Thylamys macrurus (Olfers, 1818)

Giarla, T. C., Voss, R. S. & Jansa, S. A., 2010, Species Limits And Phylogenetic Relationships In The Didelphid Marsupial Genus Thylamys Based On Mitochondrial Dna Sequences And Morphology, Bulletin of the American Museum of Natural History 2010 (346), pp. 1-67 : 38-39

Thylamys macrurus (Olfers, 1818)

SYNONYMS: griseus Desmarest, 1827; marmotus Oken, 1816 (unavailable).

DISTRIBUTION: Thylamys macrurus is only known from eastern Paraguay and the adjacent Brazilian state of Mato Grosso do Sul. Published range maps based on correctly identified material of this species are in Carmignotto and Monfort (2006: fig. 7), Creighton and Gardner (2008: map 50), and Voss et al. (2009: fig. 3). Additional Brazilian records that we assume to be valid were reported by Cáceres et al. (2007). As noted by Voss et al. (2009), a Bolivian record (in Anderson, 1997) and a record from NE Argentina (mapped by Brown, 2004) are based on misidentifications. Voss et al. (2009: 417–418) discussed the problematic ecological interpretation of capture records for this species, which has been taken in arborescent Cerrado habitats in Brazil but in second-growth moist forest in Paraguay. This species is not known to occur sympatrically with any other congener.

MORPHOLOGICAL DIAGNOSIS: Body pelage tricolored (abrupt line of transition from darker middorsal to paler lateral coloration present); ventral pelage self-white (or -whitish), usually with narrow lateral zones of gray-based fur; plantar pads of manus separate, surrounding concave central palmar surface, and with well-developed dermatoglyphs; manual claws short, not extending much if at all beyond fleshy apical pads of digits; tail much longer than combined length of head and body (LT/HBL X 100 5 123%; N 5 5), with pale tip (terminal 10–50 mm whitish above and below); ventral prehensile surface of tail tip well developed. Nasal bones long (extending posteriorly as far as lacrimals) or very long (extending posteriorly beyond lacrimals); lacrimal foramina partially exposed on orbital margin or concealed inside orbit; infraorbital foramen above P3 or above P3/M1 commissure; nasolabial fossa shallow; supraorbital margins usually bead- ed, the beads sometimes developed as postorbital processes in old adult males; maxillary fenestrae present; crown of second upper incisor (I2) smaller than or subequal to crown of I3; stylar cusp C almost always present on M1 and M2; metaconule distinct on M3 (but only one specimen confidently scored for this trait).

COMPARISONS: Thylamys macrurus has been described as the largest species in the genus ( Solari, 2003; Carmignotto and Monfort, 2006), but it exhibits broad morphometric overlap with some species in the Elegans and Venustus groups, from which it is more readily distinguished by qualitative external and craniodental characters (table 16). Within the nominotypical subgenus, macrurus is qualitatively similar to pusillus (both species usually have beaded supraorbital margins, maxillary fenestrae, stylar cusp C on M1 and M2, and a distinct metaconule on M3), but macrurus is much larger (e.g., with nonoverlapping molar measurements; table 16), usually has narrow lateral zones of gray-based ventral fur (the ventral pelage is entirely self-white in pusillus ), a pale tail tip (usually absent in pusillus ), and shorter posterolateral palatal foramina (see Carmignotto and Monfort, 2006: fig. 6).

REMARKS: The complex nomenclatural history of this species was reviewed by Voss et al. (2009), who designated a neotype and tabulated measurement data from most of the known adult and subadult specimens. A detailed morphological description based on freshly collected Brazilian material was provided by Carmignotto and Monfort (2006), who also tabulated measurement data and illustrated craniodental traits not depicted in this report.

SPECIMENS EXAMINED (N 5 11): Brazil — Mato Grosso do Sul, Campo Grande ( MZUSP 3782 ), Fazenda Califórnia ( MZUSP 32094 , 32095 , 32096 ), Fazenda Santa Terezinha ( MZUSP 32097 ). Paraguay — Amambay, 28 km SW Pedro Juan Caballero ( UMMZ 125243 [neotype], 125259, 125260) ; Central , Asunción ( BMNH 99.11.17.1) ; Concepción, 7 km NE Concepción ( MSB 70700) ; Paraguarí, Sapucay ( BMNH 3.4.7.21) .