Marmosops Matschie, 1916

Díaz-Nieto, Juan F. & Voss, Robert S., 2016, A Revision Of The Didelphid Marsupial Genus Marmosops, Part 1. Species Of The Subgenus Sciophanes, Bulletin of the American Museum of Natural History 2016 (402), pp. 1-72 : 14-15

Genus Marmosops Matschie, 1916

TYPE SPECIES: Marmosops incanus ( Lund, 1840) by original designation.

CONTENTS: At least 19 species (as recognized by Voss and Jansa, 2009; Voss et al., 2013; Díaz-Nieto et al., 2016a; and this report) in two subgenera.

DESCRIPTION: 2 Combined length of adult head and body ca. 90–195 mm; adult weight ca. 20–140 g. Rhinarium with two ventrolateral grooves on each side of median sulcus; dark circumocular mask present; pale supraocular spot absent; dark midrostral stripe absent; throat gland consistently present in adult males of some species (e.g., M. incanus , M. noctivagus ) but apparently absent in others (e.g., M. caucae , M. parvidens ). Dorsal pelage unpatterned, usually some shade of dull grayish brown, but distinctly redder or grayer in some species; dorsal hair bases always dark gray; dorsal guard hairs short and inconspicuous; ventral fur self-colored (whitish, buffy, or brown) or entirely or partially gray based. Manus mesaxonic (dIII> dIV); manual claws small, shorter than fleshy apical pads of digits; dermatoglyph-bearing manual plantar pads present; central palmar epithelium smooth or sparsely tuberculate; lateral carpal tubercles externally conspicuous on wrists of large adult males of most species; medial carpal tubercles absent in both sexes. Pedal digits unwebbed; dIV longer than other pedal digits; plantar surface of heel macroscopically naked (a microscopic pelage of very short hairs, not coarse fur, is usually 2 After Voss and Jansa (2009: 134–137), but including minor corrections and supplementary observations of character variation discovered in the course of this study.

present). Pouch absent; mammae varying among examined species from 3–1–3 = 7 to 7–1–7 = 15 (anteriormost pairs “pectoral” when mammae ≥ 11; e.g., in M. ocellatus ); cloaca present. Tail longer than combined length of head and body, slender and muscular (not incrassate), and macroscopically naked (without a conspicuously furred base); naked caudal integument uniformly dark (usually grayish), bicolored (dark above, pale below), or particolored (dark proximally, paler distally); caudal scales in spiral series, each scale with three bristlelike hairs emerging from caudal margin; median hair of each caudal-scale triplet usually much thicker and darker than lateral hairs; ventral caudal surface modified for prehension distally (with naked median groove and apical pad bearing dermatoglyphs).

Premaxillary rostral process long and well developed in some species (e.g., M. parvidens , M. pinheiroi ) but short in others (e.g., M. noctivagus ) and apparently absent in some ( M. incanus ). Nasals long, extending anteriorly beyond I1 (concealing nasal orifice in dorsal view), and conspicuously widened posteriorly near maxillary-frontal suture except in M. carri , M. fuscatus , and M. incanus (which have narrow, more or less parallelsided nasals). Maxillary turbinals (viewed through nasal orifice) elaborately branched. Lacrimal foramina usually two on each side, concealed from lateral view inside orbit (e.g., in M. parvidens ) or exposed on orbital margin (e.g., in M. pinheiroi ). Interorbital region without abrupt constrictions; supraorbital margins rounded in some species (e.g., M. parvidens ), beaded in others (e.g., M. noctivagus ); postorbital processes usually absent. Left and right frontals and parietals separated by persistent median sutures. Parietal and alisphenoid in contact on lateral braincase (no frontal-squamosal contact). Sagittal crest absent. Petrosal consistently exposed laterally through fenestra in parietal-squamosal suture in most species (but fenestra polymorphically absent in M. incanus and M. noctivagus ). Parietal-mastoid contact present (interparietal does not contact squamosal).

Maxillopalatine fenestrae present; palatine fenestrae present in some species (e.g., M. creightoni ), but absent in others (e.g., M. pinheiroi ); maxillary fenestrae absent; posterolateral palatal foramina small, not extending anteriorly lingual to M4 protocones; posterior palate 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 well-developed 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 premaxillarymaxillary suture; C1 without accessory cusps in some species (e.g., M. creightoni ), or with only posterior accessory cusp (e.g., M. invictus ), or with both anterior and posterior accessory cusps (e.g., M. parvidens ). 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 M 3 in some species (e.g., M. noctivagus ), but anterolabial cingulum narrowly 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. Lower canine (c1) distinctively tall, recurved, and unicuspid in some species (e.g., M. noctivagus ), but smaller and premolariform in others (e.g., M. pinheiroi ). Second lower premolar (p2) subequal in height to p 3 in some species (e.g., M. incanus ) but distinctly taller than p 3 in most others; 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.

REMARKS: As discussed by Voss and Jansa (2009: 137–138), the monophyly of the genus Marmosops is strongly supported by phylogenetic analyses of nuclear exon sequences and by combined analyses of nuclear genes and morphological characters. In the latter analyses, several morphological traits optimized as generic synapomorphies, including (1) spirally arranged caudal scales, (2) the petiolate morphology of the central hair in each caudal-scale triplet, and (3) the presence of a distinct rostral process of the premaxillae. Generic monophyly is also supported by unique deletions at the DMP1 and BRCA1 loci ( Voss and Jansa, 2009: figs. 29, 31). The monophyly of Marmosops was additionally corroborated in recent phylogenetic analyses with much denser taxon sampling by Díaz-Nieto et al. (2016a, 2016b), who sequenced several genes not included in Voss and Jansa’s (2009) study. As discussed elsewhere ( Voss and Jansa, 2003: 56–57), DNA-DNA hybridization results reported by Kirsch and Palma (1995) and Kirsch et al. (1997) that recovered Gracilinanus nested inside the genus Marmosops are unambiguously attributable to misidentified voucher material. Diagnostic morphological comparisons among Marmosops and other didelphid genera with which it was formerly confused ( Gracilinanus , Marmosa , and Thylamys ) were described, illustrated, and tabulated by Voss et al. (2004).