Glironia Thomas, 1912

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 : 89-91

Glironia Thomas, 1912 Figure 37

CONTENTS: venusta Thomas, 1912 (including aequatorialis Anthony, 1926; and criniger Anthony, 1926).

MORPHOLOGICAL DESCRIPTION: Combined length of adult head and body probably ca. 170–210 mm; adult weight probably ca. 100– 200 g (measurements from the only two adult specimens known to have been measured by the American method and accompanied by weight data are in table 4). 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 unknown (no suitably preserved adult male specimens have been examined for this feature). Dorsal body pelage unpatterned, brownish ; dorsal underfur gray; dorsal guard hairs short and inconspicuous; ventral fur grayish or gray-based whitish, with or without self-whitish pectoral markings. Manus paraxonic (dIII 5 dIV); manual claws strongly recurved, laterally compressed, and much longer than fleshy apical pads of digits; dermatoglyph-bearing manual plantar pads present; central palmar epithelium smooth; carpal tubercles absent. Pes unwebbed ; dIV longer than other pedal digits; plantar surface of heel naked. Pouch absent ; mammae 2–0–2 5 4, all abdominal/inguinal; cloaca present. Tail about as long as combined length of head and body or a little longer, slender and muscular (not incrassate), and densely furred from base to tip except along ventral midline; naked ventral caudal surface modified for prehension with raised tubercles near base and apical pad bearing dermatoglyphs.

Premaxillary rostral process absent. Nasals long, extending anteriorly beyond I1 (concealing nasal orifice from dorsal view), and conspicuously widened posteriorly near maxillary-frontal suture. Maxillary turbinals elaborately branched. Lacrimal foramina concealed within anterior orbital margin or exposed laterally, usually two on each side. Orbits very large; supraorbital crests well developed; flattened triangular postorbital processes present, formed by both frontal and parietal bones. Left and right frontals and parietals separated by persistent median sutures. Parietal contacts alisphenoid on lateral braincase (no frontal-squamosal contact). Sagittal crest absent. Petrosal not laterally exposed through fenestra in parietal-squamosal suture (fenestra absent). Parietal-mastoid contact present (interparietal does not contact squamosal).

Maxillopalatine fenestrae usually present, but small; palatine fenestrae absent; maxillary fenestrae absent; posterolateral palatal foramina small, not extending anteriorly between M4 protocones; posterior palatal morphology Caluromys -like (without prominent lateral corners, the choanae not constrict- ed behind). Maxillary and alisphenoid not in contact on floor of orbit (separated by palatine). Transverse canal foramen present. Alisphenoid tympanic process smoothly globular, without anteromedial process or posteromedial lamina enclosing extracranial course of mandibular nerve (secondary foramen ovale absent), and not in contact with rostral tympanic process of petrosal. Anterior limb of ectotympanic suspended directly from basicranium. Stapes triangular with large obturator foramen. Fenestra cochleae exposed, not concealed by rostral and caudal tympanic processes of petrosal. Paroccipital process small, adnate to petrosal. Dorsal margin of foramen magnum bordered by exoccipitals and supraoccipital, incisura occipitalis present.

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

Unworn crowns of I2–I5 asymmetrical (‘‘incisiform’’), with longer anterior than posterior cutting edges; I5 separated from I4 by small diastema in some specimens (e.g., INPA 2570) but not others (e.g., FMNH 41440). Upper canine (C1) alveolus in premaxillary-maxillary suture; C1 simple, without accessory cusps. First upper premolar (P1) present, smaller than more posterior premolars but well formed and not vestigial; second and third upper premolars (P2 and P3) subequal in height; P3 with both anterior and posterior cutting edges. Molars weakly carnassialized (postmetacristae longer than postprotocristae); relative widths M1, M2, M3. M4; centrocrista weakly inflected labially on M1–M3; ectoflexus absent or indistinct on M1 and M2, distinct but usually shallow on M3; 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 lower premolar (p2) taller than p3; morphology of lower milk premolar (dp3) unknown (no juvenile specimens examined). Hypoconid labially salient on m3; hypoconulids twinned with entoconids on m1–m3; entoconids much taller than hypoconulids on m1–m3.

DISTRIBUTION: Glironia is currently known from fewer than two dozen specimens collected at widely scattered localities between 300 and 1000 m above sea level in Brazil (Amazonas, Mato Grosso, Pará, Rodônia), eastern Ecuador, eastern Peru, and eastern Bolivia ( Díaz and Willig, 2004; Santos-Filho et al., 2007; Barkley, 2008). Although the genus probably also occurs in southeastern Colombia, no specimens are known to have been collected there ( Díaz and Willig, 2004). Most records accompanied by definite habitat information are from primary or secondary Amazonian rainforest, but a single specimen was recently reported from the upper Paraguay Basin ( Santos-Filho et al., 2007), and several Bolivian records are from dry forest ( Tarifa and Anderson, 1997; Emmons, 1998).

REMARKS: Only the type species of Glironia is currently recognized as valid, but it seems probable that additional taxa are represented among the material now preserved in museum collections.