Philander Brisson, 1762

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 : 121-124

Philander Brisson, 1762 Figure 48

CONTENTS: andersoni Osgood, 1913 (including nigratus Thomas, 1923); deltae Lew et al., 2006; frenatus Olfers, 1818 (including azaricus Thomas, 1923; quica Temminck, 1824 ; and superciliaris Olfers, 1818); mcilhennyi Gardner and Patton, 1972 ; mondolfii Lew et al., 2006; olrogi Flores et al., 2008; and opossum Linnaeus, 1758 (including canus Osgood, 1913; crucialis Thomas, 1923; fuscogriseus J.A. Allen, 1900; grisescens J.A. Allen, 1901; melantho Thomas, 1923; melanurus Thomas, 1899; pallidus J.A. Allen, 1901; and virginianus Tiedemann, 1808).

MORPHOLOGICAL DESCRIPTION: Combined length of adult head and body ca. 250– 350 mm; adult weight ca. 280–700 g. Rhinar- ium with one ventrolateral groove on each side of median sulcus; dark circumocular mask present, usually continuous with dark coronal fur (the coronal fur is not dark in some examined specimens of P. frenatus ); pale supraocular spot present; dark midrostral stripe absent; throat gland absent. Dorsal pelage unpatterned grayish or blackish, or with grayish flanks and black middorsal stripe; dorsal underfur gray; dorsal guard hairs usually short (longer middorsally than along flanks in P. mcilhennyi ); ventral fur variously pigmented, usually gray-based buffy or cream, or entirely grayish (variable within and among examined taxa). Manus mesaxonic (dIII. dIV); manual claws about as long as fleshy apical pads of digits; dermatoglyph-bearing manual plantar pads present; central palmar epithelium smooth or sparsely tuberculate; carpal tubercles absent. Pedal digits unwebbed; dIV longer than other pedal digits; plantar surface of heel naked. Pouch present, opening anteriorly; mammae usually 2–1–2 5 5 or 3–1–3 5 7; cloaca present. Tail longer than combined length of head and body, slender and muscular (not incrassate); furred dorsally and ventrally to about the same extent for basal one-fifth; naked caudal integument blackish proximally and abruptly whitish distally; caudal scales in spiral series, each scale with 4–6 bristlelike hairs emerging from distal margin; ventral caudal surface modified for prehension distally, with apical pad bearing dermatoglyphs.

Premaxillary rostral process absent. Nasals short, not extending anteriorly above I1 (exposing nasal orifice in dorsal view), and widened posteriorly near maxillary-frontal suture. Maxillary turbinals elaborately branched. Lacrimal foramina usually two on each side, exposed laterally on orbital margin or on face just anterior to orbit. Interorbital region smoothly rounded, without supraorbital beads or crests; short, blunt, hornlike postorbital processes usually present in large adult specimens. 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 frontal-squamosal contact). Sagittal crest present, well developed on parietals and extending anteriorly 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 small, not extending anteriorly between M4 protocones; posterior palatal morphology conforming to Didelphis morphotype (with prominent lateral corners, the choanae constricted behind). Maxillary and alisphenoid usually separated by palatine on floor of orbit (maxillary-alisphenoid contact occurs unilaterally or bilaterally in a few specimens). Transverse canal foramen usually present. Alisphenoid tympanic process small and uninflated, usually with broad lamina enclosing extracranial course of mandibular nerve (secondary foramen ovale present), and not contacting rostral tympanic process of petrosal. Anterior limb of ectotympanic indirectly suspended from basicranium (by malleus). Stapes usually triangular with large obturator foramen. Fenestra cochleae exposed (not concealed by rostral and caudal tympanic processes of petrosal). Paroccipital process large, erect, directed posteroventrally. Dorsal margin of foramen magnum bordered by exoccipitals only, incisura occipitalis absent.

Two mental foramina present on lateral surface of each hemimandible; angular process acute and strongly inflected.

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 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; centrocrista only weakly inflected labially on M1–M3; ectoflexus usually distinct only 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. Lower canine (c1) erect, acutely pointed, and simple (without a posterior accessory cusp). Second lower premolar (p2) much taller than p3; lower milk premolar (dp3) large and molariform 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: Species of Philander occur in lowland and lower montane moist forests (to 1600 m; Reid, 1997) from the Mexican state of Tamaulipas southward throughout most of Central America ( Hall, 1981) and tropical South America ( Patton and da Silva, 2008) to northern Argentina (Chaco, Formosa, and Misiones; Flores et al., 2007). Collecting localities mapped by Anderson (1997), Linares (1998), and Brown (2004) suggest that Philander is largely absent from intervening arid, semiarid, or treeless landscapes (e.g., the Chaco, Cerrado, Caatinga, and Llanos), with a few exceptions that may have been taken in gallery forests.

REMARKS: Although inconsistently supported by our separate nuclear-gene analyses (table 14) and by Patton et al.’s (1996) analyses of sequence data from the mitochondrial cytochrome b locus, the monophyly of Philander is moderately well supported by nonmolecular characters (fig. 27) and it is strongly supported by our analyses of concatenated genes and combined datasets (figs. 33, 35, 36). The current species-level classification given above largely follows Patton and da Silva (1997), who analyzed mtDNA haplotype diversity among 42 Central and South American specimens that they interpreted as representing six valid taxa ( andersoni , canus, frenatus , fuscogriseus, mcilhennyi , opossum ); three unsequenced taxa (azarica, melanurus, pallidus) were also recognized as valid on the basis of morphological traits. Whereas andersoni , frenatus , and mcilhennyi were recovered as monophyletic haplotype groups that Patton and da Silva recognized as monotypic species, their concept of opossum included several subspecies (azarica, canus, fuscogriseus, melanurus, pallida) and was not recovered as a clade. Based on their phylogenetic analysis (op. cit.: fig. 2), it would be logical to recognize fuscogriseus and canus as valid species, but the authors reasonably cautioned against facile taxonomic decisions based on the results of analyzing a single maternally inherited gene. Indeed, the genus clearly requires a more comprehensive revisionary treatment, with particular attention devoted to obtaining analyzable character data from hitherto unrepresented taxa (notably azarica, crucialis, grisescens, melanurus, and pallidus). Our placement of azarica in the synonymy of P. frenatus uncritically follows Gardner (2005), who also allocated nominal taxa not treated by Patton and da Silva (1997) to the synonymy of P. opossum . Although an alternative species-level classification of Philander proposed by Hershkovitz (1997) was not based on any explicit analysis of specimen data, it raised several issues not adequately treated by other authors and drew attention to the possible existence of undescribed taxa. New species described by Lew et al. (2006) and Flores et al. (2008) contribute additional taxonomic complexities and underscore the need for critical revisionary work on this difficult genus.

The tiresome nomenclatural controversy regarding the use of Philander Tiedemann, 1808 , versus Metachirops Matschie, 1916 , as the correct generic name for the gray foureyed opossums ( Pine, 1973; Hershkovitz, 1976; Gardner, 1981) was made moot by a recent ruling of the International Commission on Zoological Nomenclature (ICZN, 1998) that definitively established the availability of Philander from Brisson (1762).