Marmosa (Micoureus) rutteri Thomas, 1924

Voss, Robert S., Giarla, Thomas C., Díaz-Nieto, Juan F. & Jansa, Sharon A., 2020, A Revision Of The Didelphid Marsupial Genus Marmosa Part 2. Species Of The Rapposa Group (Subgenus Micoureus), Bulletin of the American Museum of Natural History 2020 (439), pp. 1-60 : 1-60

Marmosa (Micoureus) rutteri Thomas, 1924

Marmosa rutteri Thomas, 1924: 536 (original description).

Marmosa germana rutteri: Tate, 1933: 81 (name combination).

Marmosa (Marmosa) germana rutteri: Cabrera, 1958: 15 (name combination).

Micoureus regina: Gardner, 1993: 20 (part; rutteri treated as synonym); not regina Thomas, 1898 .

Micoureus regina germanus: Gardner and Creighton, 2008: 81 (part; rutteri treated as synonym); not germana Thomas, 1904 .

Marmosa (Micoureus) regina: Voss and Jansa, 2009: 101 (part, rutteri treated as synonym); not regina Thomas, 1898 .

TYPE MATERIAL: The holotype (by original designation, BMNH 24.2.22.67) consists of the skin and skull of an adult male collected by Latham Rutter on 10 September 1923 at “Tushemo, near Masisea” at an elevation of 1000 ft [305 m] in the Peruvian department of Ucayali.

DISTRIBUTION AND SYMPATRY: Marmosa rutteri is a lowland Amazonian species that has been collected at or below about 800 m in southeastern Colombia, eastern Ecuador, eastern Peru, and western Brazil. It is known to occur sympatrically with several other members of the subgenus Micoureus , including M. constantiae (south of the Amazon in western Brazil and eastern Peru), M. germana (north of the Amazon in eastern Peru and eastern Ecuador), and an undescribed species (M. “Yasuni”; see above) that appears to have much the same geographic distribution as M. germana .

DESCRIPTION: The dorsal pelage of Marmosa rutteri ranges in color from a dull grayish hue (near Ridgway’s Deep Grayish Olive) to paler, more yellowish tones (close to Light Brownish Olive or even to Isabella Color); at midback the fur ranges in length from 8 to 16 mm, with longer fur typically in foothill material, but in most specimens we measured the middorsal fur is 9–11 mm long. The ventral pelage, at least along the midline from chin to groin, is usually selfyellowish (e.g., Antimony Yellow or Colonial Buff), although there are often broad lateral zones of gray-based fur on the lower thorax and abdomen (between the fore- and hind limbs), and a few skins have mostly gray-based ventral fur with self-yellowish fur only on the chin, throat, and groin. The tail is approximately 145% of head-and-body length, on average, and only a short part of the base (usually <20 mm) is covered with fur; the naked, scaly part of the tail is completely dark (grayish or grayish brown in life), and it is not marked with white in any specimen that we examined.

Adult skulls ( fig. 13C, F ) have short, wide rostrums and broadly flaring zygomatic arches. The postorbital processes, even of most young adults, are large and triangular. The maxillo-

palatine fenestrae extend from the level of M1 to the level of M 3 in most specimens, but in many others they extend only from M1 to M2; however, these openings are seldom very wide, usually taking the form of narrow, bilaterally paired slits. Palatine fenestrae are bilaterally absent in most specimens, but small openings in the posterior palate are present unilaterally (e.g., in fig. 13F ) and sometimes bilaterally in others. The first three upper molars (M1–M3) have long postprotocristae, and posterior cingulids are often distinct on m1–m3 (but always, at least, on unworn m2).

VARIATION: Summary statistics for external and craniodental measurements of Marmosa rutteri are provided in table 9 , and qualitative trait variation is summarized in table 10 . None of the morphometric or qualitative variation in this species seems particularly noteworthy, nor does this variability appear to be geographically structured. For example, we observed broad morphometric overlap between samples collected north and south of the upper Amazon. Although a few populations exhibit high frequencies of unusual phenotypes (e.g., 6 out of 10 specimens that we scored for ventral fur color from Amazonas

department, Peru, had mostly gray-based ventral fur), we interpret these as evidence of geographic variation in a single, widespread species.

COMPARISONS: Comparisons of Marmosa rutteri with other members of the Rapposa Group are provided in the preceding accounts. Marmosa rutteri differs from other (non-Rapposa Group) species of the subgenus Micoureus with which it is sometimes sympatric (e.g., M. constantiae and M. germana ) by its long postprotocristae on M1–M3, and by the presence of posterior cingulids on unworn m2 (and sometimes other lower molars); it is also substantially larger than the undescribed species of the Perplexa Group with which it cooccurs north of the Amazon (M. “ regina ” sensu Hice and Velazco, 2012). Additional comparisons between M. rutteri and M. constantiae were summarized by Voss et al. (2019: 27–29).

HABITATS: The entire known geographic range of Marmosa rutteri is in western Amazonia, where the predominant natural climax vegetation is lowland rainforest. However, Amazonian vegetation is notoriously heterogeneous, including numerous distinct kinds of habitats, especially in riparian landscapes ( Prance, 1979; Pires and Prance, 1985; Puhakka and Kalliola, 1995). Given that several species of the subgenus Micoureus have overlapping distributions in this region (see Distribution and sympatry, above), it would be reasonable to expect that some of them might be habitat specialists.

The most compelling evidence for habitat specialization by Amazonian species of Marmosa comes from an exemplary trapping study along the Rio Juruá in western Brazil ( Patton et al., 2000). At numerous sites along this major white- water river, Marmosa rutteri (“ Micoureus regina ”) and M. constantiae (“ Micoureus demerarae ”) were found to occur sympatrically, although usually not syntopically. Equal numbers of both species (N = 55 each) were collected. Of these, specimens of M. rutteri were trapped in both várzea (seasonally flooded forest; fig. 18 ) and terra firme (unflooded) habitats, whereas M. constantiae was taken almost exclusively in terra firme (unflooded) forest.

A similar pattern of habitat segregation is suggested by less extensive trapping results from Cuzco Amazónico on the left (north) bank of the Río Madre de Dios, another major whitewater river, in southeastern Peru (appendix 3: locality 71). Here, M. rutteri was taken in approximately equal numbers in both terra firme forest and in seasonally flooded vegetation, whereas most specimens of M. constantiae were taken in terra firme forest ( table 11 ). Based on these results, it seems plausible that M. rutteri might be a várzea specialist or, at least, might utilize seasonally flooded habitats to a greater extent than sympatric congeners. 8

The same two field studies also provide the best available data about microhabitat occupancy by Marmosa rutteri . In Patton et al.’s (2000) study, substantial numbers of traps were set on the ground and in trees at each sampled site along the Rio Juruá; all of the 55 specimens of M. rutteri they collected were taken in arboreal traps

8 In the commonly accepted terminology for Amazonian riparian vegetation ( Prance, 1979), várzea refers to forests seasonally flooded by sediment-bearing (white-water) rivers, whereas igapó refers to forests seasonally flooded by sedimentfree black- or clear-water rivers.

set 5–10 m above the ground, or were shot from arboreal perches> 2 m above ground level. At Cuzco Amazónico, 20 out of 24 specimens of M. rutteri (ca. 83%) were trapped in trees ( Woodman et al., 1995). These results are consistent with the commonly accepted notion that species of Marmosa are predominantly arboreal ( Charles-Dominique et al., 1981; Miles et al., 1981; Vieira and Monteiro-Filho, 2003).

SPECIMENS EXAMINED (N = 98): Brazil — Acre, Igarapé Porongaba (MVZ 190332), Nova Vida (MVZ 190333); Amazonas, Boa Esperança (MVZ 190330, 190331), Igarapé Nova Empresa (MVZ 190321, 190323–190325), opposite Altamira (MVZ 190328, 190329), Penedo (MVZ 190319, 190320), Seringal Condor (MVZ 190326). Colombia — Amazonas, Leticia (USNM 536890); Caquetá, Tres Troncos ( FMNH 70964– 70966). Ecuador — Napo, “near the river Napo ” ( BMNH 34.9.10.234–34.9.10.237); Orellana, San José de Payamino ( FMNH 124613); Sucumbíos, Boca Río Lagartococha (AMNH 72008, 72009). Peru — Amazonas, La Poza (MVZ 157629), mouth of Río Cenepa (AMNH 98712), vicinity of Huampami (MVZ 153278, 154749, 154751, 154755, 154758, 154762, 154764, 154766, 157628, 157630, 157631), vicinity of Kayamas (MVZ 153281); Ayacucho, Santa Rosa on Río Santa Rosa (LSUMZ 15674); Cuzco, Quincemil ( FMNH 75100); Loreto, Boca Río Curaray (AMNH 71951, 71956, 71958, 71964, 71966, 71968, 71975, 72010), Nuevo San Juan (AMNH 273164; MUSM 11055, 11063, 15315, 15316), Orosa (AMNH 74087), Otorongo (MUSM 33443), Pampa Chica ( FMNH 87118), San Antonio (AMNH 98655), San Jerónimo ( BMNH 28.5.2.231–28.5.2.241; FMNH 46110, 46111), Sarayacu (AMNH 76302, 76303), “Triunfo Chacras” (TTU 124799), Yurimaguas ( FMNH 19635); Madre de Dios, Blanquillo (MUSM 8399), Reserva Cuzco Amazónico (KU 144091, 144093, 144095, 144100, 144102, 144107, 144110, 144111; MUSM 6083, 6086–6088, 6090–6092, 6100, 6101), 30 km above mouth of Río Tambopata (USNM 530907); Pasco, San Pablo (AMNH 230019, 230021); Ucayali, Tushemo ( BMNH 24.2.22.67 [holotype]), Yarinacocha ( FMNH 55467).

Figures

FIG. 13. Dorsal and ventral cranial views (×1.75) of Marmosa rapposa (A, D; AMNH 210398), M. parda (B, E; FMNH 24139), and M. rutteri (C, F; MVZ 190331). All specimens are adult males.

FIG. 18. Seasonally flooded forest (várzea) at Seringal Condor, on the left bank of the Rio Juruá, Amazonas state, Brazil (appendix 1: locality 25; photo by J.L. Patton). Sparse understory vegetation characterizes some várzea sites like this one, but dense stands of giant herbs such as Heliconia spp. (Heliconiaceae) and Costa spp. (Costaceae) can be common elsewhere (Prance, 1979).

Tables

TABLE 9 Measurements (mm) and Weights (g) of Marmosa rutteri

	BMNH 24.2.22.67a	Malesb	Femalesc
HBL	158d	184 ± 11 (164–203) 17	174 ± 16 (152–206) 15
LT	213d	260 ± 17 (227–291) 17	240 ± 16 (210–269) 15
HF	28d	29 ± 2 (25–33) 18	28 ± 2 (25–30) 18
Ear	23d	26 ± 2 (23–29) 18	25 ± 1 (23–28) 17
CBL	—	45.0 ± 2.0 (41.6–49.7) 25	42.7 ± 2.0 (39.6–46.5) 24
NL	18.1	20.2 ± 1.5 (17.4–23.0) 29	19.2 ± 1.2 (17.2–21.6) 20
NB	5.6	6.4 ± 0.6 (5.5–7.7) 32	6.1 ± 0.5 (4.8–6.9) 26
LIB	7.3	8.4 ± 0.6 (7.2–9.6) 31	8.0 ± 0.5 (7.3–9.2) 26
LPB	7.2	7.4 ± 0.6 (5.9–8.6) 31	7.4 ± 0.6 (6.4–8.2) 26
ZB	—	25.8 ± 1.5 (23.4–28.7) 28	24.6 ± 1.3 (22.4–27.4) 25
PL	22.8	25.0 ± 1.2 (22.5–27.6) 31	24.0 ± 1.0 (22.2–26.6) 25
PB	13.3	14.5 ± 0.7 (13.1–15.7) 29	14.4 ± 0.6 (13.4–16.2) 26
MTR	16.7	17.9 ± 0.8 (16.7–19.4) 31	17.5 ± 0.6 (16.7–18.8) 26
LM	8.6	9.0 ± 0.4 (8.3–9.8) 31	9.1 ± 0.3 (8.6–9.6) 26
M1–3	7.3	7.6 ± 0.3 (7.0–8.2) 32	7.7 ± 0.2 (7.2–8.1) 26
WM3	2.9	3.0 ± 0.2 (2.6–3.3) 32	3.0 ± 0.1 (2.7–3.2) 26
Weight	—	132 ± 30 (84–180) 17	105 ± 23 (63–151) 12

a Holotype.

b The sample mean plus or minus one standard deviation, the observed range (in parentheses) and the sample size based on measurements of the following series: AMNH 71958, 76302, 230021; BMNH 24.2.22.67, 28.5.2.231–28.5.2.235, 28.5.2.237, 28.5.2.240; FMNH 46110, 46111; KU 144110; MUSM 11055, 11063, 15316; MVZ 154749, 154755, 154762, 154764, 154766, 157629, 157630, 157631, 190319, 190320, 190323, 190329–190332.

c The sample mean plus or minus one standard deviation, the observed range (in parentheses) and the sample size based on measurements of the following series: AMNH 71951, 72009, 72010, 74087, 98655, 98712, 273164; BMNH 28.5.2.241; FMNH 19635, 55467, 70966, 75100, 87118, 124613; KU 144093, 144095, 144100, 144102, 144107; LSMUZ 15674; MUSM 6086, 6087; MVZ 154758, 157628, 190321, 190326.

d Measured by the British method.

TABLE 10 Qualitative Trait Frequencies for Marmosa rutteri

Self-colored ventral fur (N = 52)
continuous from chin to groin:	42 (81%)
discontinuous (gray-based on abdomen):	10 (19%)
Tail coloration (N = 50)
particolored (marked with white distally):	0 (0%)
all-dark:	50 (100%)
Maxillopalatine fenestrae (N = 55)
extend from P3 to M3:	1 (2%)
extend from P3 to M2:	1 (2%)
extend from M1 to M3:	39 (71%)
extend from M1 to M2:	13 (24%)
absent:	1 (2%)
Palatine fenestrae (N = 53)
bilaterally present:	7 (13%)
unilaterally present:	10 (19%)
absent:	36 (68%)
Posterior cingulids (N = 47)
distinct on m1–m3:	21 (45%)
distinct on m1 & m2 only:	10 (21%)
distinct on m2 only:	13 (28%)
absent/indistinct:	3 (6%)

TABLE 11 Habitat Occupancy by Sympatric Species of Marmosa (Micoureus) at Cuzco Amazónico in Southeastern Peru (Table entries are numbers of specimens trapped.)

	M. constantiae a	M. rutteri a	Totals
Zone 1b	5	6	11
Zone 2c	1	7	8
Totals	6	13	19

a Both species identified as “ Micoureus regina ” by Woodman et al. (1991, 1995). Only specimens that we examined are included in these counts.

b Trapping area located in terra firme forest ( Duellman and Koechlin, 1991).

c Trapping area located in seasonally flooded forest ( Duellman and Koechlin, 1991).