phylogenetic relationships and classification of didelphid marsupials ...

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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
2009 VOSS AND JANSA: DIDELPHID MARSUPIALS 95 many subjective synonyms listed above for either C. philander or C. lanatus. It is an open question as to whether the subgenera Caluromys and Mallodelphys will prove to be reciprocally monophyletic or not in future phylogenetic analyses based on denser taxon sampling. Caluromysiops Sanborn, 1951 Figure 39 CONTENTS: irrupta Sanborn, 1951. MORPHOLOGICAL DESCRIPTION: Combined length of adult head and body probably ca. 250–300 mm (Izor and Pine, 1987); adult weight probably ca. 300–500 g. Rhinarium with two ventrolateral grooves on each side of median sulcus; fur of head uniformly pale, without any marking (dark circumocular mask, supraocular spots, and midrostral stripes absent); throat gland absent. Dorsal pelage pale overall but prominently marked by paired blackish stripes extending from forelimbs to shoulders and thence posteriorly as narrowing parallel bands to rump; dorsal underfur dark (apparently grayish but discolored with age in all examined specimens); dorsal guard hairs short; ventral fur variously colored (gray-based buffy in some specimens, self-buffy in others). Manual digit IV longer than other manual digits; manual claws longer than fleshy apical pads of digits; dermatoglyph-bearing manual plantar pads present; central palmar epithelium smooth; carpal tubercles absent. Pedal digits unwebbed; dIV longer than other pedal digits; plantar surface of heel usually naked. Pouch said to be present (Izor and Pine, 1987) but morphological details unknown; mammary formula unknown; cloaca present. Tail longer than combined length of head and body, slender and muscular (not incrassate); densely covered with body fur from base almost to tip except along ventral midline and posterolaterally; posterolateral caudal scales in spiral series, each scale with three subequal bristlelike hairs emerging from distal margin; naked ventral surface modified for prehension with raised tubercles near base, and apical pad bearing dermatoglyphs. Premaxillary rostral process absent. Nasals long, extending anteriorly above I1 (conceal- ing nasal orifice from dorsal view), and conspicuously widened posteriorly near maxillary-frontal suture. Maxillary turbinals elaborately branched. One or two lacrimal foramina exposed on each side on or near anterior orbital margin. Large flattened, triangular postorbital processes of frontals present, continuous with supraorbital crests. Left and right frontals and parietals coossified in most adult specimens (median sutures incomplete or obliterated). Parietal and alisphenoid in contact on lateral braincase (no frontal-squamosal contact). Sagittal crest present, prominently developed on parietals and extending onto frontals in most adult specimens. Petrosal not laterally exposed through fenestra in parietal-squamosal suture (fenestra absent). Parietal-mastoid contact present (interparietal does not contact squamosal). Maxillopalatine, palatine, and maxillary fenestrae absent (palate completely ossified); posterolateral palatal foramina small, not extending anteriorly between M4 protocones; posterior palatal morphology conforms to Caluromys morphotype (without strongly developed lateral corners, the choanae unconstricted behind). Maxillary and alisphenoid widely separated by palatine on floor of orbit. Transverse canal foramen absent. Alisphenoid tympanic process smoothly globular, apparently always with posteromedial lamina enclosing extracranial course of mandibular nerve (secondary foramen ovale present), and extending posteriorly to contact or closely approximate rostral tympanic process of petrosal. Anterior limb of ectotympanic indirectly suspended from basicranium (by malleus). Stapes usually columellar and imperforate (rarely microperforate). Fenestra cochleae usually concealed in sinus formed by rostral and caudal tympanic processes of petrosal (but not in USNM 397626, possibly due to pathology or postmortem damage). Paroccipital process small, 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 obtuse, weakly inflected. Unworn crowns of I2–I5 asymmetrical (‘‘incisiform’’), with longer anterior than
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PHYLOGENETIC RELATIONSHIPS AND CLAS
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CONTENTS Abstract .................
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ABSTRACT This report summarizes a d
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