in morphology and/or cytochrome b sequences
among some allegedly conspecific populations
(Voss et al., 2001; Patton and Costa,
2003). Indeed, no revisionary study has
documented the conspecific status of the