Mesomys hispidus (Desmarest, 1817)

Voss, Robert S., Fleck, David W. & Jansa, Sharon A., 2019, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 5. Rodents, Bulletin of the American Museum of Natural History 2024 (466), pp. 1-180 : 124-126

Mesomys hispidus (Desmarest, 1817)

Figure 52

VOUCHER MATERIAL (N = 9): Nuevo San Juan (AMNH 268252, 268269, 273080; MUSM 13306, 15328, 15329), San Pedro (MUSM 22346, UF 30599), Santa Cecilia (FMNH 87242).

UNVOUCHERED OBSERVATIONS: None.

IDENTIFICATION: Like other species of Mesomys (see below), the specimens that we refer to

M. hispidus are small echimyines (HBL <200 mm) with conspicuously spiny, uniformly grizzled-brownish dorsal pelage and a sparsely haired tail with an obvious terminal tuft. The forefeet are mesaxonic (digits III and IV are equal in length), and manual digits II–V have strong, sharp claws. The upper cheektooth rows are approximately parallel (not strongly convergent anteriorly), and the upper cheekteeth (unlike those of other echimyines in our region) have closed labial flexi that are isolated as enamel islands on the occlusal surface, being essentially similar in this respect to the cheekteeth of Proechimys .

As currently recognized, Mesomys hispidus is a widespread Amazonian species that exhibits substantial geographic variation in size and mtDNA sequence characteristics ( Patton et al., 2000; Orlando et al., 2003; Patton and Emmons, 2015b). Phylogenetic analyses of cytochrome b sequence data obtained from two of our vouchers (MUSM 13306, 22346) recovered both as members of “Clade A,” a strongly supported haplogroup that included other sequences from eastern Peru and western Brazil ( Orlando et al., 2003). 37 By contrast, a cytochrome b sequence obtained by the same authors from Desmarest’s centuries-old holotype (MNHN 1998-2075) was recovered within “Clade F,” a haplogroup composed of sequences from French Guiana that differ from those in Clade A by about 7% in model-corrected (K2P) comparisons. Among other evidence of phenotypic divergence between these lineages, the maxillary toothrow length of specimens in Clade A is 7.3 ± 0.2 mm, whereas the maxillary toothrow of specimens in Clade F is 6.2 ± 0.2 mm ( Orlando et al., 2003: table 2). Measurements of our specimens (table 37) broadly overlap those of others assigned to Clade A (e.g., the “upriver clade” of Patton et al., 2000:

37 In Orlando et al.’s (2003: fig. 2) phylogeny MUSM 13306 was mislabelled as having come from Cusco department, although its correct provenance was given in one of their appendices ( Orlando et al., 2003: 120). The sequence that they identified as MV970002 (Michael Valqui’s field number) corresponds to the specimen now cataloged as MUSM 22346).

table 58), which they likewise resemble in qualitative traits.

The oldest available junior synonym of Mesomys hispidus (sensu Patton and Emmons, 2015b) with a type locality adjacent to the known range of Clade A is ferrugineus Günther, 1876 , the description of which was based on a specimen collected about 240 km west of our region at Chamicuros (on the lower Río Huallaga at 5°30′S, 75°44′W; Moncrieff et al., 2019). On a 1998 visit to London, R.S.V. measured Günther’s damaged type (BMNH 69.3.31.8), the intact dimensions of which (LD, 9.0 mm; MTR, 7.5 mm; LIB, 10.8 mm; ZB, 22.6 mm) are all within the range of morphometric variation in Clade A as documented in the references cited above. Although Thomas (1911: 607) thought that Günther’s ferrugineus “cannot be separated” from ecaudatus Wagner, 1845 (another junior synonym of M. hispidus as currently recognized), the type locality of ecaudatus (Borba, at 4°24′S, 59°35′W, on the right bank of the lower Rio Madeira; Paynter and Traylor, 1991) is over 1000 km distant from the known range of Clade A, and it is on the opposite side of a known biogeographic barrier.

Thus, Mesomys ferrugineus would seem to be the appropriate name for Clade A (including our specimens from the Yavari-Ucayali interfluve) if additional taxa were to be recognized as valid within the M. hispidus complex. As others before us (e.g., Orlando et al., 2003) have concluded, however, it seems prudent to await additional analyses based on nuclear loci, karyotypes, and more densely sampled phenotypic data before disrupting the taxonomic status quo.

ETHNOBIOLOGY: The Matses have no special name for this species.

MATSES NATURAL HISTORY: No interviews were focused on this species.

REMARKS: Six specimens of Mesomys hispidus are accompanied by habitat information from our region. Of these, one dropped from a tree that was being felled for a new swidden in primary upland forest, four were shot at night from trees in primary floodplain (seasonally inundated) forest, and one was trapped on a liana in open hillcrest forest. Recorded heights from which specimens were shot or trapped ranged from 1 to 10 m above the ground. Sparse as they are, these data are consistent with observations previously summarized by Emmons (1997) and Patton et al. (2000) that M. hispidus is a eurytopic arboreal species.