An Introduction to Marmosops (Marsupialia: Didelphidae), with the Description of a New Species from Bolivia and Notes on the Taxonomy and Distribution of Other Bolivian Forms Author VOSS, ROBERT S. Author TARIFA, TERESA Author YENSEN, ERIC text American Museum Novitates 2004 2004-12-30 3466 1 40 http://www.bioone.org/doi/abs/10.1206/0003-0082%282004%29466%3C0001%3AAITMMD%3E2.0.CO%3B2 journal article 3781 10.1206/0003-0082(2004)466<0001:AITMMD>2.0.CO;2 b3293c54-11ba-43d8-8c3c-243a8c05d6cd 0003-0082 4735089 Marmosops ocellatus Judging from the large numbers of specimens in museum collections, Marmosops ocellatus is the commonest (or most frequently trapped) small marsupial throughout most of Santa Cruz department , from the base of the Andes to the Brazilian frontier (fig. 12). Currently considered to be a junior synonym of dorothea (= M. noctivagus in our usage; see above), M. ocellatus is an unambiguously diagnosable taxon that more closely resembles M. impavidus in morphology and mtDNA sequences ( tables 4 , 6 ). TABLE 10 Measurements (mm) and Weights (g) of Highland Specimens of Marmosops noctivagus , Including the Type Material of Nominal Taxa Originally Described as keaysi, dorothea , and yungasensis Externally, Marmosops ocellatus is distinctively paler than other Bolivian species, with sandy grayish­brown dorsal fur and self­cream underparts that lack distinct lateral zones of gray­based hairs. The metapodials are covered dorsally with pale (whitish) hairs that do not contrast abruptly in color with the digits. The tail is distinctly bicolored (dark above, pale below) and particolored (paler distally than proximally), such that the distal one­third or more of the organ is completely pale in most specimens. Most examined males have no trace of a gular gland, the only exception being the holotype (an unusually large specimen; table 11 ), in which the gland appears to be present. The lateral carpal tubercles of adult males are bulbous or knoblike, and the scrotum is pale (with whitish fur and unpigmented skin). Three parous adult female specimens prepared in the field by L.H. Emmons (LHE 1468, 1596, 1808) each had 6–1–6 = 13 mammae, of which the anteriormost two pairs appear to be pectoral in digital images that we examined. The supraorbital margins of the skull are rounded, lacking distinct beads even in the largest specimens, and a shallow postorbital constriction is dorsally visible. Palatine fenestrae are consistently present, the upper canine lacks accessory cusps, and the auditory bullae are moderately large. Marmosops ocellatus differs from M. impavidus by its paler and grayer dorsal coloration, absence of distinct lateral zones of gray­based ventral hairs, possession of pectoral mammae, and more distinctly bi­ and particolored tail. In addition, the palate is more extensively fenestrated and the auditory bullae are much larger in M. ocellatus than in M. impavidus . Although the difference between exemplar sequences of these taxa (about 5.7%; table 6 ) is not as large as the differences observed among other species recognized by us, the phenotypic distinctiveness of M. ocellatus and its apparently discrete geographic distribution suggest that it represents a unique evolutionary lineage that should be known by its own name. TABLE 11 Measurements (mm) and Weights (g) of Selected Specimens of Marmosops ocellatus a Most of the material that we refer to Marmosops ocellatus was identified by Anderson (1997) as M. dorothea , but two specimens (MSB 67020, 87094) were identified as Gracilinanus agilis buenavistae , and another (AMNH 263549) was identified as Thylamys macrurus . BOLIVIAN SPECIMENS EXAMINED: Santa Cruz , 6 km by road W Ascención ( AMNH 261265 ) , Aserradero Pontons ( CBF 6163 ) , Ayacucho ( USNM 390571 , 390572 ) , Buenavista ( BMNH 26.1 .5.25 [ holotype ], 28.2.9.87, 28.2.9.90), 4.5 km N and 1.5 km E Cerro Amboró ( MSB 55844) , El Refugio ( LHE 1569 , 1573 , 1577 , 1596 ) , 3.5 km W Estación El Pailon ( AMNH 260026–260028 ; MSB 55070) , Hacienda el Pelicano ( AMNH 275462 ) , 7 km E and 3 km N Ingeniero Mora ( AMNH 247652 ) , Lago Caimán ( USNM 581979 ) , 2 km SW Las Cruces ( AMNH 263549 ; MSB 63274) , Mangabalito ( MJS 005 ) , 3 km SE Montero ( MSB 87094) , Palmar ( USNM 390569 ) , San Miguel Rincón ( AMNH 260029 ) , 10 km N San Ramón ( AMNH 261266 , 261267 ) , 15 km S Santa Cruz ( MSB 58510–58514 , 59886 , 67020 ) , 27 km SE Santa Cruz (59884, 59885), Santa Rosita ( USNM 390022 ) , Tita ( MSB 55071) .