Marmosops (Marmosops) soinii, Voss & Fleck & Jansa, 2019

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 : 61-68

Marmosops (Marmosops) soinii , new species

Figures 20–22 , 23A

HOLOTYPE: MUSM 13284, an adult male specimen collected by the first author (original number RSV 2114) on 1 June 1998 at Nuevo San Juan on the right bank of the Río Gálvez , Loreto department, Peru. The entire specimen was originally preserved in ethanol, but the skull was later extracted and cleaned. The holotype is additionally represented by frozen tissues in the Ambrose Monell Cryo Collection (AMNH), from which Díaz-Nieto et al. (2016) obtained a nearly complete (1148 bp) cytochrome b sequence (GenBank: KT437848 ) and a shorter (882 bp) fragment from exon 11 of the nuclear BRCA1 gene ( KT454025 ).

OTHER VOUCHER MATERIAL (TOTAL = 24): Jenaro Herrera (AMNH 276714; MUSM 23804, 23805), Nuevo San Juan (AMNH 268215, 268216, 272709, 272760, 273050, 273078, 273151, 273189; MUSM 11040, 11046, 11047, 13285, 13286, 15298–15300, 15306, 15307), San Pedro (MUSM 22331; UF 30449, 30450).

OTHER INTERFLUVIAL RECORDS: None.

DISTRIBUTION: Known only from the Yavarí- Ucayali interfluve.

DESCRIPTION: A species of Marmosops conforming in all respects to the generic description provided by Díaz-Nieto and Voss (2016: 14–15), but distinguished from other congeneric taxa by the following combination of traits: Dorsal pelage (fig. 20) dull reddish-brown, somewhat resembling Ridgway’s (1912) Natal Brown or Olive Brown, but slightly paler. Ventral pelage (fig. 21) continuously self-cream from chin to groin, but this median color much narrowed between the fore- and hind limbs by broad lateral zones of gray-based fur. Tail very long (>140%, on average) and uniformly dark from base to tip dorsally, but indistinctly paler ventrally in some specimens. Hands and feet covered dorsally with mostly pale hairs, but sometimes indistinctly darker over the metapodials. Gular gland present in adult males and adult females. Lateral carpal tubercle present as an anteroposteriorly elongated knob in adult males. Forearm with one antebrachial vibrissa. Mammae 3–1–3 = 7 (e.g., AMNH 272709, 273189; MUSM 15300) or 4–1–4 = 9 (e.g., AMNH 273151), all abdominal/inguinal. Scrotum unpigmented, white.

Nasal bones conspicuously wider posteriorly (near the maxillary-frontal suture) than anteriorly, and long (extending posteriorly beyond the lacrimals). Lacrimal foramina concealed inside the orbit in some specimens, partially exposed to lateral view on the anterior orbital margin in others. Supraorbital margins smoothly rounded or with inconspicuous beading in juveniles, subadults, and young adult females (e.g., MUSM 15298, 15299), but distinctly beaded in older and larger adults, especially males (e.g., AMNH 272760, 276714; MUSM 11046), which also develop small postorbital processes (fig. 23A). Incisive foramina short, not extending posteriorly beyond the canine alveoli; maxillopalatine fenestrae long and narrow, usually extending from between the upper third premolars (P3s) to between the third molars (M3s); palatine fenestrae always present, usually as multiple holes on each side. Subsquamosal foramen short (as in other members of the nominotypical subgenus), not exposing the lateral surface of the petrosal

TABLE 25

behind the sulcus for the prootic sinus (Díaz- Nieto and Voss, 2016: fig. 9).

Upper canine (C1) simple, without accessory cusps in either sex. M3 anterior cingulum incomplete (preprotocrista terminates at base of paracone, not continuous with anterolabial cingulum). Unworn lower canine (c1) distinctly taller than first lower premolar (p1), sometimes with a small but distinct posterior accessory cusp. Entoconids small, neither as tall nor as bulky as adjacent paraconids.

COMPARISONS: This species, previously referred to as Marmosops “Gálvez,” was included in molecular analyses reported by Díaz-Nieto et al. (2016), who recovered it within a strongly supported monophyletic group (“Clade E”) that also included M. ocellatus Tate, 1931 , and M. “Juruá” (another unnamed form). Marmosops ocellatus —resurrected from synonymy and redescribed by Voss et al. (2004) —occupies deciduous, semideciduous, and riparian forests in the Cerrado landscapes of eastern Bolivia and southwestern Brazil ( Emmons et al., 2006; Cáceres et al., 2007; Semedo et al., 2013), whereas M. “Juruá” corresponds to the Amazonian species that Patton et al. (2000) called M. impavidus Tschudi, 1845 (a nomen dubium). 13 Comparisons with M. “Juruá” will be provided when that species is formally named in a subsequent publication. The following comparisons serve to distinguish M. soinii from M. ocellatus , its closest named relative as determined by Díaz-Nieto et al.’s (2016) results.

Marmosops soinii and M. ocellatus are morphometrically similar (table 25), with broad overlap in most measured dimensions (except male tail length). In qualitative comparisons (table 26), M. soinii differs from M. ocellatus by its reddish-brown dorsal pelage, which appears somewhat darker and more richly pigmented in side-by-side comparisons with the somewhat paler dorsal fur of the latter species (fig. 20). The wider lateral zones of gray-based fur in M. soinii are conspicuous in ventral pelage comparisons (fig. 21). Marmosops soinii has a relatively longer tail (about 147% of head-and-body length, on average) that is uniformly dark from base to tip, whereas the relatively shorter tail of M. ocellatus (about 136% of head-and-body length) is bicolored at its base (distinctly paler ventrally than dorsally) and particolored (paler distally than proximally, becoming completely unpigmented toward the tip in most examined specimens). Less conspicuously, a gular gland is present in adult males and at least some adult female specimens of M. soinii , whereas most examined adult specimens of M. ocellatus —the holotype (BMNH 28.2.9.87) is the unique exception—show no trace of glandular activity on the throat or upper chest. Lastly, adult female specimens of M. soinii have either 3–1–3 = 7 or 4–1–4 = 9 abdominalinguinal mammae, whereas M. ocellatus seems to consistently have 6–1–6 = 13 mammae (L.H. Emmons, personal commun.), of which the two anteriormost pairs are “thoracic” (sensu Tate, 1933), extending toward the lower chest from the 13 As explained by Díaz-Nieto et al. (2016), the epithet impavidus has been used for at least two distinct species, of which one has traits that are inconsistent with the original description, and the other is not known to occur near the type locality. The type is apparently lost, and it is not certain that the animal described by Tschudi was even a species of Marmosops .

abdominal/inguinal positions occupied by the more posterior teats.

These species are craniodentally similar, but specimens of M. ocellatus seem to lack any trace of supraorbital beading, and none that we examined has postorbital processes (fig. 23B). In almost all examined specimens of M. soinii the basisphenoid is concealed from lateral view in the rear of the orbit (AMNH 272760 is the unique exception), but the basisphenoid is laterally exposed through an expanded sphenorbital fissure in the rear of the orbit in M. ocellatus . 14

ETYMOLOGY: For Pekka Soini (fig. 24), legendary field biologist and visionary conservationist, who lived and worked in Loreto for many years and made important contributions to the

14 This interesting character, which is taxonomically useful in other genera and probably covaries with size of the optic nerve, was illustrated by Pavan and Voss (2016: fig. 8) for Monodelphis .

TABLE 26

herpetology and mammalogy of northeastern Peru ( Mittermeier et al., 2004).

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: Of the 23 specimens for which we have capture information, 13 were trapped, shot, or captured by hand while climbing on saplings, lianas, logs, or fallen branches at estimated heights from 0.2 to 1 m above the ground; only five are definitely known to have been captured on the ground (of which three were taken in pitfalls). Most (15) specimens were taken in primary upland forest, but four were in secondary forest (abandoned swiddens), two were in swampy primary forest, one was in primary floodplain forest, and one was captured in a house. Ten specimens were shot or captured by hand while active at night, and another 10 were found at dawn in traps that had been baited in the late afternoon of the previous day (three specimens found at dawn in pitfalls might have been taken at any time in the previous 24 hours).

SPECIMENS OF MARMOSOPS OCELLATUS EXAMINED (TOTAL = 23): Bolivia — Santa Cruz, 7 km SE Ariruma (AMNH 275461), 6 km W Ascención (AMNH 261265), Ayacucho (USNM 390571, 390572), Buenavista (BMNH 26.1.5.25 [holotype], 28.2.9.87, 28.2.9.90), El Refugio (USNM 584466, 584467, 584469), 3.5 km W Estación Pailón (AMNH 260026–260028), 7 km E and 3 km N Ingeniero Mora (AMNH 247652), Lago Caimán (USNM 581979), 2 km S Las Cruces (AMNH 263549), 10 km N San Ramón (AMNH 261266, 261267), 15 km S Santa Cruz (MSB 58512, 58513), Warnes (USNM 390022), 13 km N Zanja Honda (AMNH 275462). Brazil — Mato Grosso, 3 km W Cáceres on BR 30 (USNM 390026).

Figures

FIG. 20. Dorsal views of skins of Marmosops soinii (left to right: AMNH 272760, MUSM 15298, MUSM 23805) and M. ocellatus (left to right: USNM 584469, 584466, 584467).

FIG. 21. Ventral views of skins of Marmosops soinii (left to right: AMNH 272760, MUSM 15298, MUSM 23805) and M. ocellatus (left to right: USNM 584469, 584466, 584467).

FIG 22. Dorsal, ventral, and left lateral cranial views of Marmosops soinii (AMNH 276714). All views about ×2.5.

FIG. 23. Dorsal views of interorbital region of A, Marmosops soinii (AMNH 272760) and B, M. ocellatus (AMNH 261266).