Proechimys steerei Goldman, 1911

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 : 145-146

Proechimys steerei Goldman, 1911

Figures 57C, 57F

VOUCHER MATERIAL (N = 5): Nuevo San Juan (AMNH 268279; MUSM 11278, 11279, 11281, 11282). Pacheco (1991) and Pavlinov (1994) also recorded this species from Jenaro Herrera based on material (at MUSM and ZMMU, respectively) that we have not seen.

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

IDENTIFICATION: The four adult specimens we identify as Proechimys steerei are large rats with rich reddish-brown dorsal pelage—close to Ridgway’s (1912) Amber Brown or Chestnut— and pure-white ventral fur that is noticeably denser and softer than the ventral fur of other sympatric congeners. The hind feet are mostly dark, but there is an indistinct streak of whitish hairs along the medial metatarsus that extends distally to the base of digit I. The tail is bicolored (dark above, paler below), but this marking is not as sharp as it is in other sympatric congeners (e.g., P. simonsi ). The baculum (which we examined from two specimens) seems remarkably small for such big rats (only 8.4–9.6 mm long and 2.2–2.7 mm wide basally) and it has indistinct apical processes.

The incisive foramina are long and weakly lyrate with a complete septum composed of a short premaxillary process and a very long, narrow, and strongly keeled maxillary process; the vomer is concealed in three of our four adult specimens. Distinct grooves extend posteriorly from the incisive foramina onto the anterior palate, where they are separated by a low median ridge. The mesopterygoid fossa does not extend between the toothrows in one specimen, penetrates only between the M3 hypocones in two others, and extends between the M3 protocones in the fourth. The floor of the infraorbital foramen is grooved by a rather weakly defined nerve canal, and the temporal crests usually extend only a short distance onto the parietals. Examined specimens have either 3-3-4-3 or 3-3-3-3 labial folds on the upper cheekteeth. In all these respects our material resembles the morphology of P. steerei as described by Patton and Leite (2015), and measurements of our series (table 41) fall within the range of variation reported by Patton et al. (2000: table 78) for their Rio Juruá material.

ETHNOBIOLOGY: The Matses have no special name for this species.

MATSES NATURAL HISTORY: No interviews were focused on this species.

REMARKS: Our four adult specimens were trapped on the ground in the floodplain of the Río Gálvez—one in seasonally flooded forest and three in primary forest on a levee island surrounded by seasonally flooded forest. One juvenile was trapped near the river, but in secondary upland forest.