Oecomys

Rocha, Rita G., Ferreira, Eduardo, Costa, Barbara M. A., Martins, Iracy C. M., Leite, Yuri L. R., Costa, Leonora P. & Fonseca, Carlos, 2011, Small mammals of the mid-Araguaia River in central Brazil, with the description of a new species of climbing rat, Zootaxa 2789, pp. 1-34 : 19-20

Oecomys sp.

Identification. The series of Oecomys sp. specimens reported here present high morphological variation, and still very low genetic divergence ( Fig. 8 ). The very short and broad rostrum that characterizes the holotype of O. cleberi ( Locks 1981) was found only in one specimen (UFES 1353) ( Fig. 9 c) among 34. Zygomatic notches are shallow but not as much as in O. paricola and O. roberti . The interorbital region converges anteriorly and has well-developed supraorbital ledges extending onto the parietals. The incisive foramen is oval and reaches the anterior end of molar rows. The mesopterygoid fossa is slightly arched or squared at the anterior end. Sphenopalatine vacuities are either absent and mesopterygoid roof is totally ossified or present as narrow openings. Posterior palatal pits are present, usually divided and sometimes recessed in shallow depression. It has the pattern 1 of carotid circulation (sensu Voss 1988) in which the stapedial foramen and posterior opening of alisphenoid canal are large and the squamosal-alisphenoid groove and sphenofrontal foramen are present. The alisphenoid strut is either present or absent. The hamular process of the squamosal is short and broad, and in some specimens occludes the subsquamosal foramen. Upper incisors are opisthodont and labial accessory root of M1 is present.

Measurements (n = 19): HB = 90–125, T = 102–150, HF = 21–26, E = 13–19, W = 22–56.

Distribution. Oecomys sp. was collected on both banks of the mid-Araguaia River, states of Pará and Tocantins. Additional specimens collected at Santa Teresa River, 20 km NW Peixe, state of Tocantins, were also allocated to this species.

Natural history. Thirty-four specimens (19 adults and 15 juveniles) of Oecomys sp. were collected. These captures took place mainly in alluvial forest at PEC. They were also trapped in upland forests on the west bank of the Araguaia River at FSF, and in ipucas and Cerrado sensu strictu at FLV. Fourteen adult males had scrotal testes; in October 2006 one adult female was collected with four embryos.

Vouchers (n = 34: 17ɗ 17Ψ): UFES 1339–1364, 1430 –1437.

Figures

FIGURE 8. Bayesian tree of cyt-b haplotypes from specimens of Oecomys rooted using Hylaeamys and Thomasomys. Bayesian posterior probabilities are in bold and percentages are average Kimura two-parameter distances.

FIGURE 9. Dorsal, ventral and lateral views of skull and mandible of: a) Oecomys paricola (female, UFES 1368), b) Oecomys roberti (female, UFES 1370) and c) Oecomys sp. (female, UFES 1353).