Didelphis Linnaeus, 1758

Voss, RS & Jansa, SA, 2009, Phylogenetic Relationships And Classification Of Didelphid Marsupials, An Extant Radiation Of New World Metatherian Mammals, Bulletin of the American Museum of Natural History 2009 (322), pp. 1-177 : 116-118

Didelphis Linnaeus, 1758 Figure 46

CONTENTS: albiventris Lund, 1840 (including bonariensis Marelli, 1930; dennleri Marelli, 1930; lechei Ihering, 1892; leucotis Wagner, 1847; paraguayensis J.A. Allen, 1902 ; poecilotis Wagner, 1842; and poecilonota Schinz, 1844); aurita Wied-Neuweid, 1826 (including koseritzi Ihering, 1892; longipilis Miranda-Ribeiro, 1935; and melanoidis Miranda-Ribeiro, 1935); imperfecta Mondolfi and Pérez-Hernández, 1984 ; marsupialis Linnaeus, 1758 (including battyi Thomas, 1902; cancrivora Gmelin, 1788; caucae J.A. Allen, 1900; colombica J.A. Allen, 1900; etensis J.A. Allen, 1902; insularis J.A. Allen, 1902; karkinophaga Zimmermann, 1780; particeps Goldman, 1917; richmondi J.A. Allen, 1901; and tabascensis J.A. Allen, 1901); pernigra J.A. Allen, 1900 (including andina J.A. Allen, 1902; and meridensis J.A. Allen, 1902); and virginiana Kerr, 1792 (including boreoamericana J.A. Allen, 1902; breviceps Bennett, 1833 ; californica Bennett, 1833; cozumelae Merriam, 1901; illinensium Link, 1795; pigra Bangs, 1898; pilosissima Link, 1795; pruinosa Wagner, 1843; texensis J.A. Allen, 1901; woapink Barton, 1806; and yucatanensis J.A. Allen, 1901).

MORPHOLOGICAL DESCRIPTION: Combined length of adult head and body 310–495 mm; adult weight 600–5100 g. Rhinarium with one ventrolateral groove on each side of median sulcus; dark circumocular mask indistinct in some species ( D. aurita , D. marsupialis , D. virginiana ) but distinct in others ( D. albiventris , D. imperfecta , D. pernigra ); pale supraocular spot absent; dark midrostral stripe absent; throat gland absent. Dorsal pelage unpatterned; dorsal underfur white; dorsal guard hairs long, coarse and conspicuous, giving the pelage a distinctively shaggy appearance; ventral fur pale (usually whitish) tipped with black. Manus mesaxonic (dIII. dIV); manual claws usually longer than fleshy apical pads of digits; dermato- glyph-bearing manual plantar pads present; central palmar epithelium smooth or sparsely tuberculate; carpal tubercles absent. Pedal digits unwebbed; dIV slightly longer than other pedal digits in some species (e.g., D. marsupialis ) or dII, dIII, and dIV subequal (e.g., in D. albiventris and D. virginiana ); plantar surface of heel naked. Pouch well developed, opening anteriorly; mammae normally 3–1–3 5 7 to 6–1–6 5 13 or more29; cloaca present. Tail slightly longer than combined length of head and body, slender and muscular (not incrassate); basal 1/6 to 1/4 densely furred (covered with body pelage); naked caudal integument blackish proximally and abruptly whitish distally; caudal scales in spiral series, each scale usually with three subequal bristlelike hairs emerging from distal margin; ventral caudal surface variably modified for prehension distally (prehensile modifications are more strongly developed in D. auritus and D. marsupialis than in the other species), but dermatoglyph-bearing apical pad consistently present.

Premaxillary rostral process absent. Nasals short, not produced anteriorly above I1 (exposing nasal orifice in dorsal view), and conspicuously widened posteriorly near maxillary-frontal suture. Maxillary turbinals elaborately branched. Lacrimal foramina one or two on each side, exposed laterally on orbital margin or on face just anterior to orbit. Postorbital processes bluntly pyramidal, maximally developed in old adults. Left and right frontals co-ossified (midfrontal suture incomplete or absent), but left and right parietals separated by persistent midparietal suture. Parietal and alisphenoid in contact on lateral braincase (no frontalsquamosal contact). Sagittal crest large, well developed, and extending onto frontals. Petrosal not exposed laterally through fenestra in squamosal-parietal suture (fenestra absent). Parietal-mastoid contact absent (interparietal narrowly contacts squamosal).

Maxillopalatine and palatine fenestrae present; maxillary fenestrae absent; posterolateral palatal foramina not extending anteriorly lingual to M4 protocones; posterior

29 Occasional records of Didelphis virginiana with up to 17 pouch young (cited by Hamilton, 1958) suggest that teat counts in this species may sometimes exceed 6–1–6 5 13.

palate with prominent lateral corners, the choanae abruptly constricted behind. Maxillary and alisphenoid not in contact (separat- ed by palatine) on floor of orbit. Transverse canal foramen present. Alisphenoid tympanic process small and uninflated, usually with posteromedial lamina enclosing extracranial course of mandibular nerve (secondary fora- men ovale usually present), and not in contact with rostral tympanic process of petrosal. Anterior limb of ectotympanic suspended indirectly from basicranium (by malleus). Stapes usually triangular with large obturator foramen but sometimes columellar and imperforate (varies within species). Fenestra cochleae exposed, not concealed by rostral and caudal tympanic processes of petrosal. Paroccipital process large, erect (not adnate to petrosal) and projecting ventrally. Dorsal margin of foramen magnum bordered by exoccipitals only, incisura occipitalis absent.

Two mental foramina usually present on lateral surface of each hemimandible (one foramen is present unilaterally in a single examined specimen of D. albiventris ); mandibular angular process acute and strongly inflected medially.

Unworn crowns of I2–I5 asymmetrical (‘‘incisiform’’), with much longer anterior than posterior cutting edges. Upper canine (C1) alveolus in premaxillary-maxillary suture; C1 simple, without accessory cusps. First upper premolar (P1) smaller than posterior premolars, but well-formed and not vestigial; third upper premolar (P3) taller than second (P2); P3 with posterior cutting edge only; upper milk premolar (dP3) large and molariform. Molars highly carnassialized (postmetacristae conspicuously longer than postprotocristae); relative widths M1, M2, M3. M4 or M3, M4; centrocrista only weakly inflected labially on M1–M3; ectoflexus shallow, indistinct, or absent on M1 and M2, but consistently deep and distinct on M3; anterolabial cingulum and preprotocrista discontinuous (anterior cingulum incomplete) on M3; postprotocrista with carnassial notch. Last upper tooth to erupt is M4.

Lower incisors (i1–i4) without distinct lingual cusps. Second lower premolar (p2) much taller than p3; lower milk premolar (dp3) with complete (tricuspid) trigonid. Hypoconid labially salient on m3; hypoconulid twinned with entoconid on m1–m3; entoconid much taller than hypoconulid on m1–m3.

DISTRIBUTION: Didelphis is a quintessentially eurytopic genus that ranges from southern Canada throughout most of North America (except the Rockies, the northern Great Plains, the Great Basin, the arid southwest, north-central Mexico, and Baja California; Hall, 1981), all of Central America, and most of South America (to about 40 ° S latitude in central Argentina; Flores et al., 2007). South American collection records (mapped by Cerqueira and Tribe, 2008) represent almost every non-desert tropical and subtropical biome on the continent.

REMARKS: Despite contradictory or ambiguous phylogenetic results from most sequenced loci analyzed separately (table 14), the monophyly of Didelphis is strongly supported by parsimony and Bayesian analyses of morphology (fig. 27), a concatenated five-gene dataset (fig. 33), and combined (nonmolecular + molecular) supermatrices (figs. 35, 36). Revisionary studies of the genus Didelphis in its modern sense were initiated by Allen (1901, 1902) and continued by Krumbiegel (1941), Gardner (1973), Cerqueira (1985), and Lemos and Cerqueira (2002). Useful summaries of morphological characters that distinguish Didelphis species in local faunas are provided by Mondolfi and Pérez-Hernández (1984), Catzeflis et al. (1997), Cerqueira and Lemos (2000), Flores and Abdala (2001), and Ventura et al. (2002). Analyses of mitochondrial DNA sequence variation within and among South American species were reported by Patton et al. (2000) and Patton and Costa (2003).