Marmosops impavidus (Tschudi, 1845)

VOSS, ROBERT S., TARIFA, TERESA & YENSEN, ERIC, 2004, 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, American Museum Novitates 3466, pp. 1-40 : 25-26

Marmosops impavidus

The application of the name impavidus is problematic because no type material is known to exist, and because Tschudi’s (1845) original description is diagnostically inadequate ( Tate, 1933: 25, 182). Current usage dates from Cabrera (1958), who used the binomen M. impavidus for the taxon that Tate (1933) recognized as M. caucae . Although the lost type material is assumed to have been collected in the eastern foothills of the Peruvian Andes, no exact location was explicitly stated in the original description. For the purposes of this report, we assume that a small series of specimens (AMNH 230017, 230018, 230020, 230022–230027) collected near San Pablo (ca. 10°27'S, 74°52'W; 275 m above sea level) in the Peruvian department of Pasco represents the typical morphology.

This a medium­size species ( table 8), larger than Marmosops bishopi but averaging smaller than typical specimens of M. noctivagus (see Patton et al. [2000] and below). The dorsal pelage is dull grayish­brown to reddish­brown, with drab (grayish) hues predominating among younger specimens and warmer (reddish) tones predominating among older adults. The ventral pelage of most Peruvian and western Brazilian specimens consists of a median strip of self­white or cream­colored fur from chin to anus, bordered by lateral zones of gray­based fur between the fore­ and hindlimbs. However, in the Peruvian material at hand (which includes specimens from Ucayali and Loreto in addition to the Pasco sample mentioned above) the relative widths of the median selfcolored and lateral gray­based zones exhibit considerable variation. The metapodials are covered with pale fur that does not contrast abruptly in color with the digits. Tails are sometimes indistinctly bicolored (paler below than above; e.g., AMNH 230017) and particolored (paler distally than proximally; e.g., AMNH 230027), but other individuals have almost unicolored tails (e.g., AMNH 76531). Adult males have knob­like lateral carpal tubercles, but none that we examined has a gular gland; the scrotal fur is white and the scrotal epithelium is unpigmented. One lactating female from Loreto ( AMNH 272709) has 3–1–3 = 7 mammae, but another from the same locality ( AMNH 273151) has 4–1–4 = 9; all of the teats in both individuals are abdominal/inguinal.

10 Unfortunately, both of the other specimens we examined from eastern Santa Cruz (LHE 1553, 1556) consist of skulls extracted from rotted specimens found in pitfall traps.

In craniodental morphology, Marmosops impavidus can be distinguished from other Bolivian congeners by the absence of supraorbital beads (usually distinct in M. noctivagus ); presence of a shallow but usually distinct postorbital constriction (usually absent in M. noctivagus ); presence of palatine fenestrae (absent in M. bishopi ); absence of accessory upper canine cusps (present in M. bishopi ); and very small, usually conical bullae.

The sole Bolivian specimen that we identify as Marmosops impavidus is MSB 57002, which was collected sympatrically with M. noctivagus at Palmira in the lowlands of Pando department (fig. 12). This specimen has redder dorsal fur and narrower nasals than do most Peruvian specimens, but its morphology is otherwise a good match with topotypical (Peruvian) material. Other Bolivian specimens previously referred to this species, however, appear to represent different taxa.

Anderson (1997: 153) reported two specimens identified as Marmosops impavidus from Incachaca in Cochabamba department, but cited only one by catalog number ( AMNH 38718); the specimen in question is a juvenile whose broken skull (originally miscataloged as 38711) exhibits incipient supraorbital beading, very short canines, and small molars (LM = 6.3 mm), traits that closely match Tate’s (1933) description of yungasensis —a taxon that we consider to be a junior synonym of M. noctivagus (see below). Two other Bolivian specimens explicitly identified by Anderson as M. impavidus are UMMZ 126680 (from 20 km NNE Caranavi, in La Paz department) and UMMZ 156014 (from 1 km E La Embocada, in Beni department). The former is a subadult whose lack of supraorbital beading is possibly due to immaturity, but whose lack of a postorbital constriction more closely resembles the material we refer to M. noctivagus (see below). UMMZ 156014, however, is an example of M. bishopi (see above). The only additional material that Anderson referred to M. impavidus consists of MSB 57000 (from Independencia in Pando department) and MSB 58508 (from 2 km S Caranda in Santa Cruz department); both are examples of ‘‘ Gracilinanus ’’ unduaviensis, a taxon that is currently treated (e.g., by Gardner, 1993) as a junior synonym of G. agilis .

BOLIVIAN SPECIMENS EXAMINED: Pando, Palmira ( MSB 57002).