Mesomys occultus Patton, da Silva & Malcolm 2000
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
Mesomys
Mesomys occultus

description: 63.
Hidden Spiny Tree-rat
Mesomys occultus
French: Rat-épineux furtif / German: Blischelschwanz-Amazonas-Stachelratte / Spanish: Rata arboricola oculta
Other common names: Tufted-tailed Spiny Tree-rat
Taxonomy. Mesomys occultus Patton, da Silva & Malcolm, 2000,
“Colocacao ViraVolta, left bank Rio Jurud on Igarapé Arabidi, affluent of Parana Breu, Amazonas, Brazil (3°17’S, 66°14°'W).”
This species is monotypic.
Distribution. W Amazon Basin of W Brazil, S of the Amazon River, in the lower Jurua and Urucu rivers in Amazonas State.
Descriptive notes. Head-body 167 mm, tail 183 mm. No specific data are available for body weight. The Hidden Spiny Tree-rat is sympatric with Ferreira’s Spiny Tree-rat (M. lispidus) at both known localities, sharing substantial morphological similarity but sharply different karyotypes and deeply divergent mtDNA genomes. It is equivalent to Ferreira’s Spiny Tree-rat in size, color, color pattern, and degree of spine development in dorsal fur, but it differs by its spines on neck and shoulders, with orange mid-bands. Hairs along tail are thin and colorless, and tuft of hairs at tail tip are longer, averaging greater than 30 mm. At base oftail, central pigmented hair of each scale is elongated rather than spine line. Cranially, the Hidden Spiny Treerat is unique in having shorter and wider incisive foramina with shorter premaxillary septum, less conspicuous grooves on anterior palate, and flatter and broader paroccipital processes. Otherwise, skulls of these two sympatric species are exceedingly similar. Four labial folds are present on dP, M', and M?, with the fourth very small and usually lost with wear. M? usually has only three labial folds or, if four, middle two may coalesce into a Y-branched structure. Chromosomal complement is 2n = 42 and FN = 54.
Habitat. Upland Amazonian rainforest. The Hidden Spiny Tree-rat is arboreal and was collected in trees in terra firma forests, at 1-5, 9-6, and 15-4 m above the ground.
Food and Feeding. Diet and foraging habits of the Hidden Spiny Tree-rat are presumably similar to those ofits close relative, Ferreira’s Spiny Tree-rat. These two species are syntopic, living side-by-side in the same local forests; potential competitive interactions involving space use and food overlap warrant detailed study.
Breeding. A single pregnant Hidden Spiny Tree-rat, captured in June, had a single embryo with crown—rump length of 35 mmActvity patterns. There is no information available for this species.
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. Little is known about the Hidden Spiny Tree-rat, but one locality of occurrence is adjacent to an oil drilling station. There might be opposing negative (habitat loss or degradation) or positive (minimization of whole-sale forest clear-cutting) forces affecting the Hidden Spiny Tree-rat. No protected areas are included in its distribution. Additional studies on distribution, habitat, abundance, ecology, and conservation threats to the Hidden Spiny Tree-rat are needed.
Bibliography. Emmons (2005), Orlando et al. (2003), Patton, Pardinas & D'Elia (2015), Patton, da Silva & Malcolm (2000), Upham et al. (2013), 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 585, DOI: 10.5281/zenodo.6623649