Marmosa (Stegomarmosa) lepida (Thomas, 1888)

Voss, Robert S., Fleck, David W. & Jansa, Sharon A., 2019, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 3: Marsupials (Didelphimorphia), Bulletin of the American Museum of Natural History 2019 (432), pp. 1-89 : 32-33

Marmosa (Stegomarmosa) lepida

(Thomas, 1888)

Figures 9B , 10B

VOUCHER MATERIAL (TOTAL = 1): Nuevo San Juan (AMNH 273186).

OTHER INTERFLUVIAL RECORDS: None.

IDENTIFICATION: Our unique voucher, an adult male preserved in fluid with the skull extracted and cleaned, exhibits all the diagnostic traits of the nominotypical form ( Marmosa lepida lepida ), including small size, reddish dorsal fur, a midventral zone of self-whitish fur flanked by lateral zones of gray-based fur, a long tail with dense fringes of silvery hairs flanking the distal prehensile surface, a very long rostral process of the premaxillae, large postorbital processes, and small posterior accessory cusps on C1 and c1. Additionally,

our specimen lacks any trace of a gular gland, and palatine fenestrae are absent. Morphometric comparisons with other specimens from western Amazonia, including the holotype, suggest striking uniformity in most craniodental dimensions, especially of the molar dentition (table 9). A cytochrome b sequence obtained from AMNH 273186 was analyzed by Gutiérrez et al. (2010), who reported that it formed a strongly supported clade with sequences from other specimens that also exhibit the distinctive morphological traits of M. lepida .

The only local taxa with which Marmosa lepida could possibly be confused in the field are Hyladelphys kalinowskii and Gracilinanus emiliae , both of which are also small, reddish, black-masked, and long-tailed. Comparisons with Hyladelphys kalinowskii have already been described, but it remains to compare M. lepida with G. emiliae . The chief external character distinguishing these taxa (table 4) is the ventral coloration (self-whitish and gray-based in M. lepida versus entirely self-white in G. emiliae ). Crania of these species (figs. 9, 10) are most easily distinguished by the occurrence of postorbital processes (present in M. lepida , absent in G. emiliae ), palatine fenestrae (absent in M. lepida , present in G. emiliae ), and secondary foramina ovales (usually absent in M. lepida , consistently present in G. emiliae ); additionally, the upper molar series is much longer in M. lepida (LM = 5.6–6.1 mm) than in G. emiliae (LM = 4.8–5.1 mm).

Two subspecies of Marmosa lepida were recognized by Tate (1933), of which our material is unambiguously referable to the nominotypical form. Marmosa l. lepida occurs on both sides of the Amazon, from the base of the Andes to the Atlantic coast, with remarkably little evidence of geographic variation in either morphology or cytochrome b sequences ( Tate, 1933; Gutiérrez et al., 2010; Guimarães et al., 2018). By contrast, M. l. grandis Tate, 1931, is known only from Buenavista in Santa Cruz province, Bolivia. We examined the young adult female holotype of grandis (BMNH 26.12.4.94), which differs from other specimens of M. lepida in ventral pelage color (entirely gray-based buffy) and in lacking posterior accessory cusps on C1 and c1. Given the morphological uniformity exhibited by Amazonian specimens of M. lepida , we are not persuaded that grandis is really conspecific. Although Tate (1933: 205) listed two specimens that he identified as M. l. lepida from Buenavista (paradoxically implying sympatry of two subspecies), the specimens in question are offspring of the holotype of grandis (as documented by notes on the skin tags). We have not examined any Bolivian specimen definitely referable to typical M. lepida as diagnosed by the suite of traits listed in the first paragraph of this account.

ETHNOBIOLOGY: The Matses do not distinguish this species from other pouchless, longtailed, black-masked species of small opossums (all known as chekampi; see the account for Marmosa , above) and therefore have no particular beliefs about it.

MATSES NATURAL HISTORY: The Matses have no definite knowledge of this species.

REMARKS: Our single specimen was shot at night by a Matses hunter as it perched in the subcanopy of tall primary forest.

OTHER SPECIMENS EXAMINED (TOTAL = 13): Brazil — Amazonas, Igarapé Grande on Rio Juruá (FMNH 140824) . Colombia — Amazonas , 20 km downstream from La Chorrera on Río Igaraparaná (MNHN 1982-653) . French Guiana —Les Nouragues (MNHN 1998-306). Guyana — Potaro-Siparuni, 42 km WNW Siparuni (ROM 107034) . Ecuador — Pastaza, Río Tigre (AMNH 182937) ; Sucumbíos, L ago Ag r io (KU 1 3 5 1 1 8) . Peru — Amazonas, Huampami on Río Cenepa (MVZ 154750, 154752, 155245) ; Loreto, Río Pisqui (AMNH 98656), Santa Cruz on Río Huallaga below Yurimaguas (BMNH 69.3.31.4 [holotype]) ; Ucayali, Lagarto (AMNH 78001) . Venezuela — Amazonas, El Platanal (EBD, uncataloged) .

Figures

FIG. 9. Dorsal and ventral cranial views of three small opossums. A, Hyladelphys kalinowskii (AMNH 267338, an adult male from French Guiana); B, Marmosa lepida (AMNH 273186, an adult male from the Yavarí- Ucayali interfluve); C, Gracilinanus emiliae (MUSM 15292, an adult female from the Yavarí-Ucayali interfluve). Abbreviations: amp, anteromedial process of the alisphenoid bulla (enclosing a secondary foramen ovale); pal, palatine fenestra; pop, postorbital process (of frontal); rp, rostral process (of premaxilla).

FIG. 10. Lateral cranial views of three small opossums (same specimens as in fig. 9). A, Hyladelphys kalinowskii; B, Marmosa lepida; C, Gracilinanus emiliae. Abbreviations: P2, second upper premolar; P3, third upper premolar; pac, posterior accessory cusp (of upper canine); rp, rostral process (of premaxilla).