Marmosops pakaraimae Voss et al., 2013

Díaz-Nieto, Juan F. & Voss, Robert S., 2016, A Revision Of The Didelphid Marsupial Genus Marmosops, Part 1. Species Of The Subgenus Sciophanes, Bulletin of the American Museum of Natural History 2016 (402), pp. 1-72 : 18-21

Marmosops pakaraimae Voss et al., 2013

Figures 11–13

Marmosops pakaraimae Voss et al., 2013: 6 (original description).

TYPE MATERIAL: The holotype (by original designation) consists of the skin, skull, postcranial skeleton, and preserved tissues of an adult male ( ROM 115129 ; original number F46739 ) collected by Burton K. Lim and Deirdre M. Jafferally on 26 February 2003 at “Second Camp” on Mount Roraima (fig. 10: locality 49), CuyuniMazaruni Region, Guyana. The other seven specimens listed below are all paratypes .

DISTRIBUTION, HABITATS, AND SYMPATRY: Marmosops pakaraimae is currently known from just five localities, of which three are in the Pakaraima Highlands of western Guyana and two are in the adjacent highlands of eastern Venezuela. Recorded elevations at these localities range from 800 m to about 1500 m above sea level, and recorded habitats are premontane or lower montane rain forest ( Voss et al., 2013). This species is not definitely known to occur sympatrically with any congeneric species, although it might be expected to come into contact with M. parvidens and/or M. pinheiroi at lower elevations in western Guyana or eastern Venezuela.

DESCRIPTION: Body pelage dark brown (near Dark Umber) middorsally, but indistinctly paler laterally, and about 8–9 mm long at midback; ventral pelage superficially whitish (the ventral coloration contrasting abruptly with the brownish flanks), but hairs of throat, chest, abdomen, and inner surfaces of fore- and hind limbs uniformly gray based (only the apex of the chin, the oral margins, and the scrotum have self-white fur). Manus covered dorsally with uniformly pale hairs in some specimens (e.g., ROM 114698), but metacarpals distinctly darker than digits in others (ROM 115129); lateral carpal tubercles spoon shaped in all examined adult males. Mammary formula unknown (no female specimens examined). Tail much longer than combined length of head and body (mean LT/HBL × 100 = 148%); dorsal caudal surface uniformly dark from base to tip, but ventral surface indistinctly paler (especially near the base of the tail).

Nasal bones long (consistently extending well behind the lacrimals) and much wider posteriorly than anteriorly (laterally expanded at the maxillary-frontal suture). Lacrimal foramina concealed from lateral view inside anterior orbital margin; zygomatic process of squamosal broadly overlapped dorsally by the jugal. Palatine fenestrae absent. Dorsolateral margin of ethmoid foramen formed by the orbitosphenoid.

Upper canine (C1) short, with anterior and posterior accessory cusps in males (female specimens are unknown). Upper third molar (M3) anterolabial cingulum narrowly continuous with preprotocrista (anterior cingulum complete). Lower canine (c1) premolariform (procumbent, with posterior accessory cusp) and small, subequal in height to p1; c1 anterolingual accessory cusp absent. Entoconid of m1 apparently subequal to adjacent m2 paraconid; 3 unworn m4 talonid with three distinct cusps.

COMPARISONS: Marmosops pakaraimae averages larger than M. parvidens in most measured external dimensions (table 2), and the two species differ strikingly in dorsal pelage coloration (dark brown in pakaraimae versus paler and distinctly reddish brown in M. parvidens ; Voss et al., 2013: fig. 2). The difference in ventral pel-3 This character is difficult to evaluate because specimens with unworn molars (juveniles and subadults) are unavailable.

age coloration (op. cit.: fig. 3) is even more striking: whereas M. pakaraimae has almost completely gray-based ventral fur, all examined specimens of M. parvidens have a continuous streak of self-whitish fur that extends from chin to groin. Marmosops pakaraimae is consistently larger than parvidens in all measured craniodental dimensions, especially in five variables (CBL, LIB, LPB, MTR, LM) that exhibit nonoverlapping variation between our male samples (no female specimens of M. pakaraimae are known). Side-by-side comparisons of representative skulls (figs. 11–13) reveal that M. pakaraimae has a visibly broader interorbital region but relatively smaller orbits than M. parvidens . In qualitative aspects of craniodental morphology, however, these species are notably similar, both having lacrimal foramina that are mostly concealed from lateral view inside the anterior orbital margin, upper third molars with narrowly complete anterior cingula, and consistently tricuspid m4 talonids.

Marmosops pakaraimae also averages larger than M. pinheiroi in most external dimensions, and the two species differ in dorsal pelage color (dark brown in M. pakaraimae versus paler brownish gray in M. pinheiroi ). The ventral fur of M. pakaraimae is also more extensively gray based than the ventral fur of M. pinheiroi , which usually includes a narrow, discontinuous midventral streak of selfwhite hairs. Marmosops pakaraimae is also larger on average than M. pinheiroi in craniodental measurements, especially in three dimensions (LIB, LPB, and LM) that exhibit nonoverlapping variation in our samples. Visual comparisons of representative skulls (figs. 11–13) reveal similar proportional differences between M. pakaraimae and M. pinheiroi to those previously noted between M. pakaraimae and M. parvidens , namely that M. pakaraimae has a relatively broader interorbit but smaller orbits. Additionally, the lacrimal foramina are more prominently exposed laterally, M3 never has a complete anterior cingulum, and m4 often has a bicuspid talonid in M. pinheiroi .

SPECIMENS EXAMINED (N = 8): Guyana — Cuyuni-Mazaruni, Mt. Roraima (ROM 115129, 115148, 115254); Potaro-Siparuni, Mt. Ayanganna (ROM 114698), Mt. Wokomung (ROM 115841, 115845). Venezuela — Bolívar, 85 km SSE El Dorado (USNM 385046), Churi-tepui (AMNH 176353).

Figures

FIG. 11. Dorsal views of skulls of the Parvidens Group of Sciophanes. Left to right: Marmosops pakaraimae (ROM 115129, holotype), M. parvidens (AMNH 267359), and M. pinheiroi (AMNH 267345). All views about ×3.

FIG.12. Ventral views of skulls of the Parvidens Group of Sciophanes. Left to right: Marmosops pakaraimae (ROM 115129, holotype), M. parvidens (AMNH 267359), and M. pinheiroi (AMNH 267345). All views about ×3.

FIG. 13. Lateral views of skulls and mandibles of the Parvidens Group of Sciophanes. Top to bottom: Marmosops pakaraimae (ROM 115129, holotype), M. parvidens (AMNH 267359 [skull], 267353 [mandible]), and M. pinheiroi (AMNH 267345). All views about ×3.