phylogenetic relationships and classification of didelphid marsupials ...

2009 VOSS AND JANSA: DIDELPHID MARSUPIALS 137
contact on lateral braincase (no frontalsquamosal
contact). Sagittal crest absent.
Petrosal consistently exposed laterally through
fenestra in parietal-squamosal suture in most
species (fenestra polymorphically absent in
M. incanus and M. noctivagus). Parietalmastoid
contact present (interparietal does
not contact squamosal).
Maxillopalatine fenestrae present; palatine
fenestrae present in some species (e.g., M.
creightoni; fig. 52), but absent in others (e.g.,
M. pinheiroi; fig. 53); maxillary fenestrae
absent; posterolateral palatal foramina small,
not extending anteriorly lingual to M4
protocones; posterior palatal morphology
conforms to Didelphis morphotype (with
prominent lateral corners, the choanae constricted
behind). Maxillary and alisphenoid
not in contact on floor of orbit (separated by
palatine). Transverse canal foramen present.
Alisphenoid tympanic process small, often
bluntly conical or laterally compressed (never
smoothly globular), always with a welldeveloped
anteromedial process enclosing
the extracranial course of mandibular nerve
(secondary foramen ovale present), and not
contacting rostral tympanic process of petrosal.
Anterior limb of ectotympanic directly
suspended from basicranium. Stapes triangular,
with large obturator foramen. Fenestra
cochleae exposed, not concealed by rostral
and caudal tympanic processes of petrosal.
Paroccipital process small, rounded, and
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 acute and strongly inflected.
Unworn crowns of I2–I5 symmetrically
rhomboidal (‘‘premolariform’’), with subequal
anterior and posterior cutting edges,
increasing in length (mesiodistal dimension)
from I2 to I5. Upper canine (C1) alveolus in
premaxillary-maxillary suture; C1 without
accessory cusps in some species (e.g., M.
creightoni; fig. 52), or with posterior accessory
cusp (e.g., M. juninensis), or with anterior
and posterior accessory cusps (e.g., M.
pinheiroi; fig 53). First upper premolar (P1)
smaller than posterior premolars but well
formed and not vestigial; second and third
upper premolars (P2 and P3) subequal in
height; P3 with posterior cutting edge only;
upper milk premolar (dP3) large and molariform.
Molars strongly carnassialized (postmetacristae
much longer than postprotocristae);
relative widths usually M1 , M2 , M3
, M4; centrocrista strongly inflected labially
on M1–M3; ectoflexus shallow or indistinct
on M1, shallow but usually distinct on M2,
and consistently deep on M3; anterolabial
cingulum and preprotocrista discontinuous
(anterior cingulum incomplete) on M3 in
some species (e.g., M. noctivagus) but anterolabial
cingulum continuous with preprotocrista
(anterior cingulum complete) in
others (e.g., M. parvidens); postprotocrista
without carnassial notch. Last upper tooth to
erupt is P3.
Lower incisors (i1–i4) with distinct lingual
cusps. Second lower premolar (p2) subequal
in height to p3 in some species (e.g., M.
incanus) but distinctly taller than p3 in others
(e.g., M. impavidus); lower milk premolar
(dp3) trigonid complete. Hypoconid labially
salient on m3; hypoconulid twinned with
entoconid on m1–m3; entoconid usually
taller than hypoconulid on m1–m3.
DISTRIBUTION: Species of Marmosops occur
in tropical lowland and montane moist
forests from central Panama southward
along the Andes and throughout Amazonia
to eastern Bolivia and southeastern Brazil
(see maps in Gardner and Creighton, 2008a).
The genus is apparently unknown from
Paraguay, Argentina, and Uruguay. See
Mustrangi and Patton (1997) for verified
specimen records based on modern revisionary
research in southeastern Brazil, Patton et
al. (2000) for the same in western Amazonia,
Voss et al. (2001) for northeastern Amazonia,
and Voss et al. (2004b) for Bolivia. Many
other published geographic data purporting
to represent records of Marmosops species
(e.g., Anderson, 1997; Brown, 2004) are
based on misidentified material (Voss et al.,
2004b).
REMARKS: The monophyly of Marmosops
is uniformly strongly supported by parsimony,
likelihood, and Bayesian analyses of
IRBP (fig. 28), DMP1 (fig. 29), BRCA1
(fig. 31), vWF (fig. 32), and concatenated
sequence data from five genes (fig. 33). The
genus is also recovered with strong support
by parsimony and Bayesian analyses of