Proechimys longicaudatus (Rengger, 1830)

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Echimyidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 552-604 : 579

52.

Long-tailed Spiny-rat

Proechimys longicaudatus

French: Rat-épineux longicaude / German: Langschwanz-Kurzstachelratte / Spanish: Rata espinosa de cola larga

Taxonomy. Echimys longicaudatus Rengger, 1830 ,

“Northern Paraguay.” Restricted by O. Thomas in 1903 to “the 21* parallel of latitude, therefore not far south of Corumba,” Mato Grosso do Sul State, Brazil.

Proechimys longicaudatus is a member of the longicaudatus-species group. It includes myosurus, myosrurus, lewcomystax, villacauda, and ribeiroi as synonyms. Monotypic.

Distribution. SC Brazil, E Bolivia, and N Paraguay.

Descriptive notes. Head-body 220-250 mm, tail 131-150 mm. No specific data are available for body weight. The Long-tailed Spiny-rat is medium-sized, similar to other members of the longicaudatusspecies group in its proportionally short tail (60-63% of head-body length), but differs in its distinctly pale reddish or yellowish brown pelage, streaked with dark brown, that contrasts sharply with dark reddish brown mixed with black appearance of the Short-tailed Spiny-rat ( P. brevicauda ) and Cuvier’s Spinyrat (P. cuvierr). Venter is pure white, without hint of buffy overtones. Dorsal surfaces of hindfeet can be highly variable, from uniformly white, including toes (most specimens), to mostly dusky, or dusky laterally and white medially. Dark ankle band may or may not separate white inner thigh from white foot. Tail is bicolored and thinly haired, with obvious scales and scale annuli averaging 9-10/cm at mid-length. Fur is relatively soft to the touch, with aristiforms narrow (0-6—0-7 mm), rather short (17-18 mm), and terminating with long whip-like tips. Cranially, the Long-tailed Spiny-rat is similar in nearly all features to other members of this species complex, butits skull is generally smaller than that of the Short-tailed Spiny-rat or Cuvier’s Spiny-rat. Temporal ridge varies from weakly continuous across parietals or is limited to simple posterior extension of supraorbital ledge. Lyrate shape of incisive foramina are as in the Short-tailed Spiny-rat and Cuvier’s Spiny-rat, with typically well-developed posterolateral flanges that extend onto anterior palate forming deep groves, and expanded and long premaxillary part of septum with short, often thin, but typically keeled maxillary part that continues as median ridge onto anterior palate; and vomer part of septum is short but exposed. Floor of infraorbital foramen is smooth, without groove for infraorbital nerve. Post-orbital process of zygoma is well developed, with equal contributions of Jugal and squamosal. Mesopterygoid fossa is broad (angle averages 78°) but penetrates posterior palate to middle of M®. All maxillary cheekteeth have three counterfolds; mandibular cheekteeth vary from three (rarely four) on P, to 2-3 folds on each lower molar. Counterfold formula is 3-3-3-3/3(4)-2(3)-2(3)-2(3). Population samples of Long-tailed Spiny-rats have a higher percentage of individuals with two folds on lower molars than those of other species in the group. This pattern fits a general trend of decreasing counterfold number across species, or their populations, along environmental gradient from extremely wet forests (trans-Amazonian Choco and western Amazon) to dry forests (eastern Amazonia and central Brazil). Other examples ofthis trend are the Napo Spiny-rat ( P. quadruplicatus ) in the western Amazon vs. Goeldi’s Spiny-rat (FP. goeldii ) in the east, or specimens of Tomes’s Spiny-rat ( P. semispinosus ) from the Choco in western Colombia vs. those in southern Ecuador (isolated subspecies rosa). Baculum of the Long-tailed Spiny-rat is robust, long (length 1-1-1 mm), and wide (proximal width 0-3-0-5 mm; distal width 0-51-0-52 mm), with short, stout apical wings. In these general features,it is virtually identical to the Short-tailed Spiny-rat. Chromosomal complement is 2n = 28 and FN = 48-50.

Habitat. Dry tropical rainforest and mid-savanna and grassland habitat near shaded areas at elevations of 50-1000 m. The Long-tailed Spiny-rat is present in primary and secondary habitats and has been reported to den in termite mounds and armadillo burrows.

Food and Feeding. There is no specific information about this species, but the Longtailed Spiny-rat is presumably eats fruits, seeds, and other plant parts.

Breeding. In longitudinal trapping studies in eastern Bolivia, reproduction of the Long-tailed Spiny-rat appears to commence in early September after a hiatus, based on first appearance of lactating and late-gestation females and shortly before young began to appear in traps. Pregnancies, however, have been recorded in Bolivian specimens in March and August.

Activity patterns. There is no specific information about this species, but the Longtailed Spiny-rat is generally regarded as terrestrial and nocturnal.

Movements, Home range and Social organization. There is no information available for this species.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Longtailed Spiny-rat is widespread, but its primary dry tropical forest habitat has been severely declining in recent decades due to agricultural expansion in Bolivia, Brazil, and Paraguay; also in Brazil pipelines bisect remaining habitat patches. Critical evaluation of current, range-wide population numbers and connectivity are required to properly determine current conservation status of the Long-tailed Spiny-rat.

Bibliography. Anderson (1997), Eisenberg & Redford (1999), Emmons (1990, 1997a, 2009), Geoffroy Saint-Hilaire (1840), Lichtenstein (1830), Miranda-Ribeiro (1914), Moojen (1948), Patton (1987), Patton & Gardner (1972), Patton & Leite (2015), Patton & Reig (1989), Pictet (1841), Rengger (1830), Thomas (1901a, 1903b), Wagner (1843), Woods & Kilpatrick (2005).

Figures

12. Broad-headed Spiny-rat (Clyomys laticeps), 13. Guiara (Euryzygomatomys spinosus), 14. White-spined Spiny-rat (Irinomys albispinus), 15. Elias’s Spiny-rat (Trinomys eliasi), 16. Rigid-spined Atlantic Spiny-rat (Trinomys paratus), 17. Yonenaga’s Spiny-rat (Trinomys yonenagae), 18. Elegant-spined Atlantic Spiny-rat (Trinomys setosus), 19. Moojen’s Spiny-rat (Trinomys moojeni), 20. Pau Brasil Spiny-rat (Trinomys mirapitanga), 21. Rio de Janeiro Spiny-rat (Trinomys dimidiatus), 22. Sao Paulo Spiny-rat (Trinomys thering), 23. Gracile Atlantic Spiny-rat (Trinomys gratiosus), 24. Sao Lourenco Punare (Thrichomys laurentius), 25. Jacobina Punare (Thrichomys inermis), 26. Lagoa Santa Punare (Thrichomys apereoides), 27. Pantanal Punare (Thrichomys pachyurus), 28. Foster’s Punare (Thrichomys fosteri), 29. Painted Tree-rat (Callistomys pictus), 30. Coypu (Myocastor coypus), 31. Armored Rat (Hoplomys gymnurus)

Distribution. SC Brazil, E Bolivia, and N Paraguay.