Micoureus demerarae (Thomas)

VOSS, ROBERT S., LUNDE, DARRIN P. & SIMMONS, NANCY B., 2001, The Mammals Of Paracou, French Guiana: A Neotropical Lowland Rainforest Fauna Part 2. Nonvolant Species, Bulletin of the American Museum of Natural History 2001 (263), pp. 1-236 : 52-61

Micoureus demerarae (Thomas)

VOUCHER MATERIAL: AMNH 266428 , 266429 , 266431–266434 , 267370 , 267371 , 267818 ; MNHN 1995.911 – 1995.914 . Total = 13 specimens .

IDENTIFICATION: Although our voucher material corresponds closely to Tate’s (1933) and Husson’s (1978) descriptions of this taxon, the coloration of the ventral pelage and of the tail are variable among Paracou specimens and merits comment. Most of the ventral surface is covered by gray­based fur that

TABLE 11

Measurements (mm) and Weights (g) of Adult Metachirus nudicaudatus from French Guiana

is heavily washed with buff, but self­colored (pure buff) hairs cover the groin and throat, and a few specimens have narrow streaks of pure buff fur along the midline of the chest or abdomen. The tails of most Paracou specimens have white tips or are mottled with large white spots distally, but two adults (AMNH 267370, 267818) have entirely dark tails.

The holotype (BMNH 5.11.1.25) and other adult specimens from Guyana that we measured for comparison exhibit broad morphometric overlap with our vouchers (table 12). Additionally, fresh Guyanese skins (e.g., ROM 103370, 104708) are indistinguishable in coloration from our Paracou material. Thus, although several valid taxa may eventually be recognized among the many names currently synonymized with Micoureus demerarae (see below), the Paracou population can be confidently assigned to this species, and to the nominate race if a trinomial nomenclature is warranted.

Juveniles of Micoureus demerarae somewhat resemble Marmosa murina in size and external appearance, and the two species might therefore be confused in the field, even with specimens in hand. Based on our ma­ terial, the best external characters for discrimination are tail color (most, but not all, examples of M. demerarae have tails blotched or tipped with white, whereas M. murina has consistently all­dark tails), fur texture (longer and woolly in M. demerarae , close and smooth in M. murina ), the extent of fur at the base of the tail (conspicuously greater in M. demerarae than in M. murina ), and size of the manual claws (extending beyond the fleshy apical pads in M. demerarae but not in M. murina ).

REMARKS: Originally described as a subspecies of Marmosa cinerea by Thomas (1905), demerarae was treated as a distinct species of the cinerea group in Tate’s (1933) monographic revision of Marmosa (sensu lato). Cabrera (1958), however, considered demerarae to be a subspecies of cinerea , citing doubts that Tate (1939: 164, footnote 2) expressed about his own prior classification. The current allocation of Tate’s cinerea group to Micoureus follows Gardner and Creighton (1989). Among the many nominal taxa now synonymized with Micoureus demerarae (sensu Gardner, 1993) are several that Tate (1933) recognized as full species, all or some of which may yet prove to be valid (Patton et al., 2000). With the extensive series of specimens now available to evaluate the taxonomy of this widespread complex, the group is ripe for modern revisionary treatment.

OTHER SPECIMENS EXAMINED: Guyana — ‘‘R. Demerara’ ’ ( BMNH 7.6.20.14) ; Cuyuni ­ Mazaruni , Kartabo ( AMNH 42887 , 64156 ) ; Potaro ­Siparuni , 5 km SE Surama ( ROM 103146 ), Iwokrama Reserve ( ROM 104708 ) ; Upper Demerara ­Berbice , Comackka on Demerara River ( BMNH 5.11 .1.25 [holotype]), Tropenbos ( ROM 103370 ) ; Upper Takutu ­ Upper Essequibo , Achamere Wan ( ROM 34514), Ireng Valley ( BMNH 3.4.6.10), Kuitaro River 40 mi E Dadanawa ( ROM 35453), Weri More ( ROM 33201) .

FIELD OBSERVATIONS: All of our definite records of Micoureus demerarae at Paracou are based on collected specimens; of these, eight were shot, three were caught in Victor traps, and two were caught in elevated platform traps. Most (12) of our specimens were taken 1–17 m above the ground on lianas or in trees, but one juvenile was found climbing

TABLE 12 Measurements (mm) and Weights (g) of Adult Micoureus demerarae

among dead branches at ground level in a treefall. Five specimens were collected in well­drained primary forest, one in swampy primary forest, and seven in more­or­less disturbed habitats (roadside secondary growth and selectively logged forest).

Our single adult female specimen, collect­ ed on 12 August, was not carrying suckling young.

Monodelphis brevicaudata (Erxleben) Figures 29–31

VOUCHER MATERIAL: AMNH 267000. Total = 1 specimen.

IDENTIFICATION: The genus Monodelphis has never been revised, and many aspects of the currently accepted species­level taxonomy of these short­tailed opossums (summarized by Gardner, 1993) remain untested by substantive analyses of specimen data. To determine the correct identification of our single Paracou voucher, we examined comparative series, types, and original descriptions of all relevant taxa. Our resulting systematic conclusions broadly overlapped those of the late C. O. Handley, Jr., who generously shared with us the unpublished results of his previous research with many of the same specimens that we studied. His suggestions prompted us to reexamine some of our earlier ideas about character variation in the M. brevicaudata complex, and the following account therefore reflects his critical input.

Among the many named forms of redflanked Monodelphis currently synonymized with M. brevicaudata (see Gardner, 1993) are several readily diagnosable taxa that we provisionally recognize as full species. As understood by us, M. brevicaudata is restricted to the Guiana subregion of Amazonia (fig. 28) and is distinguished from other species of the brevicaudata complex, all of which are allopatric, by the extension of body fur onto the proximal one­third or more of the caudal dorsum; the ventral surface of the tail is just furred at the base (fig. 29). By contrast, only the basal one­sixth or less of the tail is furred, to about the same extent above and below, in M. palliolata (which occurs west of the Orinoco in northern Venezuela and northeastern Colombia), M. glirina (south of the Amazon and west of the Xingu), and in an unnamed form (a subspecies of M. brevicaudata in the view of C. O. Han­ dley, Jr., personal commun.) distributed south of the Amazon and east of the Xingu. In addition, whereas M. palliolata and M. glirina have orange ventral fur (not sharply differentiated from the color of the flanks) and a broad cap of grizzled­grayish fur extending across the crown of the head between the eyes, fully adult specimens of M. brevicaudata have whitish, cream, or buffy ventral fur (sharply differentiated from the reddish flanks) and a narrower cap of grizzled­grayish fur that (when present) is confined middorsally by a broad band of red above each eye. Monodelphis palliolata and M. glirina are externally similar, but differ in size (upper molar row ± 7.9 mm in palliolata , ± 7.9 mm in glirina ). The unnamed form south of the Amazon and east of the Xingu resembles geographically adjacent populations of M. brevicaudata (from Amapá and the eastern Guianas) in size and coloration but lacks the dorsal extension of body fur onto the tail.

Thus restricted, Monodelphis brevicaudata includes the following nominal taxa: brevicaudata Erxleben ( 1777) , brachyuros Schreber (1778) , touan Shaw (1800) , tricolor Geoffroy (1803) , hunteri Waterhouse (1841), orinoci Thomas (1899b), and dorsalis Allen (1904). The material we examined exhibits considerable geographic variation in pelage color, the taxonomic significance of which is difficult to evaluate. Possibly, pelage color may reflect species­level divergence that is not apparent in craniodental characters, but the material currently available is insufficient to determine whether chromatic variation is clinal or discontinuous. The following observations are intended to establish which of the above names is applicable to the coat­color phenotype represented by our Paracou voucher, not to revise the nomenclature of the entire brevicaudata complex, a task beyond the scope of this report.

Erxleben’s ( 1777) description of Didelphis brevicaudata and Schreber’s (1778) description of Didelphys brachyuros were both based on Seba’s (1734: 50) description and illustration (op. cit.: pl. xxxi, fig. 6) of ’’ Muris sylvestris Americani faemina ’’. Seba’s original specimen (BMNH 67.4.12.540; see Thomas, 1892) is therefore the type of both brevicaudata and brachyuros , so these nominal taxa are objective synonyms (for the priority of Erxleben’s name see Thomas, 1888: 356). We examined BMNH 67.4.12.540, an adult female preserved in fluid with an extracted skull. Despite more than two centuries in preservative, this specimen is in re­ markably good condition and the apparently unfaded pelage is distinctly bicolored (reddish dorsally and abruptly paler ventrally), exactly as described by Seba, Erxleben, and Schreber; there is no middorsal stripe of grizzled­brownish, ­grayish, or ­blackish fur. Although Matschie (1916) restricted the type locality of Monodelphis brevicaudata to Surinam, bicolored specimens resembling the type are only known from the interfluvial region between the lower Caroni­Orinoco and the lower Mazaruni­Essequibo in northeastern Venezuela and northwestern Guyana (fig. 28). Because Matschie’s restriction was obviously erroneous, we hereby emend the type locality to the vicinity of Kartabo, Cuyuni­ Mazaruni District, Guyana (locality 15 in fig. 28), from which a well­preserved bicolored specimen (AMNH 48133) closely resembling the type was collected by William Beebe in 1919 .8

By contrast with the limited geographic distribution of bicolored animals, tricolored specimens of Monodelphis brevicaudata have been collected throughout French Guiana, Surinam, Guyana, Guianan Venezuela (south and east of the Orinoco), and Guianan Brazil (north of the Amazon and east of the Rio Negro). In fully adult examples of this coat­color phenotype, a broad middorsal stripe of grizzled­brownish, ­grayish, or ­blackish fur is sharply set off from the clear (ungrizzled) reddish flanks, which are separated by a similarly abrupt transition from the pale (whitish, cream, or buffy, but sometimes partly gray­based) ventral fur. Whereas tricolored skins from Brazil and the Guianas are often brightly colored (with blackish or grayish middorsal stripes and cream or whitish venters), most tricolored Venezuelan skins have brownish middorsal stripes and buffy venters that exhibit less chromatic contrast with the reddish flanks. Despite Husson’s (1978) remark that his Surinamese specimens represented a full range

8 Kyk­over­al, a small island opposite Kartabo at the confluence of the Cuyuni and Mazaruni Rivers, was the seat of government of the Dutch colony of Essequibo from the early 1600s until 1740 (Beebe, 1925). The environs of Kartabo (Kartabu Point on recent maps; 6°23̍N, 58°41̍W) are therefore a plausible source of some of the South American material assembled by Albert Seba (b.1665, d.1736; Engel, 1937) in Amsterdam.

of intermediates between the bicolored and tricolored phenotypes, all of the Surinamese specimens we examined (including Husson’s material, obtained on loan from the RMNH) are tricolored.

The oldest available name for any tricolored form of Monodelphis brevicaudata is Viverra touan Shaw (1800) , which was based on Buffon’s (1789) description of ‘‘Le Touan’’ from Cayenne. 9 That the name touan properly applies to the tricolored phenotype is unambiguously supported both by Buffon’s and Shaw’s explicit mention of a blackish middorsal stripe extending from the rostrum to the base of the tail, and by the fact that only tricolored animals are known from French Guiana. The appropriate trinomial, if one is needed, for our Paracou voucher is therefore M. b. touan . Unfortunately, the application of the name touan has been a persistent source of confusion in the literature. Thomas (1888) and Cabrera (1919) regarded touan as a synonym of brevicaudata , but Cabrera (1958) listed touan (without comment) as a distinct species that included such divergent forms as emiliae , paulensis, and rubida as subspecies. Current usage (Gardner, 1993) recognizes M. emiliae , M. rubida , and M. sorex (including paulensis) as full species that can be distinguished from M. brevicaudata by trenchant craniodental characters (e.g., those described by Pine and Handley, 1984).

In a recent treatment of Venezuelan Monodelphis, Linares (1998) inexplicably reversed the application of touan and brevicaudata by assigning the former name to the bicolored phenotype and the latter name to tricolored animals (including M. palliolata ). According to Linares, touan and brevicaudata are distinguished by craniodental characters in addition to pelage color pattern, and occur sympatrically in northeastern Venezuela, the Guianas, and in the Brazilian state of Para´. However, specimens referable to touan and brevicaudata are not craniodentally dif­

9 Didelphis tricolor E. Geoffroy is another name proposed for ‘‘Le Touan’’, but it is based on a different specimen in the Paris museum than that illustrated and described by Buffon (Geoffroy, 1803). The type of tricolor (MNHN 1990.421), like Buffon’s lost specimen, was apparently collected by M. de la Borde of Cayenne (Julien­Laferrière, 1994).

(= Monodelphis brevicaudata ). All views approximately Χ2.

ferentiated in our experience, nor have we seen evidence that two species assignable to the brevicaudata complex are sympatric anywhere. Linares also resurrected Cabrera’s (1958) hypothesis that touan and emiliae are conspecific, but our observations support Pine and Handley’s ( 1984) conclusion that emiliae is a distinctive species with no special similarity to touan or to other members of the brevicaudata complex.

In order to definitively resolve these conflicting usages, we hereby designate FMNH 21720 as the neotype of Viverra touan Shaw. The neotype, consisting of the skull (fig. 30) and the tricolored skin (fig. 31) of an adult male, was collected by S. Klages at Cayenne, French Guiana, on 26 February 1917.

Despite the conspicuous geographic variation in pelage color within Monodelphis brevicaudata noted above, we are not persuaded of the necessity for a formal trinomial nomenclature. Although the brevicaudata and touan phenotypes are clearly distinct in Guyana, some bicolored Venezuelan specimens from NE Bolívar (e.g., EBRG 17536, USNM 385004, 385005) have indistinctly grizzled middorsal fur, somewhat resembling the middorsal pigmentation of drab­tricolor skins from Amazonas and southeastern Bolívar, an observation that could be interpreted as evidence that bicolored and tricolored populations intergrade clinally in Guianan Venezuela. Furthermore, although our samples of measurable adults are too small for

TABLE 13 Measurements (mm) of Adult Monodelphis brevicaudata a

confident statistical inference (table 13), no morphometric differences are apparent between bicolored and tricolored animals to suggest that these are anything more than local coat­color variants. Larger series of specimens, especially from western Guyana and eastern Venezuela, together with molecular data would be helpful in any future effort to evaluate the taxonomic significance of pelage color variation in this species.

BICOLORED SPECIMENS EXAMINED: Guyana — Cuyuni ­ Mazaruni, First Falls on the Cuyuni River ( BMNH 34.6.30.65), Kartabo ( AMNH 48133 ) ; Essequibo Islands ­ West Demerara, Buck Hall ( BMNH 17.7.7.1). Venezuela — Bolívar, 65 km SSE El Dorado ( USNM 385005 ), 56 km SE El Manteco ( USNM 385004 ), Reserva Forestal Imataca ( EBRG 17536 ). Without locality data — ( BMNH 67.4 .12.540 [holotype of brevicaudata ], 88.1.31.1 [holotype of hunteri]) .

TRICOLORED SPECIMENS EXAMINED: Brazil — Amapa´, Serra do Navio (USNM 392050, 392051, 393424, 393428, 393430, 393435, 393436, 393438, 393439, 393441, 461434, 461435); Amazonas, Faro (AMNH 93972–93974, 94161, 94221), 80 km N Manaus (USNM 579976–579979), Santo Antonio da Amatary (AMNH 92879); Para´, Cachoeira Porteira (USNM 546209– 546219), ‘‘Serra do Tumucumaque’’ (USNM 392044–392049). French Guiana —Arataye (USNM 578009), Cacao (MNHN 1981.168, 1981.412, 1981.414–1981.416, 1982.599), Cayenne (FMNH 21720 [neotype of touan ], MNHN 1990.421 [holotype of tricolor ]), Montjoly (MNHN 1994.122), St.­Eugène (MNHN 1995.205, 1995.3216), Sophie (MNHN 1966.1, 1966.2), Tamanoir (FMNH 21793), Trois Sauts (MNHN 1981.413). Guyana —‘‘River Supinaam’’ (BMNH 10.9.29.26, 10.9.29.27); Cuyuni ­Mazaruni, Bartica Grove (BMNH 10.11.10.20), Kamakusa (AMNH 140465, 140466); Potaro ­ Siparuni, Anundabaru (AMNH 75830, 75831), Minnehaha Creek (AMNH 36317), Potaro (BMNH 12.6.9.9); Upper Demerara ­ Berbice, Dubulay Ranch (AMNH 267744, 268060, 268061). Surinam — Brokopondo, Brownsberg (CM 52729, RMNH 23403, 23404), Finisanti (FMNH 95338); Marowijne, 3 km SW Albina (CM 76730), Langa­ mankondre (RMNH 18227), 10 km N and 24 km W Moengo (CM 52730), Oelemarie (CM 76731, 76732), Paloemeu Airstrip (FMNH 94018, 94019); Nickerie, Avanavero (CM 68358), Kayserberg Airstrip (CM 68359), King Frederick William Falls (FMNH 48416); Saramacca, La Poule (FMNH 95339), Raleigh Falls (CM 63510, 63511, 68361); Suriname, Cultuurtuin near Paramaribo (RMNH 18076), Jarikaba near Uitkijk (RMNH 20672), Plantage De Morgenstond near Paramaribo (RMNH 17223), Plantation Clevia near Paramaribo (RMNH 21654). Venezuela — Amazonas, Boca Río Ocamo (AMNH 78093–78095), Esmeralda (AMNH 77281, 77282, 77287, 77288), Mt. Duida (AMNH 77283–77285, 77289, 77290–77296), ‘‘Río Casiquiare’’ (AMNH 77286, 78096–78100), Serra de Neblina (AMNH 244469); Bolívar, Arabupu (AMNH 75681–75687), Auyantepui (AMNH 130516, 130560–130565, 130573–130576, 130727), Caicara (BMNH 98.12.1.22 [holotype of orinoci]), Ciudad Bolívar (AMNH 16124– 16126 [type series of dorsalis].

FIELD OBSERVATIONS: The single example of Monodelphis brevicaudata that we collected at Paracou is a partially eaten specimen caught in a Victor trap set under a fallen tree (fig. 32) in well­drained primary forest. Several additional specimens were previously taken by O. Henry in the course of his multiyear trapping study (G. Dubost, personal commun.), but we have not examined his material.

Figures

Fig. 29. Distribution of body pelage on tails of Monodelphis brevicaudata (A, AMNH 93972) and M. palliolata (B, AMNH 69942). In brevicaudata, body fur extends onto the caudal dorsum for onethird or more of the length of the tail, but the caudal ventrum is only furred at the base. In palliolata and other taxa formerly synonymized with brevicaudata, the base of the tail is furred to about the same extent above and below. Both views about Χ1.2.

Fig. 30. Dorsal, ventral, and lateral cranial views of FMNH 21720, neotype of Viverra touan Shaw

Fig. 31. Dorsal, lateral, and ventral views of the skin of FMNH 21720, neotype of Viverra touan Shaw (= Monodelphis brevicaudata). All views approximately life­size.