Proechimys brevicauda (Günther, 1876)

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 : 136

Proechimys brevicauda (Günther, 1876)

Figures 56A, 56D

VOUCHER MATERIAL (N = 27): Nuevo San Juan (AMNH 268273, 268275, 268276, 268281, 268282, 272698, 272700; MUSM 11258, 11262, 11297, 11298, 11316, 13337, 13338), San Fernando (FMNH 88959), San Pedro (MVZ 198475; UF 30548–30550, 30552–30555, 30603, 30637, 30713), Siete de Julio (UF 30775). Pacheco (1991) and Pavlinov (1994) also recorded this species from Jenaro Herrera based on collected material (at the ZMMU and MUSM, respectively) that we have not seen.

UNVOUCHERED OBSERVATIONS: Field identifications of this species cannot be accepted as valid without supporting voucher material.

IDENTIFICATION: Proechimys brevicauda is a medium-sized species that, in our region, has dark-brownish dorsal fur and ventral fur that is often mottled with buff or pale-brown markings; one specimen (UF 30549), however, has almost entirely pale-brown ventral fur, with whitish blotches only on the chest and inguinal region. Brownish ventral markings are especially seen on the throat, which is not pure white in any specimen we examined. Even in specimens with mostly whitish ventral fur, the color transition to the dorsal fur tends to be less abrupt than in most other species (e.g., P. kulinae , P. simonsi , P. steerei ) because there is often a lateral line of buff or pale-brown fur. The ventral fur is thin and feels harsh to the touch because it consists mostly of soft spines with only a few wool hairs mixed among them. The hind feet appear darker than in most other sympatric species because the pedal fur is brownish (pale brown in some specimens, but never pure white). The baculum (which we examined from five specimens) is about 9.6 mm long and about 4.0 mm wide proximally, on average, with short but well-developed apical processes and an average width-to-length ratio of 0.47 (range = 0.40–0.49).

Distinctive craniodental features of this species include consistently lyrate (but sometimes only weakly lyrate) incisive foramina from which more or less distinct lateral grooves extend posteriorly onto the anterior palate, which also exhibits a median ridge. The incisive septum is always complete in the specimens we examined, with a long premaxillary portion and a maxillary process that is often strongly keeled. The vomer is broadly exposed in most specimens. The mesopterygoid fossa usually penetrates between the third molars, but not as deeply as in other species (mean score for this character = 2.1, range = 1–3). The floor of the infraorbital foramen is almost always smooth, the temporal crest lacks a distinct parietal extension, and there are only three labial folds on all the upper cheekteeth (3-3-3-3) in the specimens we examined.

The phenotype we identify as Proechimys brevicauda closely resembles Patton and Leite’s (2015: 971–972) description with the noteworthy exceptions that (1) none of our specimens could really be described as reddish brown, (2) the mesopterygoid fossa penetrates between the third molars in most of our specimens, and (3) none of our specimens has a well-developed parietal extension of the temporal crest. Despite such discrepancies—and a few others involving morphological traits we did not score for analysis—phylogenetic analyses of DNA sequence data obtained from three specimens collected in our region ( AMNH 272698 , 272700 ; MUSM 13338) recovered them as members of the same molecular clade previously associated with this name ( Dalapicolla et al., 2024: appendix E, fig. S4). Measurements of our material (table 40) broadly overlap those of Patton et al.’s (2000: table 64) series from the Rio Juruá .