Cryptonanus Voss et al., 2005

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 : 126-128

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Cryptonanus Voss et al., 2005


Cryptonanus Voss et al., 2005   Figure 49

CONTENTS: agricolai Moojen, 1943   ; chacoensis Tate, 1931   ; guahybae Tate, 1931   ; ignitus Díaz et al., 2002   ; and unduaviensis Tate, 1931   .

MORPHOLOGICAL DESCRIPTION: Combined length of adult head and body ca. 80– 120 mm; adult weight ca. 15–40 g. Ventral margin of rhinarium with two shallow grooves on each side of median sulcus; dark circumocular mask present; pale supraocular spot absent; dark midrostral stripe absent; gular gland present in adult males. Dorsal body pelage unpatterned, usually grayish or reddish brown; dorsal fur gray based; dorsal guard hairs very short and inconspicuous; ventral fur gray based or self-colored (varying among species). Manus paraxonic (dIII 5 dIV); manual claws shorter than fleshy apical pads of digits; dermatoglyph-bearing manual plantar pads present; central palmar surface of manus sparsely tubercular (neither smooth nor densely covered with convex tubercles); lateral carpal tubercles present in adult males. Pedal digits unwebbed   ; dIV longer than other pedal digits; plantar epithelium of heel naked. Pouch absent   ; mammae 4–1–4 5 9 (all abdominal-inguinal) to 7–1–7 5 15 (with pectoral teats); cloaca present. Tail longer than combined length of head and body, slender and muscular (not incrassate); body pelage not extending more than a few mm onto tail base; unfurred caudal integument more or less bicolored (dark above, paler below) in most specimens; caudal scales in distinctly annular series, each scale with three subequal bristlelike hairs emerging from distal margin; ventral caudal surface modified for prehension distally, with apical pad bearing dermatoglyphs.

Rostral process of premaxillae absent. Nasals long, extending anteriorly beyond I1 (concealing nasal orifice from dorsal view), and conspicuously widened posteriorly near maxillary-frontal suture. Maxillary turbinals large and elaborately branched. Two lacrimal foramina laterally exposed on each side on or just anterior to orbital margin. Supraorbital margins rounded, without beads or processes (a few old individuals have incipient postorbital processes); distinct interorbital and postorbital constrictions usually present in juveniles and young adults. Left and right frontals and parietals separated by persistent median sutures. Parietal and alisphenoid in contact on lateral braincase (no squamosalfrontal contact). Sagittal crest absent. Petrosal laterally exposed through fenestra in parietal-squamosal suture. Parietal-mastoid contact present (interparietal does not contact squamosal).

Maxillopalatine fenestrae large; palatine fenestrae present; maxillary fenestrae absent; posterolateral palatal foramina small, not extending lingual to M4 protocones; posteri- or palate conforms to Didelphis   morphotype (with prominent lateral corners, the internal choanae abruptly constricted behind). Maxillary and alisphenoid not in contact on orbital floor (separated by palatine). Transverse canal foramen present. Alisphenoid tympanic process smoothly globular, without anteromedial process or posteromedial lamina enclosing extracranial course of mandib- ular nerve (secondary foramen ovale absent), and not contacting rostral tympanic process of petrosal. Anterior limb of ectotympanic directly suspended from basicranium. Stapes triangular, perforated by 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 formed by supraoccipital and exoccipitals, incisura occipitalis present.

Two mental foramina 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, slightly increasing in length (mesiodistal dimension) from I2 to I5. Upper canine (C1) alveolus in premaxillary-maxillary suture; C1 usually with one or two small accessory cusps (the posterior accessory cusp is more consistently distinct than the anterior cusp). 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. Upper molars strongly carnassialized (postmetacristae conspicuously longer than postprotocristae); relative widths M1, M2, M3. M4 or M1, M2, M3, M4; centrocrista strongly inflected labially on M1–M3; ectoflexus shallow or absent on M1, deeper on M2, and consistently deep on M3; anterolabial cingulum continuous with preprotocrista (complete anterior cingulum present) on M 3 in some species (e.g., C. unduaviensis   ) but anterolabial cingulum and preprotocrista discontinuous (anterior cingulum incomplete) on M 3 in others (e.g., C. chacoensis   ); postprotocrista without carnassial notch. Last upper tooth to erupt is P3.

Lower incisors (i1–i4) with distinct lingual cusps. Lower canine (c1) procumbent, with flattened bladelike apex, usually with small posterior accessory cusp (but often absent on even moderately worn teeth). Second lower premolar (p2) taller than p3; lower milk premolar (dp3) with complete trigonid (tricuspid in in C. chacoensis   ) or with incomplete trigonid (bicuspid in C. unduaviensis   ). Hypoconid labially salient (level with labial apex of protoconid) on m3; hypoconulid twinned with entoconid on m1–m3; entoconid much taller than hypoconulid on m1–m3.

DISTRIBUTION: Cryptonanus   is known from mostly unforested tropical and subtropical biomes south of the Amazon River and east of the Andes, including the Caatinga, Cerrado, Chaco, and northern Pampas; collection localities mapped by Voss et al. (2005) and D’Elía and Martínez (2006) are from Paraguay, Uruguay, eastern Bolivia, northern Argentina, and eastern Brazil.

REMARKS: Our species-level taxonomy of Cryptonanus   follows Voss et al. (2005) who, however, cautioned that this arrangement is provisional and unsupported by rigorous tests of species limits. In particular, the genetic distinctness of C. agricolai   , C. chacoensis   , C. ignitus   , and C. unduaviensis   is not overwhelmingly indicated by available morphological data and merits careful evaluation. Molecular sequence comparisons would be an especially welcome supplement to the scant phenotypic evidence at hand.