Marmosops parvidens ( Tate, 1931 )

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 : 21-25

Marmosops parvidens ( Tate, 1931)

Figures 2 , 5A , 7A , 11–13 , 14A

Marmosa parvidens Tate, 1931: 13 (original description).

Marmosa parvidens parvidens: Pine, 1981: 60 (name combination).

Marmosops parvidens: Gardner and Creighton, 1989: 4 (name combination).

TYPE MATERIAL: The holotype (by original designation) consists of the skin and skull of an adult female ( FMNH 18545 ; original number 8) collected by S.B. Warren on 8 September 1906 at Hyde Park (fig. 10: locality 50), a locality near sea level on the Demerara River in East Demerara– West Coast Berbice about 35 km south of Georgetown. No other specimens were mentioned in the original description of this species .

DISTRIBUTION, HABITATS, AND SYMPATRY: Examined specimens suggest that Marmosops parvidens occurs throughout most of the Guiana Region (north of the Amazon and east of the Rio Negro), but the species appears to be unknown from Venezuela ( García et al., 2014), and we have not examined any material from northern Pará. Although we have not personally examined material from Amapá, M. parvidens has recently been reported to occur there ( Silva et al., 2013). A single specimen is also known from SE Amazonia (on the lower Rio Tocantins, fig. 10: locality 13). All specimens associated with definite elevational data were collected between sea level and about 500 m. The predominant vegetation throughout the range of this species, which broadly overlaps that of M. pinheiroi , is lowland rain forest (e.g., in French Guiana, where both species occur sympatrically; Voss et al., 2001; Catzeflis et al., 2014).

DESCRIPTION: Body pelage dusty reddish brown (near Bister or Snuff Brown) middorsally, but indistinctly paler laterally, and about 6–8 mm long at midback; ventral pelage extensively self-white from chin to anus (including the inner surfaces of the fore- and hind limbs), usually with only narrow lateral-abdominal borders of gray-based fur. Manus covered dorsally with uniformly pale hairs (the metacarpals not contrasting sharply in color with the digits); lateral carpal tubercles spoon shaped in all examined adult males. Mammae 3–1–3 = 7 or 4–1–4 = 9. Tail much longer than combined length of head and body (mean LT/HBL × 100 = 150%); dorsal caudal surface uniformly dark from base to tip, but ventral surface indistinctly paler (especially near the base of the tail).

Nasal bones long (extending well behind the lacrimals) and much wider posteriorly than anteriorly (laterally expanded at the maxillary-frontal suture). Lacrimal foramina usually 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 usually formed by the orbitosphenoid.

Upper canine (C1) short, with anterior and posterior accessory cusps in both sexes. 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 subequal in height to adjacent m2 paraconid; unworn m4 talonid with three distinct cusps.

COMPARISONS: Marmosops parvidens is approximately the same size as M. pinheiroi (tables 2, 3) in external dimensions, and differences in dorsal pelage coloration (usually some shade of dusty reddish brown in M. parvidens versus dull brownish gray in M. pinheiroi ) are sometimes less than obvious. By contrast, ventral pelage coloration provides a consistently useful external criterion for separating these broadly sympatric species: whereas M. parvidens has a broad, continuous band of self-whitish fur that extends from chin to groin and along the inner surfaces of the fore- and hind limbs, M. pinheiroi has a much narrower, discontinuous midventral streak of self-white hairs that apparently never extends onto the throat nor along the inner surfaces of the fore- and hind limbs. Marmosops parvidens averages smaller than pinheiroi in most craniodental dimensions (WM 3 in males is the unique exception; tables 2, 3), but all measurements show overlapping variation between the two species, so none is diagnostic (despite unambiguous multivariate separation; Voss et al., 2001: fig. 24). Instead, qualitative aspects of craniodental morphology provide better characters for species identification: (1) whereas M. parvidens has lacrimal foramina that are usually concealed within the orbit (fig. 14A), the lacrimal foramina of M. pinheiroi are more prominently exposed laterally (fig. 14B); (2) the dorsolateral margin of the ethmoid foramen is usually formed by the orbitosphenoid in M. parvidens , whereas the corresponding bony margin in M. pinheiroi is often formed by the frontal; (3) the unworn M3 of M. parvidens has a narrowly complete anterior cingulum, whereas the anterolabial cingulum and preprotocrista of this tooth are discontinuous in M. pinheiroi ; (4) the talonid of m4 is consistently tricuspid in M. parvidens but often appears to be bicuspid in M. pinheiroi .

Comparisons between Marmosops parvidens and M. pakaraimae are provided in the account of the latter species (above).

REMARKS: The binomina “ Marmosa parvidens ” and “ Marmosops parvidens ” were previously applied to specimens of several distinct species, including M. bishopi , M. juninensis , M. ojastii , M. pakaraimae , and others (e.g., by Handley, 1976; Pine, 1981; Linares, 1998; Patton et al., 2000). The restricted sense in which this species is now understood was first defined by Voss et al. (2001). Current phylogeographic sampling of M. parvidens consists of 10 cytochrome- b sequences from six localities in French Guiana, Guyana, and Surinam; these differ from one another by an average uncorrected distance of just 1.6%, well below the threshold value for species recognition in coalescent analyses performed by Díaz-Nieto et al. (2016a). Additionally, we have not observed any geographic variation in morphology that corresponds to geographic variation in cytochrome- b sequence data from this species.

We carefully reexamined AMNH 97333, which remains the only specimen of Marmosops parvidens collected south of the Amazon. Although this specimen differs from material collected north of the Amazon in having the dorsolateral margin of the ethmoid foramen bordered by the frontal, and by lacking a continuous anterior cingulum on M3, it closely resembles typical M. parvidens in other respects, notably in its extensively self-white ventral pelage. Although molecular confirmation that M. parvidens occurs south of the Amazon would be welcome, we feel reasonably confident in the current identification of this unique specimen.

SPECIMENS EXAMINED (N = 42): Brazil — Amazonas, Boca Rio Paratucu ( AMNH 93970 ), 80 km N Manaus ( INPA 1758 , 1762–1769 , 1772–1779 ; USNM 579985–579989 ) ; Pará, Ilha do Taiuna ( AMNH 97333 ). French Guiana — Les Nouragues ( ISEM V-1633), Paracou ( AMNH 267344 , 267347 , 267348 , 267353 , 267359 , 267361 ; MNHN 1995-929 , 1995-933 , 1995-939 ), River Arataye ( USNM 548439 ). Guyana — Demerara-Mahaica, Hyde Park ( FMNH 18545 ), Upper Takutu–Upper Essequibo, Karanambo ( ROM 97938). Surinam — Brokopondo, Brownsberg Nature Park ( ROM 113997 , 114009 , 114144 ) ; Nickerie, Kayser Gebergte Airstrip ( FMNH 93169 ) ; Sipaliwini, Bakhuis Transect 13 ( ROM 117348 ) .

Figures

FIG. 2. Marmosops handleyi (above; photographed by J. Díaz-Nieto at Finca Costa Rica, Antioquia, Colombia) and M. parvidens (below; photographed by T. Semedo near Urucará, Amazonas, Brazil). In addition to obvious differences in body pelage color, these species differ in forefoot markings: whereas M. handleyi has dark metacarpal fur that contrasts with the pale fur of the manual digits, M. parvidens has all-pale forefeet.

FIG. 5. Ventral views of the palates of Marmosops parvidens (A, AMNH 267359), M. juninensis (B, AMNH 230016), and M. magdalenae (C, ICN 19926) illustrating species differences in the presence, absence, and morphology of palatal fenestrae and foramina. Abbreviations: if, incisive foramen; max, maxillary bone; mp, maxillopalatine fenestra; p, palatine fenestrae; pal, palatine bone; plpf, posterolateral palatine foramen; pre, premaxillary bone.

FIG. 7. Lateral view of anterior left lower dentition of Marmosops parvidens (A, AMNH 266425) and M. carri (B, KU 120254) illustrating species differences in lower canine (c1) morphology. In M. parvidens, c1 is subequal in height with the first lower premolar (p1), and it has a distinct posterior accessory cusp (pac). By contrast, c1 in M. carri is distinctly taller than p1 and lacks a posterior accessory cusp. Both illustrated specimens are males.

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.

FIG.14. Lateral views of the anterior orbital region of Marmosops parvidens (A, AMNH 267359) and M. pinheiroi (B, AMNH 267345) illustrating species differences in the lacrimal foramina (lf), which are usually concealed inside the orbit in M. parvidens, but which are laterally exposed on the orbital margin of M. pinheiroi.