Proechimys decumanus
Creators: name: Don E. Wilson
name: Thomas E. Lacher, Jr
name: Russell A. Mittermeier
Publisher: name: Lynx Edicions
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Echimyidae
Proechimys
Proechimys decumanus

description: 33.
Pacific Spiny-rat
Proechimys decumanus
French: Rat-épineux cotier / German: Pazifik-Kurzstachelratte / Spanish: Rata espinosa del Pacifico
Taxonomy. Echimys decumanus Thomas, 1899,
“Chongon, Guayas Province, west of Guayaquil, Ecuador.” Restricted by R. A. Paynter, Jr. in 1993 to “ca. 100 m, 25 km west of Guayaquil.”
This species is monotypic.
Distribution. Pacific coastal lowlands of Ecuador and NW Peru.
Descriptive notes. Head-body 260-300 mm, tail 196 mm. No specific data are available for body weight. The Pacific Spiny-ratis large-bodied, with proportionately shorttail (¢.65% of head—body length). Dorsal color is coarsely grizzled sandy fawn; sides are paler and grayer; face is grizzled gray; and venter and inner sides of forearms and hips are pure white, with hairs white to bases. Upper surfaces of forefeet and hindfeet are white, or slightly washed yellow, and white on inner thighs is continuous across ankle to foot. Plantar pads of hindfeet are large, particularly thenar and hypothenar pads. Tail is bicolored, dark above and pale below, and uniformly but thinly haired with scale annuli narrow (averaging 13 annuli/cm) and visible to the eye. Aristiform spines are long (length 25-27 mm), thin (width 0-5 mm), and tipped with long flexible filament. As a result, pelage is inconspicuously spiny to the eye and touch. Skull of the Pacific Spiny-rat is large and elongated, but rostrum is short and broad. Temporal ridges are moderately developed and either continuous or interrupted across parietals from posterior end of supraorbital flange. Incisive foramina are oval to slightly lyrate in shape and large, with weakly developed posterolateral flanges and weak grooves extending onto anterior palate; premaxillary part of septum is long, but tapers posteriorly and is in direct contact with maxillary part, which is varyingly developed as either thin, spiculate bone or broad shelf, often perforated by small foramen, and with either no or only limited keel that extends onto anterior palate; and vomer is not visible along septum. Floor of infraorbital foramen is flat, rarely with limited evidence of lateral flange indicating passage of infraorbital branch of maxillary nerve. Mesopterygoid fossa is moderately deep, reaching to anterior one-half of M?, and rather narrow, with its angle averaging 53°. Post-orbital process of zygoma is obsolete. Cheekteeth are simple, typically with three counterfolds on all upper teeth (although rarely only two on M?), and with three folds on dP, and M, but only two folds on M, and M,. Counterfold formula is thus 3-3-3-(2)3 / 3-3-2-2. Baculum is long but stout, among the longest of any species of Proechimys, with average length of 10-12 mm and maximal width 2-8-3-8 mm. In size and shape, baculum of the Pacific Spiny-rat is most similar to those of members of the trinitatisspecies group, with almost parallel sides, rounded base, and only slightly expanded distal tip with weak median depression. Chromosomal complement is 2n = 30 and FN = 54.
Habitat. Dry lowland, semideciduous rainforest along the coast and lower foothills of western slope of the Andes from sea level to elevations of ¢.800 m.
Food and Feeding. There is no specific information available for this species, but the Pacific Spiny-rat, as other species of Proechimys, likely feeds on seeds, fruits, and other plant parts.
Breeding. There is no information available for this species.
Activity patterns. There is no specific information available for this species, but the Pacific Spiny-rat is assumed to be nocturnal and terrestrial.
Movements, Home range and Social organization. There is no specific information available for this species, but the Pacific Spiny-rat is presumed to be a solitary.
Status and Conservation. Classified as Vulnerable on The IUCN Red List. This ranking is somewhat puzzling because the Pacific Spiny-rat has very limited distribution, and its semideciduous forest habitat is being heavily altered by human activity. Additional studies on distribution, habitat, abundance, ecology, and conservation threats to the Pacific Spiny-rat are needed.
Bibliography. Allen (1899a), Eisenberg & Redford (1999), Emmons (1990, 1997a), Moojen (1948), Patton (1987), Patton & Gardner (1972), Patton & Leite (2015), Patton & Reig (1989), Paynter (1993), Thomas (1899b), Woods & Kilpatrick (2005).
description: Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Echimyidae, pp. 552-604 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 570, DOI: 10.5281/zenodo.6623649