Marmosa mexicana Merriam, 1897

Part, Tate’, The Species In, Mexicana’, And, Closely, Mitis’ Sections And Other & Forms, Related, 2010, A Revision Of The Didelphid Marsupial Genus Marmosa, Bulletin of the American Museum of Natural History 2010 (334), pp. 1-83 : 23-37

Marmosa mexicana Merriam, 1897 Figure 16

Didelphys murina: Waterhouse, 1846: 508 . Part, not Didelphis murina Linnaeus, 1758 .

Didelphys murina: Alston, 1880: 200 .?Part, not Didelphis murina Linnaeus, 1758 .

Didelphys murina: Thomas, 1882b: 372 .

Didelphis (Micoureus) murina: Allen, 1890: 190 . Name combination.

? Didelphis (Micoureus) murina: Allen, 1893: 240 .

Didelphys [(Micoureus)] murina: Thomas, 1888: 343 . Part, not Didelphis murina Linnaeus, 1758 .

? Marmosa murina: Thomas, 1895 b: 58 . Name combination.

? Marmosa murina: Allen, 1897: 44 .

Marmosa murina mexicana Merriam, 1897: 44 . Type locality ‘‘Juquila, Oaxaca.’’

Marmosa mexicana: Bangs, 1902: 19 . Part; first use of current name combination.

[ Marmosa murina ] mexicana: Elliot, 1904: 6 .

Marmosa murina mexicana: Elliot, 1905: 2 .

Marmosa murina mexicana: Allen, 1908: 648 .

? Marmosa murina: Allen, 1908: 648 .

Marmosa murina mexicana: Allen, 1910: 92 .

Marmosa murina: Allen, 1910: 92 . Part, not Didelphis murina Linnaeus, 1758 .

Marmosa ruatanica Goldman, 1911a: 237 . Type locality ‘‘Ruatan Island, off the north coast of Honduras.’’

Marmosa mayensis Osgood, 1913: 176 . Type locality ‘‘Izamal, Yucatan, Mexico.’’

[ Didelphis (Marmosa) ] mexicana: Matschie, 1916: 270 . Name combination.

[ Didelphis (Marmosa) ] mayensis: Matschie, 1916: 270 . Name combination.

[ Didelphis (Marmosa) ] ruatanica: Matschie, 1916: 270 . Name combination.

Marmosa ruatanica: Elliot, 1917: 1 .

Marmosa mayensis Elliot, 1917: 3 .

Marmosa murina: Gaumer, 1917: 7 .

Marmosa mexicana savannarum Goldman, 1917: 108 . Type locality ‘‘Boqueron, Chiriqui, Panama.’’

[ Marmosa (Marmosa) ] mexicana mayensis: Cabrera, 1919: 37 . Name combination.

[ Marmosa (Marmosa) ] mexicana mexicana: Cabrera, 1919: 37 .

[ Marmosa (Marmosa) ] mexicana savannarum: Cabrera, 1919: 37.

[ Marmosa (Marmosa) ] ruatanica: Cabrera, 1919: 39 .

Marmosa mexicana zeledoni: Peters et al., 1929: 129 .

Marmosa ruatanica ruatanica: Tate, 1933: 124 .

Marmosa mexicana mexicana: Tate, 1933: 132 .

Marmosa mexicana mayensis: Tate, 1933: 132 .

Marmosa mexicana mayensis: Hershkovitz, 1951: 551 .

Marmosa mitis ruatanica: Hershkovitz, 1951: 551 . Name combination.

Marmosa mexicana: Handley, 1966: 755 .

Marmosa robinsoni ruatanica: Hall, 1981: 15 . Name combination.

Marmosa mexicana mayensis: Hall, 1981: 15 .

Marmosa mexicana mexicana: Hall, 1981: 15 .

Marmosa mexicana savannarum: Hall, 1981: 16 .

Marmosa mexicana: Honacki et al., 1982: 22 .

Marmosa robinsoni: O’Connell, 1983: 1 . Part, not Marmosa robinsoni Bangs, 1898 .

Marmosa mexicana: Alonso-Mejía and Medellín, 1992: 1 . Part.

Marmosa mexicana savannarum : Villa-R. et al., 1993: 80.

Marmosa mexicana: Gardner, 1993: 18 . Part.

Marmosa robinsoni: Gardner, 1993: 18 . Part, not Marmosa robinsoni Bangs, 1898 .

Marmosa mexicana: Emmons, 1997: 26 . Part.

Marmosa robinsoni: Emmons, 1997: 26 . Part, not Marmosa robinsoni Bangs, 1898 .

Marmosa mexicana: Reid, 1997: 47 . Part.

Marmosa robinsoni: Reid, 1997: 48 . Part, not Marmosa robinsoni Bangs, 1898 .

Marmosa mexicana: Nowak, 1999: 21 . Part.

Marmosa robinsoni: Nowak, 1999: 21 . Part, not Marmosa robinsoni Bangs, 1898 .

Marmosa mexicana: Voss and Jansa, 2003: 75 . Part.

Marmosa mexicana: Brown, 2004: 59 . Part.

Marmosa robinsoni: Brown, 2004: 65 . Part, not Marmosa robinsoni Bangs, 1898 .

Marmosa mexicana: Gardner, 2005: 9 . Part.

[ Marmosa mexicana ] mayensis: Gardner, 2005: 9 .

[ Marmosa mexicana ] savannarum: Gardner, 2005: 9.

[ Marmosa robinsoni ] ruatanica: Gardner, 2005: 9 .

TYPE MATERIAL: The holotype (by original designation, USNM 71526) is a young adult (age class 6) male specimen consisting of a skin and skull. Although the skin is in good condition, the skull lacks most of the upper incisors, and the posterior palatal region is slightly damaged.

TYPE LOCALITY: The holotype was collected by E.W. Nelson and E.A. Goldman on 28 February 1895 at ‘‘Juquila’’ (5 Santa Catarina Juquila , gazetteer entry 11; appendix), a town on the Pacific slopes of the Sierra Madre del Sur in southwestern Oaxaca, Mexico. According to Goldman (1951: 215), Juquila is at 5000 ft (1524 m) ‘‘near the frost line and just above the limits of coffee culture. The climate is cool and damp. Much fog and mist prevail, as shown by the moss on the trees on the north slopes of the adjacent hills and by the abundance of vegetation belonging to the temperate mountain flora.’’

MORPHOLOGICAL DIAGNOSIS: Midrostral fur pale, usually contrasting sharply with darker fur of crown; dark median rostral stripe absent or inconspicuous; dark facial mask usually extending posteriorly to contact base of ear; dorsal body pelage reddish brown; dorsal cover hairs 7–11 mm in length, guard hairs 9–14 mm; gray-based ventral pelage (covering the sides of chest, abdomen, and upper inguinal region, but sometimes also extending to the sides of neck and inner parts of arms and legs) with yellowish or orangish hair tips; self-colored ventral pelage (extending as a continuous median stripe of variable width from chin to anus) yellowish or orangish. Exposed skin of tail dark brown (indistinctly paler ventrally in some individuals), without any consistent pattern of scale arrangement (both spiral and annular patterns coexisting); 14–16 scales/cm on dorsal surface at caudal midlength; caudal scalehairs reddish brown or light brown, detect- able without magnification; central hair of each caudal-scale triplet as long as two scales (rarely 1.5 scales long). Gular gland present. Mammae 5–1–5 5 11 to 7–1–7 5 15. Lateral and medial carpal tubercles present in mature adult males; medial carpal tubercle in mature adult males long (reaching the base of the pollex) and unsegmented, without externally distinguishable proximal and distal segments.

Length of rostral process of premaxillae similar to I1 height. Orbitosphenoid-alisphenoid suture approximately twice as long as height of sphenorbital fissure in lateral view. Supraorbital ridges parallel or slightly divergent posteriorly, slender and dorsally reflect- ed in some specimens but thicker and produced laterally in others; postorbital processes (when present) usually small but occasionally large (e.g., ROM 96090); temporal ridges usually converging posteriorly. Palatine fenestrae present, but often consisting of many irregular holes on each side (rather than a single large, rounded opening); posterolateral palatal foramina small, usually similar in length to M4 (measured across paracone-metacone). Tympanic wing of alisphenoid laterally compressed, with ventral surface slightly pointed or bluntly keeled; medial process of ectotympanic indistinct or absent. I1 hypsodont, normally present in adults; crown of I2 sharply defined in relation to root; C1 without accessory cusps; preparacrista connected to stylar cusp B on M1– M3; stylar cusps D and E confluent, not separated by a distinct notch on M2.

COMPARISONS: Marmosa mexicana merits close comparisons with three other species of Marmosa (Marmosa) that have overlapping geographic ranges in Central America, namely M. zeledoni , M. isthmica , and M. robinsoni . Specimens of these four taxa are often misidentified in museum collections, but each can be distinguished by a combination of morphometric and qualitative traits. For completeness, we also provide pairwise comparisons with allopatric congeners ( M. xerophila , M. simonsi , M. rubra ) that, although unlikely to be confused with M. mexicana geographically, may prove to be closely related.

Adult specimens of Marmosa mexicana average smaller than adult M. zeledoni in most external and craniodental measure- ments (tables 4–7), but there is broad overlap in all measurements, and none provides a satisfactory basis for identification. In qualitative features, M. mexicana is most readily distinguished from M. zeledoni by its brighter dorsal coloration (the dorsal pelage of M. zeledoni appears duller and darker in side-byside comparisons); by the paler coloration of its midrostral fur, which contrasts sharply with the darker coloration of its crown fur (midrostral and crown fur are nearly the same color, seldom contrasting sharply, in M. zeledoni ); by the posterior extension of its dark facial mask, which usually contacts the base of the ear (the mask of M. zeledoni seldom extends posteriorly to the ear base); by the more frequent presence of distinct postorbital processes (postorbital processes are usually absent or indistinct in M. zeledoni ); and by the presence of palatine fenestrae (absent in M. zeledoni ). Other differences include the coloration of the tips of the gray-based ventral hairs (yellowish or orangish in M. mexicana versus reddish or brownish in M. zeledoni ), the morphology of the medial carpal tubercles of mature adult males (long and unsegmented in M. mexicana versus long but divided by a shallow sulcus into proximal and distal parts in M. zeledoni ), caudal hair length (the central hair of each caudal-scale triplet is about two scales long in M. mexicana versus about one-and-a-half scales long in M. zeledoni ), the size of the posterolateral palatal foramina (usually about as long as M4 measured across the paraconemetacone in M. mexicana versus usually shorter than M 4 in M. zeledoni ). In dorsal view, skulls of M. mexicana also have more laterally projecting and more posteriorly divergent supraorbital ridges, and temporal ridges that converge more strongly posteriorly, than skulls of like-aged M. zeledoni .

Adult specimens of Marmosa mexicana are distinctly smaller than adult M. isthmica in all measured external and craniodental dimensions (tables 4–7). Although no single measurement is sufficient for diagnosing these species, some of the observed overlap in external dimensions may be methodological artifacts; mean values for hind feet and ears are large enough to suggest that the size of these appendages might often be useful for field identification. It is also noteworthy that morphometric overlap is minimal in several ontogenetically invariant molar dimensions (e.g., UMS; tables 6, 7). Among the qualitative external characters we studied, M. mexicana is most easily distinguished from M. isthmica by the posterior extension of its dark facial mask, which usually contacts the base of the ear (the dark facial mask of M. isthmica does not contact the ear base); by its more reddish- (versus orangish-) brown dorsal fur; by the more extensive distribution of gray-based ventral fur, which covers the sides of its chest, abdomen, and upper inguinal region, sometimes also extending to the sides of the neck and inner parts of the arms and legs (gray-based ventral fur is restricted to the sides of the abdomen in M. isthmica ); and by the long, unsegmented medial carpal tubercles of mature adult males (the medial carpal tubercles of like-aged M. isthmica are divided by a shallow sulcus into subequal proximal and distal parts). In qualitative cranial characters, M. mexicana is most easily distinguished from M. isthmica by the presence of palatine fenestrae (absent in M. isthmica ) and by the usual absence or small size of postorbital processes (postorbital processes are usually present and much larger in fully mature examples of M. isthmica ).

Adult specimens of Marmosa mexicana are similar in size to adult M. robinsoni , although they average somewhat smaller in most dimensions (tables 4–7). On average, M. mexicana has a relatively longer tail than M. robinsoni , a difference that is noteworthy despite broad overlap in computed ratios (possibly another methodological artifact). In qualitative external characters, M. mexicana is most easily distinguished from M. robinsoni by the posterior extension of its dark facial mask, which usually contacts the base of the ear (the dark facial mask of M. robinsoni does not contact the ear base); by its more reddish- (versus yellowish-) brown dorsal fur; by its more conspicuous and more extensively distributed gray-based ventral fur, which covers the sides of its chest, abdomen, and upper inguinal region, sometimes also extending to the sides of the neck and inner parts of the arms and legs (gray-based ventral fur is often less conspicuous and is usually restricted to the sides of the abdomen in M. robinsoni ); and by the long, unsegmented medial carpal tubercles of mature adult males (the medial carpal tubercles of like-aged M. robinsoni are usually divided by a shallow sulcus into a globular proximal segment and a comma-shaped distal segment). In qualitative cranial traits, M. mexicana is most easily distinguished from M. robinsoni by its longer rostral process of the premaxillae, smaller and more irregularly shaped palatine fenestrae, smaller posterolateral palatal foramina, less inflated auditory bullae, and by the absence of a notch between styD and styE (a distinct notch is usually present in M. robinsoni ). In addition, a low sagittal crest that is sometimes present on the skulls of old adult specimens of M. robinsoni is never seen in M. mexicana .

Marmosa mexicana differs from M. xerophila in all of the same traits that distinguish M. mexicana from M. robinsoni , except that the rostral process of the premaxillae (long in M. mexicana , short in M. robinsoni ) is entirely absent in M. xerophila .

Marmosa mexicana is longer-tailed and smaller-eared, on average, than M. simonsi , but the two species are otherwise similar in univariate comparisons of measured external and craniodental dimensions (tables 4–7). In qualitative external traits, these taxa are most easily distinguished by their dorsal fur color (reddish brown in M. mexicana , distinctly grayish in M. simonsi ), ventral fur color (a continuous median streak of self-colored fur is present in M. mexicana but absent in M. simonsi ), and tail coloration (all-dark in M. mexicana , one-third to one-half white in M. simonsi ). In qualitative cranial traits, they are most easily distinguished by the rostral process of the premaxillae (long in M. mexicana , short in M. simonsi ), postorbital processes (usually indistinct or small in M. mexicana , consistently well developed in M. simonsi ), and by the notch between stD and stE on unworn M2 (absent in M. mexicana , present in M. simonsi ).

Marmosa mexicana is substantially small- er, on average, than M. rubra in most measured dimensions (tables 4–7), but only measurements of the upper molar series are diagnostic in same-sex univariate comparisons (UMS, tables 6, 7). In qualitative external traits, these species are most easily

TABLE 6 Summary Statistics a for Craniodental Measurements (mm) of Adult Male Specimens of Seven Species of Marmosa

TABLE 6 (Continued)

TABLE 7

Summary Statistics a for Craniodental Measurements (mm) of Adult Female Specimens of Seven Species of Marmosa

TABLE 7 (Continued)

TABLE 8 Morphological and Geographic Comparisons among Seven Species of Marmosa a

distinguished by rostral markings (a dark median stripe is absent in M. mexicana but present in M. rubra ), by the posterior extension of the dark facial mask (reaching the base of the ear in M. mexicana but not in M. rubra ), by the presence or absence of a gular gland (present in M. mexicana , absent in M. rubra ), by the arrangement of caudal scales (indeterminate in M. mexicana , distinctly spiral in M. rubra ), and by the length of caudal-scale hairs (the central hair of each triplet is about two scales long in M. mexicana , but only about one scale long in M. rubra ). In qualitative craniodental traits, these species are most readily distinguished by their palatal morphology (palatine fenestrae are present in M. mexicana but absent in M. rubra ), by the stylar terminus of the preparacrista on M1–M3 (at styB in M. mexicana , at styA in M. rubra ), and by the presence or absence of a distinct notch between styD and styE on M2 (absent in M. mexicana , present in M. rubra ).

GEOGRAPHIC DISTRIBUTION AND SYM- PATRY: Marmosa mexicana occurs in tropical and subtropical forests and shrubby habitats below 1600 m elevation from the Mexican states of Tamaulipas and San Luis Potosí southward to the eastern Panamanian province of Darién (fig. 17). It is also known from two offshore Caribbean islands, Isla de Roatán ( Honduras; locality 53) and Isla del Maíz Grande ( Nicaragua; locality 57).

In Mexico, this species occurs in both dry and moist forests that correspond to the Tropical Zone of Shelford (1926). However, Marmosa mexicana is also known from several localities (gazetteer entries 6, 10, and 11; appendix) where the Central American and Sierra Madre del Sur pine-oak forests are

TABLE 8 (Extended)

juxtaposed with Central American Pacific dry forests (as defined by Olson et al., 2001). In Central America, M. mexicana occurs in a wide variety of habitats that include dry and moist tropical forests, pine-oak forests, mangroves, and scrublands.

The range of M. mexicana overlaps that of M. zeledoni from northwestern Nicaragua to eastern Panama. The two species have been collected sympatrically at Río Coco (locality 60), Nicaragua; Finca Helechales (locality 79) and Monteverde (locality 80), Costa Rica; and Bugaba (locality 105), Panama. The range of M. mexicana also overlaps the known ranges of M. isthmica and M. robinsoni in Panama, although M. mexicana has apparently not been collected sympatrically with either of those species.

GEOGRAPHIC VARIATION: Available population samples of Marmosa mexicana exhibit variation in pelage color that is apparently related to habitat. Whereas specimens from pine-oak forests and moist forests tended to have rich reddish-brown dorsal fur and orangish ventral fur, specimens from dry forests and scrublands tend to be paler (with faded-reddish dorsal fur and yellowish buff or buff ventral fur). The palest specimens we examined were collected at Puerto El Triunfo ( El Salvador; locality 50) in the Northern Dry Pacific Coast Mangroves ecoregion of Olson et al. (2001). By contrast, we found no morphometric variation that could be unequivocally related to the geographic origin or habitat of the specimens analyzed.

TAXONOMIC HISTORY: The first literature reference to a specimen identifiable as Marmosa mexicana is in Waterhouse (1846), who identified a British Museum specimen from Mexico as Didelphys murina . Other 19thcentury authors also used murina for specimens of mexicana (e.g., Alston, 1880; Thomas, 1882b, 1888, 1895; Allen 1893) and, indeed, Merriam (1897) originally described mexicana as a subspecies of M. murina . Although Merriam provided only a brief description of mexicana , based primarily on the pelage of two specimens from the Mexican states of Oaxaca and Chiapas, most subsequent authors (except Allen, 1908, 1910; and Gaumer, 1917) seem to have agreed that mexicana was a distinct taxon. Bangs (1902) provided additional details about the pelage color and cranial morphology of mexicana , which he considered to represent a valid species. However, his conclusion was not immediately accepted by other mammalogists (e.g., Elliot, 1904, 1905).

Osgood (1913) described Marmosa mayensis based on a single specimen that he considered to represent the Yucatecan representative of M. mexicana . Later, Goldman (1917) described Marmosa mexicana savannarum based on five specimens from the Panamanian province of Chiriqui. In the same report, Goldman stated that ‘‘the continental Middle American forms now known [except for Marmosa canescens (5 Tlacuatzin canescens )] may confidently be referred to a single species,’’ thereby establishing a broad concept of M. mexicana that included not only mayensis and savannarum, but also isthmica and zeledoni .

Goldman’s (1917) conclusions were adopt- ed by Cabrera (1919), who listed isthmica , mayensis , savannarum, and zeledoni as subspecies of Marmosa mexicana in his influential checklist of marsupials. Tate (1933), however, recognized only M. mexicana mayensis and M. m. zeledoni as valid subspecies, treating savannarum as synonym of zeledoni , and recognizing M. isthmica as a valid species. In Tate’s classification, M. mexicana was referred to the monotypic Mexicana Section of the genus, whereas M. isthmica was referred to the Mitis Section. Tate’s (1933) opinions about the validity of subspecific taxa in his Mexicana Section were accepted by Hershkovitz (1951), Hall (1981), and most subsequent authors.

REMARKS: Osgood (1913) described mayensis as paler than mexicana , and Tate (1933) used this character to maintain these taxa as valid subspecies. However, our examination of the holotypes of mayensis (FMNH 19994) and mexicana (USNM 71526) revealed no conspicuous differences in pelage color that could serve as an unambiguous basis for taxonomic diagnosis. Although the holotype skull of mayensis is damaged (with only the rostral, palatal, and interorbital regions intact), the absence of any noteworthy qualitative or morphometric differences with the holotype skull of mexicana also support our opinion that mayensis and mexicana are conspecific.

Goldman (1917) described savannarum as smaller and paler than other Panamanian mouse opossums that he identified as ‘‘ M. mexicana zeledoni ’’ (5 M. zeledoni) and ‘‘ M. m. isthmica ’’ (5 M. isthmica). In fact, the differences in size and pelage color that he observed are marked, and they can be partially attributed to the specific status of the specimens he examined ( M. zeledoni and M. isthmica are, indeed, larger and darker than M. mexicana ). However, the holotype of savannarum (AMNH 18915) is a subadult with an incompletely erupted M4 (as noted by Tate, 1933), so its dimensions are not those of a fully mature individual. Our examination of the holotypes of savannarum and mexicana revealed no conspicuous differences other than the overall darker fur and broader gray-based lateral zones of ventral fur in the former specimen. Neither of these pelage differences exceeds the range of variation among other specimens that we refer to M. mexicana , however, and in the absence of qualitative osteological differences, we conclude that Goldman’s and Merriam’s taxa are conspecific.

Marmosa ruatanica was described by Goldman (1911) based on a single specimen (USNM 7785/37700 [skin/skull cataloged separately]) from Isla de Roatán, Honduras (locality 53). Tate (1933) also recognized ruatanica as a distinct species that included isthmica and mimetra as valid subspecies; these three nominal taxa were associated by virtue of their large size, well-developed postorbital processes, proportionately small alisphenoid tympanic processes, and minute or absent palatine fenestrae. By contrast, Hershkovitz (1951) considered ruatanica to be a subspecies of M. mitis , and ruatanica is currently regarded as a valid subspecies of M. robinsoni (e.g., by Hall, 1981; Gardner, 2005).

The large size of the holotype skull (fig. 18) is the principal characteristic that impelled several authors to compare ruatanica with the Trinidadian nominal taxon chapmani (5 M. robinsoni) or to associate it with M. isthmica (including mimetra ). However, the type of ruatanica closely resembles M. mexicana in several qualitative traits, including the posterior extension of its dark facial mask (which contacts the base of the ear), by its medial carpal tubercle (which is long and unsegmented), and by the modest development of its temporal ridges (which tend to be much more strongly developed in other species). In fact, craniodental measurements of the holotype, an old adult male, are not much larger than other like-aged specimens of M. mexicana , some of which exhibit comparably developed postorbital processes and have small irregular holes in place of better-defined palatine fenestrae. Although additional material from Roatan Island (from which only the type is currently known) would be welcome, we are not convinced either that ruatanica is a distinct taxon or that its relationships are with geographically distant forms of mouse opossums. Instead, we provisionally regard it as an insular form of the adjacent mainland species.

SPECIMENS EXAMINED (N 5 131): Without locality data (FMNH 34898, FMNH 49927; ROM 99608). MEXICO — Campeche, 44 km S Constitución (ROM 95795), Xpujil (ROM 96090). Chiapas, Chicharras (USNM 77680), Huehuetan (USNM 77681, 77682), Rayón (MVZ 159445, 159446), San José (MVZ 113483), Volcán Tacaná (MVZ 155505, 155506). Oaxaca, Juchitán (AMNH 189209), Lachiguirí (AMNH 213754), San Gabriel Mixtepec (AMNH 189483–189485), Santa Catarina Juquila (5 Juquila: USNM 71526 [holotype of Marmosa murina mexicana Merriam, 1897 ]), Tehuantepec (MVZ 149102–149107). San Luis Potosí, El Salto Falls (USNM 329396). Tamaulipas, Aserradero del Infernillo (AMNH 166059). Veracruz, Achotal de Moreno (FMNH 13805, 13806), Jalapa Enríquez (BMNH 97.9.9.82, 97.9.9.83;AMNH12453–12456/10762–10765), Mirador (USNM 62217–62219, 583340, A22019 ), Paso Nuevo (AMNH 17135, 17136), San Andrés Tuxtla (BMNH 7.1.1.186), Tuxpan de Rodríguez Cano (5 Tuxpan: USNM 10719). Yucatán, Chichén Itzá (AMNH 91192), Izamal (FMNH 19994 [holotype of Marmosa mayensis Osgood, 1913 ]). BE- LIZE— Cayo, Central Farm (BMNH 64.2028, 64.2029, 65.3870; FMNH 106525; USNM 360468, 360469), Georgeville (BMNH 65.3866–69, 65.3873–65.3879, 66.2329–66. 2332), Roaring Creek (BMNH 63.626, 65.3871). Orange Walk, Yo Creek (BMNH 65.3872). Stann Creek, Bokowina Hill (5 Bokowina: BMNH 84.369; FMNH 63887, 63888), Cockscomb Basin Wildlife Sanctuary (USNM 583001), Silk Grass (FMNH 63891). Toledo, Double Fall (BMNH 84.370), Union Camp (USNM 583214, 583215). GUATE- MALA —no other locality data (AMNH 14248). Alta Verapaz, Cobán (BMNH 75.2.27.15; FMNH 42040–42042), La Primavera (AMNH 79250). Baja Verapaz, Chilascó (AMNH 14377), San Jerónimo (BMNH 65.5.18.67). Chiquimula, Esquipulas (USNM 564594). Esquintla, San Jose (USNM 275673). Guatemala, Lago de Amatitlán (USNM 275672). Izabal, Bobos (FMNH 41578, 41677), Escobas (FMNH 41577), La Esmeralda (USNM 564588), Río Frío (USNM 564589). Progreso, 5 km E San Cristóbal Acasaguastlán (ROM 99776), Puerta de Golpe (USNM 564591). San Marcos, Nuevo Progreso (USNM 564592, 564593). Zacapa, Cabañas (AMNH 265851), Río Hondo (5 Finca El Chahuite: USNM 564590). EL SALVA- DOR— San Miguel, Laguna Olomega (MVZ 98165). Sonsonate, Chilata (5 Hacienda Chilata: MVZ 98164,130251), Sonsonate (AMNH 243700). Usulatán, Puerto El Triunfo (MVZ 130252, 130253). HONDURAS —Department unknown (received in banana shipment: FMNH 43309). Cortés, Catacombas (AMNH 123290). Francisco Morazán, Monte Vásquez (5 Cerro Vásquez: USNM 257078). Islas de la Bahía, Isla de Roatán (5 Ruatán Island: USNM 7785/37700 [holotype of Marmosa ruatanica Goldman, 1911 ]). La Paz, Humuya (AMNH 126588–126590). NICARAGUA — Atlántico Sur, Isla del Maíz Grande (5 Great Corn Island: FMNH 34072, 34073). Chinandega, Volcán San Cristóbal (5 Volcán de Chinandega: AMNH 28314). Jinotega, Río Coco (AMNH 29270). Managua, Managua (USNM 337503). Matagalpa, Matagalpa (AMNH 29269). Nueva Segovia, Ocotal (AMNH 28506). Rivas, San Emilio (BMNH 97.4.7.12). Santa Barbara , San Jose de Santa Barbara (AMNH 123291). COSTA RICA — Puntarenas, Finca Helechales (USNM 547996, 548001, 548002), Monteverde (FMNH 126076). PANAMA — Chiriquí, Bugaba (5 Bogava: BMNH 0.7.11.90; USNM 248344), Boquerón (AMNH 18914, 18915 [holotype of Marmosa mexicana savannarum Goldman, 1917 ]). Darién, Yaviza (MVZ 135833).

OTHER SPECIMENS: In addition to material positively identifiable as Marmosa mexicana , we examined five specimens that we provisionally refer to this species. Three are very young specimens preserved in fluid ( USNM 297454–297456 ; from Diriamba [locality 58], Nicaragua), and two are skins unaccompanied by skulls (BM 94.11.1.7,

94.11.1.8; from Volcán San Cristóbal [locality 59], Nicaragua). Although the latter specimens exhibit some mexicana –like external traits (e.g., a dark circumocular mask extending to the base of the ear; long and unsegmented medial carpal tubercle), they seem to have shorter tails and yellower fur than is usual in the species.