Neacomys aletheia Semedo et al., 2021

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 : 51-53

Neacomys aletheia Semedo et al., 2021

Figure 21A, 21D

VOUCHER MATERIAL (N = 17): Jenaro Herrera (AMNH 276724; MUSM 5457, 15993–15995, 23812, 23813), Nuevo San Juan (AMNH 272867, 272869, 273053; MUSM 13309, 13311–13314,

15330, 15331). Additional material originally reported as Neacomys minutus by Medina et al. (2015) from Quebrada Betilia and Quebrada Pantaleón was subsequently identified as N. aletheia by Sánchez-Vendizú et al. (2021).

UNVOUCHERED OBSERVATIONS: None.

IDENTIFICATION: Neacomys aletheia is one of two distinctively small (<20 g) congeneric species that occur sympatrically in the Yavarí-Ucayali interfluve. The other small species in our region, N. musseri , is so similar to N. aletheia in size and pelage coloration that these species are perhaps externally indistinguishable, and our series likewise overlap in all measured craniodental dimensions (table 15). Apparently, the only morphological character by which N. aletheia and N. musseri can be unambiguously distinguished concerns the carotid circulation. Whereas N. aletheia retains the supraorbital branch of the stapedial artery—which leaves a translucent groove along the inner surfaces of the squamosal and alisphenoid bones and exits the skull via the sphenofrontal foramen (pattern 1 of Voss, 1988: 297–298)— N. musseri lacks the supraorbital branch and both of its osteological markers (pattern 2 of Voss, 1988). Neacomys aletheia was previously known as the “upriver clade” of N. minutus by Patton et al. (2000), who documented its substantial molecular and karyotypic divergence from N. musseri .

Phylogenetic analyses of cytochrome b sequences obtained from our voucher specimens confirm their identity with the “upriver clade” of Neacomys minutus (sensu Patton et al., 2000) and with the species subsequently named as N. aletheia . Those analyses ( Sánchez-Vendizú et al., 2018; Semedo et al., 2021) additionally suggest that the sister taxon of N. aletheia is N. macedoruizi , a species that occurs on the north bank of the Amazon, rather than with N. minutus sensu stricto (the “downriver clade” of Patton et al., 2000). Morphological, molecular, and karyotypic comparisons of N. aletheia (as the “upriver clade” of N. minutus ) and N. macedoruizi were summarized and discussed by Sánchez-Vendizú et al. (2018). Measurements of our specimens from the Yavarí-Ucayali interfluve are indistinguishable from those of the type series of N. aletheia from the Rio Juruá in western Brazil (table 15).

ETHNOBIOLOGY: This species is not known to the Matses, who have no special name for it.

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

REMARKS: Thirteen specimens of Neacomys aletheia are accompanied by habitat information from our region. Of these, seven were taken in primary upland (well-drained) forest, one was taken in swampy primary forest, one was taken in primary forest of unspecified type, three were taken in secondary vegetation (abandoned swiddens), and one was taken in an active swidden. Ten specimens were trapped on the ground, but three were taken on elevated substrates near ground level (lianas or fallen branches). Most specimens were captured in Sherman traps, but three were taken in pitfalls, two were caught by hand, and one was taken in a deadfall set for Proechimys (see below). Two specimens accompanied by microhabitat descriptions were both taken in open hilltop primary forest, one under sparse leafy cover and the other beneath a tangle of fallen branches and dead palm fronds.