128 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 322 ular nerve (secondary foramen ovale absent), <strong>and</strong> not contacting rostral tympanic process <strong>of</strong> petrosal. Anterior limb <strong>of</strong> ectotympanic directly suspended from basicranium. Stapes triangular, perforated by large obturator foramen. Fenestra cochleae exposed, not concealed by rostral <strong>and</strong> caudal tympanic processes <strong>of</strong> petrosal. Paroccipital process small, adnate to petrosal. Dorsal margin <strong>of</strong> foramen magnum formed by supraoccipital <strong>and</strong> exoccipitals, incisura occipitalis present. Two mental foramina present on lateral surface <strong>of</strong> each hemim<strong>and</strong>ible; angular process acute <strong>and</strong> strongly inflected. Unworn crowns <strong>of</strong> I2–I5 symmetrically rhomboidal (‘‘premolariform’’), with subequal anterior <strong>and</strong> 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 <strong>and</strong> not vestigial; third upper premolar (P3) taller than P2; P3 with posterior cutting edge only; upper milk premolar (dP3) large <strong>and</strong> 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; ect<strong>of</strong>lexus shallow or absent on M1, deeper on M2, <strong>and</strong> consistently deep on M3; anterolabial cingulum continuous with preprotocrista (complete anterior cingulum present) on M3 in some species (e.g., C. unduaviensis) but anterolabial cingulum <strong>and</strong> preprotocrista discontinuous (anterior cingulum incomplete) on M3 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 <strong>of</strong>ten 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 <strong>of</strong> 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 <strong>and</strong> subtropical biomes south <strong>of</strong> the Amazon River <strong>and</strong> east <strong>of</strong> the Andes, including the Caatinga, Cerrado, Chaco, <strong>and</strong> northern Pampas; collection localities mapped by Voss et al. (2005) <strong>and</strong> D’Elía <strong>and</strong> Martínez (2006) are from Paraguay, Uruguay, eastern Bolivia, northern Argentina, <strong>and</strong> eastern Brazil. REMARKS: Our species-level taxonomy <strong>of</strong> Cryptonanus follows Voss et al. (2005) who, however, cautioned that this arrangement is provisional <strong>and</strong> unsupported by rigorous tests <strong>of</strong> species limits. In particular, the genetic distinctness <strong>of</strong> C. agricolai, C. chacoensis, C. ignitus, <strong>and</strong> C. unduaviensis is not overwhelmingly indicated by available morphological data <strong>and</strong> merits careful evaluation. Molecular sequence comparisons would be an especially welcome supplement to the scant phenotypic evidence at h<strong>and</strong>. Gracilinanus Gardner <strong>and</strong> Creighton, 1989 Figure 50 CONTENTS: aceramarcae Tate, 1931; agilis Burmeister, 1854 (including beatrix Thomas, 1910; buenavistae Tate, 1931; <strong>and</strong> peruana Tate, 1931); dryas Thomas, 1898; emiliae Thomas, 1909 (including longicaudus Hershkovitz, 1992); marica Thomas, 1898 (including perijae Hershkovitz, 1992); <strong>and</strong> microtarsus Wagner (1842). MORPHOLOGICAL DESCRIPTION: Combined length <strong>of</strong> adult head <strong>and</strong> body ca. 75– 130 mm; adult weight ca. 10–50 g. Rhinarium with two ventrolateral grooves on each side <strong>of</strong> median sulcus; dark circumocular mask present; pale supraocular spot absent; dark midrostral stripe absent; throat gl<strong>and</strong> present in adult males. Dorsal pelage unpatterned reddish or grayish brown with dark-gray hair bases; dorsal guard hairs short <strong>and</strong> inconspicuous; ventral fur mostly gray-based buff or orange (e.g., in G. microtarsus), but self-white in some species (e.g., G. emiliae). Manus paraxonic (dIII 5 dIV); manual claws small, not extending beyond fleshy apical pads <strong>of</strong> digits; dermatoglyph-bearing manual plantar pads
2009 VOSS AND JANSA: DIDELPHID MARSUPIALS 129 Fig. 50. Gracilinanus agilis (based on MVZ 197437, an adult male from Mato do Vasco, Minas Gerais, Brazil).