Oecomys roberti (Thomas)

Identification. Specimens from the mid-Araguaia (Fig. 9 b) conform to the description of craniodental characters of specimens from the Juruá River basin (Patton et al. 2000). The skull is characterized by relatively short rostrum, shallow zygomatic notches and interorbital region converging anteriorly with supraorbital ledges. The incisive foramen is teardrop-shaped and reaches the anterior end of molar rows. The mesopterygoid fossa is slightly arched, sphenopalatine vacuities are absent and mesopterygoid roof is totally ossified. Posterior palatal pits are large and divided. It also has the pattern 1 of carotid circulation (sensu Voss 1988). The alisphenoid strut is absent in the two specimens analyzed. The hamular process of squamosal is short and broad, and in one specimen occludes the subsquamosal foramen. Upper incisors are opisthodont and labial accessory root of M1 is present.

Measurements (n = 1): HB = 100, T = 135, HF = 26, E = 19, W = 39.

Distribution. This species occurs in Amazonian region in western Brazil (Musser & Carleton 2005).

Natural history. One adult male and one juvenile female were collected in Sherman traps placed on the ground on the west bank of the mid-Araguaia River at FSF, state of Pará.

Vouchers (n = 2: 1ɗ 1Ψ): UFES 1369–1370.