Oecomys galvez, Voss & Fleck & Jansa, 2019

Voss, Robert S., Fleck, David W. & Jansa, Sharon A., 2019, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 5. Rodents, Bulletin of the American Museum of Natural History 2024 (466), pp. 1-180 : 75-78

Oecomys galvez , new species

Figures 30A, 30D, 31A, 32A

Oecomys trinitatis : Patton et al., 2000: 131 (a misidentification; not Oryzomys trinitatis Allen and Chapman, 1893 ).

HOLOTYPE: The holotype, MUSM 13320, consists of the skull, fluid-preserved body, and frozen tissues of an adult male collected by Robert S. Voss (original number RSV 2023) at Nuevo San Juan on 20 May 1998. The frozen tissues of the holotype are preserved in the Ambrose Monell Cryo Collection at the American Museum of Natural History with catalog number M-280496.

OTHER VOUCHER MATERIAL (N = 10): Jenaro Herrera ( AMNH 276720; MUSM 16002, 23819), Nuevo San Juan ( AMNH 273033, 273088, 273122; MUSM 15336–15339).

OTHER SPECIMENS EXAMINED (N = 15): Brazil — Acre, opposite Igarapé Porongaba on left bank of Rio Juruá (MVZ 200948); Amazonas, Barro Vermelho on left bank of Rio Juruá (MVZ 200949), Colocação Vira-Volta on left bank of Rio Juruá (MVZ 200953, 200954), Penedo on right bank of Rio Juruá (MVZ 200955). Ecuador — Orellana, 38 km S Pompeya Sur (ROM 105224, 118789, 118850), 42 km S Pompeya Sur (ROM 106145, 118868), 66 km S Pompeya Sur (ROM 105985, 105986), 76 km S Pompeya Sur (ROM 105321, 106068). Peru — Loreto, San Jacinto (KU 158192).

DESCRIPTION: Oecomys galvez is a large (41– 75 g) species with 7–10 mm long, tawnybrownish dorsal fur and grayish-white ventral fur (the individual hairs have long gray bases and whitish tips). The transition from dorsal to ventral coloration is abrupt, without any intervening ochraceous line along the flanks. The medial metatarsus and the digits of the hind foot are covered dorsally with short, pale hairs, but the lateral metatarsus is usually covered with darker hairs. The ungual tufts are short and sparse, not concealing the claws on any of the pedal digits (fig. 31A). The tail is long (about 126% of head-and-body length, on average), unicolored (dark above and below), and lacks a terminal pencil (the apical hairs are ≤ 3 mm long); we counted 17–20 caudal scale rows/ cm on several fluid-preserved specimens. The preputial glands are large, extending anteriorly beyond the ventral flexure of the penis.

In dorsal cranial view (fig. 30A) the rostrum is flanked by moderately deep zygomatic notches, and postorbital processes are absent; the temporal crests (marking the dorsal origin of the temporalis muscle) are only weakly developed on the parietal bones. In ventral cranial view (fig. 30B), the incisive foramina are diagnostically short (LIF/LD = 0.56 ± 0.04) and terminate well anterior to the alveoli of the first maxillary molars; in most specimens these foramina are widest posteriorly (behind the premaxillary-maxillary suture) and taper anteriorly. Sphenopalatine vacuities (paired openings in the bony roof of the mesopterygoid fossa) are consistently absent. Alisphenoid struts (separating the buccinator-masticatory and accessory oval foramina) are variable in this species: they are bilaterally present in eight specimens, bilaterally absent in another eight, and unilaterally present in two. The stapedial arterial circulation is complete, with a well-developed supraorbital branch (pattern 1 of Voss, 1988). The subsquamosal fenestrae are small but patent (exposing the interior braincase) in fewer than half the specimens we examined; in most specimens these fenestrae are either occluded internally by a bony flange of the petrosal, or they are absent altogether. The mastoid capsules are consistently unfenestrated.

The molar dentition seems to lack any distinctive features.

Karyotyped specimens of Oecomys galvez (originally identified as O. trinitatis ; see below) include one from Jenaro Herrera reported by Sokolov and Malygin (1994) and four reported by Patton et al. (2000) from western Brazil; all had 2 n = 58 chromosomes. We have not seen the specimen from Jenaro Herrera (ZMMU S-151008), but it was examined by the late G.G. Musser, whose unpublished notes (in the AMNH Mammalogy archives) mentioned that it closely resembled Patton et al.’s Brazilian material.

VARIATION: Sequenced specimens that we refer to Oecomys galvez belong to two strongly supported mtDNA clades from opposite sides of the Amazon (fig. 33). However, representative specimens of these northern and southern haplogroups are morphometrically indistinguishable (table 23), and we were unable to find any consistent qualitative differences between these populations by visual comparisons of skins and skulls.

COMPARISONS: Specimens of Oecomys galvez from western Brazil were previously identified as O. trinitatis (Allen and Chapman, 1893) by the late G.G. Musser, whose recommended taxonomy of Brazilian Oecomys was adopted by Patton et al. (2000). Although no justification for this identification was provided, O. galvez and O. trinitatis both have gray-based ventral pelage, tails that lack a distinct pencil of long apical hairs, and deeper zygomatic notches than those of many other congeneric species. Additionally, O. galvez and O. trinitatis (sensu stricto) 23 are about the same size and overlap in all measured external and craniodental traits. Nevertheless, O. trinitatis differs from O. galvez in several morphological and chromosomal traits (table 24). Among other contrasts, O. trinitatis has longer dorsal fur, denser and longer ungual tufts on digits II–V of the hind foot (fig. 31B), and incisive

23 Carleton and Musser (2015: 417) acknowledged that their concept of Oecomys trinitatis was probably composite, and we agree. Therefore, we restricted our comparative sample to the following adult specimens from Trinidad (the type locality) and the adjacent continental mainland: Trinidad and Tobago — Trinidad, Bush Bush Forest ( AMNH 185472 , 186732 , 186736 , 188414 ), Caura ( AMNH 7728 /6113, BMNH 99.9.4.5), Maingot Estate ( AMNH 174067 ), Princestown ( AMNH 5943 /4673 [holotype]). Venezuela — Monagas, 3–5 km NW Caripe ( USNM 409875 , 409876 , 409878 , 409879 ) ; Sucre, Campo Alegre ( BMNH 0.5.1.11, 0.5.1.12, 0.5.1.18), La Hormiga ( BMNH 0.5.1.13, 0.5.1.14), Latal ( AMNH 69862 , 69866–69868 ), Los Palmales ( BMNH 2.3.6.52), Neverí ( AMNH 69858 , 69859 ), Quebrada Seca ( BMNH 0.5.1.15; AMNH 14729, 14733, 14735), Spure ( BMNH 0.5.1.16, 0.5.1.17) .