Marmosa (Sciophanes), Diaz-Nieto et al., 2016

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 : 16-17

Subgenus Sciophanes Díaz-Nieto et al., 2016

TYPE SPECIES: Marmosops parvidens ( Tate, 1931) by original designation.

CONTENTS: Twelve species as described below.

DESCRIPTION: Combined length of head and body usually <120 mm and adult weight usually <30 g (except in Marmosops carri and M. fuscatus , both of which are substantially larger). Gular gland absent in all examined material. Lateral carpal tubercles consistently present in mature adult males; forearm with two widely separated antebrachial vibrissae. Mammae 3–1–3 = 7 or 4–1–4 = 9, all abdominal-inguinal (but note that mammary morphology is unknown for M. fuscatus , M. juninensis , M. ojastii , M. pakaraimae , and M. magdalenae ). Scrotal integument consistently unpigmented and covered with self-whitish fur.

Nasals laterally expanded at or near maxillaryfrontal suture (except in M. carri and M. fuscatus , which have very narrow, almost parallel-sided nasals). Interorbital region with rounded or squared supraorbital margins, without distinct beading and without distinct postorbital processes. Fenestra in parietal-squamosal suture consistently present; subsquamosal foramen anteroposteriorly elongate, exposing lateral surface of petrosal pars canalicularis behind sulcus for prootic sinus. Incisive foramina short, extending posteriorly between but not behind C1.

Upper canine (C1) with accessory cusps in one or both sexes (males of Marmosops carri and M. fuscatus lack C1 accessory cusps). Upper third molar (M3) with or without complete anterior cingulum (anterolabial cingulum and preprotocrista discontinuous in some species). Lower canine (c1) premolariform (procumbent, subequal in height to p1, and provided with a posterior accessory cusp) in most species (but not in males of M. carri and M. fuscatus , which have taller c1s that lack accessory cusps). Lower first molar (m1) entoconid and adjacent lower second molar (m2) paraconid subequal in height in some species, but m1 entoconid shorter than m2 paraconid in others.

COMPARISONS WITH THE NOMINOTYPICAL SUBGENUS: As explained by Díaz-Nieto et al. (2016a), species of Sciophanes can be unambiguously distinguished from species in the subgenus Marmosops by the morphology of the subsquamosal foramen (anteroposteriorly elongate in Sciophanes , anteroposteriorly constricted in Marmosops ; fig. 9), C1 accessory cusps (present in one or both sexes in Sciophanes , consistently absent in Marmosops ), and number of antebrachial vibrissae (two in Sciophanes , one in most Marmosops ). However, the two subgenera also differ in their modal expression of other characters. In particular, most species of Sciophanes are small (HBL usually <120 mm, weight usually <30 g), whereas most members of the nominotypical subgenera are substantially larger. There is some size overlap, however, because two species of Sciophanes ( M. carri and M. fuscatus ; see below) are large, and because some species in the nominotypical subgenus (e.g., M. ocellatus ; see Voss et al., 2004) are smaller than the subgeneric average. Nevertheless, wherever the two subgenera occur together (along the Rio Juruá, for example; Patton et al., 2000), species of Sciophanes are always smaller than sympatric members of the nominotypical subgenus.

Another potentially useful character for subgeneric identification is the morphology of the lower canine (c1), which is small (subequal in height to p1) and premolariform (with a well-developed posterior accessory cusp) in both sexes of most species of Sciophanes . By contrast, c1 is a larger tooth (always distinctly taller than p1) and often lacks a distinct posterior accessory cusp in members of the nominotypical subgenus. The noteworthy exceptions in this context are male specimens of the largest species of Sciophanes ( M. carri and M. fuscatus ), in which c1 is taller than p1 and lacks a distinct posterior accessory cusp.

Among external traits that are sometimes observed in the nominotypical subgenus, no spe- cies of Sciophanes has a gular gland, and none has dark-furred hind feet, “pectoral” mammae, or pigmented scrotal epithelium. Additionally, no species of Sciophanes has distinctly beaded supraorbital margins, develops postorbital processes, has long incisive foramina (extending behind the upper canines), or lacks a fenestra in the squamosal-parietal suture.

REMARKS: The monophyly of Sciophanes is strongly supported by taxon-dense phylogenetic analyses of both nuclear and mitochondrial genes ( Díaz-Nieto et al., 2016a, 2016b). Unfortunately, taxon-dense phylogenetic analyses incorporating morphological characters have yet to be completed, so it is not known which (if any) of the diagnostic external and craniodental traits described above might optimize as subgeneric synapomorphies.

The same molecular analyses that provided strong support for the monophyly of Sciophanes also recovered three well-supported species groups within this subgenus. Díaz-Nieto et al. (2016a: fig. 5) referred to these groups using alphabetical labels, for which we substitute other names in this report: the Fuscatus Group (for “clade A,” including Marmosops carri , M. fuscatus , M. handleyi , and M. invictus ), the Bishopi Group (for “clade B,” including M. bishopi , M. juninensis , M. ojastii , and two new species), and the Parvidens Group (for “clade C,” including M. pakaraimae , M. parvidens , and M. pinheiro i). All three groups are morphologically diagnosable (table 1).