phylogenetic relationships and classification of didelphid marsupials ...

126 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 322
elsewhere in northern Argentina, eastern
Bolivia, western Paraguay, and southwestern
Brazil, it would be reasonable to expect that
the genus is more widely distributed.
REMARKS: In the absence of undamaged
cranial material, we are unable to provide an
illustration for this genus. However, photographs
of two imperfect skulls were published
by Voss et al. (2004a: fig. 2) and Teta et al.
(2006: fig. 2).
The problematic relationships of this genus
were discussed at length by Voss et al.
(2004a) and seem unlikely to be resolved
definitively in the absence of nuclear gene
sequence data. As discussed above, the tribal
membership of Chacodelphys is most compellingly
supported by Bayesian analysis of a
dataset that combines nonmolecular characters
with nuclear-gene sequence data (fig. 36),
but it is consistent with subjective assessments
of similarity based on integumental
and craniodental traits (e.g., by Tate, 1933).
Although separate analyses of nonmolecular
character data suggest that this genus may
be more closely related to Thylamys and
Lestodelphys than to other thylamyines (fig.
27), it seems premature to formalize such
weakly supported results by subtribal nomenclature.
Cryptonanus Voss et al., 2005
Figure 49
CONTENTS: agricolai Moojen, 1943; chacoensis
Tate, 1931; guahybae Tate, 1931;
ignitus Díaz et al., 2002; and unduaviensis
Tate, 1931.
MORPHOLOGICAL DESCRIPTION: Combined
length of adult head and body ca. 80–
120 mm; adult weight ca. 15–40 g. Ventral
margin of rhinarium with two shallow
grooves on each side of median sulcus; dark
circumocular mask present; pale supraocular
spot absent; dark midrostral stripe absent;
gular gland present in adult males. Dorsal
body pelage unpatterned, usually grayish or
reddish brown; dorsal fur gray based; dorsal
guard hairs very short and inconspicuous;
ventral fur gray based or self-colored (varying
among species). Manus paraxonic (dIII 5
dIV); manual claws shorter than fleshy apical
pads of digits; dermatoglyph-bearing manual
plantar pads present; central palmar surface
of manus sparsely tubercular (neither smooth
nor densely covered with convex tubercles);
lateral carpal tubercles present in adult males.
Pedal digits unwebbed; dIV longer than other
pedal digits; plantar epithelium of heel
naked. Pouch absent; mammae 4–1–4 5 9
(all abdominal-inguinal) to 7–1–7 5 15 (with
pectoral teats); cloaca present. Tail longer
than combined length of head and body,
slender and muscular (not incrassate); body
pelage not extending more than a few mm
onto tail base; unfurred caudal integument
more or less bicolored (dark above, paler
below) in most specimens; caudal scales in
distinctly annular series, each scale with three
subequal bristlelike hairs emerging from
distal margin; ventral caudal surface modified
for prehension distally, with apical pad
bearing dermatoglyphs.
Rostral process of premaxillae absent.
Nasals long, extending anteriorly beyond I1
(concealing nasal orifice from dorsal view),
and conspicuously widened posteriorly near
maxillary-frontal suture. Maxillary turbinals
large and elaborately branched. Two lacrimal
foramina laterally exposed on each side on or
just anterior to orbital margin. Supraorbital
margins rounded, without beads or processes
(a few old individuals have incipient postorbital
processes); distinct interorbital and
postorbital constrictions usually present in
juveniles and young adults. Left and right
frontals and parietals separated by persistent
median sutures. Parietal and alisphenoid in
contact on lateral braincase (no squamosalfrontal
contact). Sagittal crest absent. Petrosal
laterally exposed through fenestra in
parietal-squamosal suture. Parietal-mastoid
contact present (interparietal does not contact
squamosal).
Maxillopalatine fenestrae large; palatine
fenestrae present; maxillary fenestrae absent;
posterolateral palatal foramina small, not
extending lingual to M4 protocones; posterior
palate conforms to Didelphis morphotype
(with prominent lateral corners, the internal
choanae abruptly constricted behind). Maxillary
and alisphenoid not in contact on
orbital floor (separated by palatine). Transverse
canal foramen present. Alisphenoid
tympanic process smoothly globular, without
anteromedial process or posteromedial lamina
enclosing extracranial course of mandib-