Euryoryzomys macconnelli (Thomas, 1910)

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 : 44-45

Euryoryzomys macconnelli (Thomas, 1910)

Figures 19A, 19D

VOUCHER MATERIAL (N = 35): Jenaro Herrera (MUSM 16004), Nuevo San Juan (AMNH 268260, 272669, 272675, 272678, 272694, 272696, 272701– 272703, 272711, 273100; MUSM 13321–13325, 13333–13336, 15341, 15342), San Pedro (UF 30485, 30486, 30491, 30493–30495, 30497–30500, 30504, 30505). Additional specimens that we have not examined were reported by Pavlinov (1994) from Jenaro Herera and by Medina et al. (2015) from Quebrada Betilia and Quebrada Lobo.

UNVOUCHERED OBSERVATIONS: None.

IDENTIFICATION: As currently understood, Euryoryzomys macconnelli (formerly Oryzomys macconnelli ; see Weksler et al., 2006) is a widespread Amazonian species that ranges from the Atlantic Ocean to the base of the Andes on both sides of the Amazon River ( Percequillo, 2015a). Although Musser et al. (1998) did not discover any noteworthy geographic variation in morphology among the population samples they examined, Patton et al. (2000) reported phylogenetic analyses of cytochrome b sequence data that suggest the existence of several highly divergent mtDNA lineages, each of which is associated with a different karyotype; these authors recognized a northeastern clade with 2 n = 76 chromosomes, a northwestern clade with 2 n = 58, and a southern clade with 2 n = 64. The type locality of E. macconnelli is in Guyana, so Patton et al.’s northeastern clade would presumably correspond to the nominotypical form (if a trinomial classification were adopted) or to the species in some appropriately restricted sense (if other species were to be recognized in this complex).

Specimens from the Yavarí-Ucayali interfluve closely resemble Euryoryzomys macconnelli as described in detail by Musser et al. (1998: 227– 232). Additionally, measurements of our specimens (table 11) broadly overlap measurements of the type series (Voss et al., 2001: table 33). Despite such qualitative and metrical similarity, an unpublished molecular analysis recently found that cytochrome b sequences obtained from several of our vouchers (AMNH 272669, 272678, 272694; MUSM 13321, 13333) differ from topotypical sequences by>8% ( Martínez, 2021). Although it seems likely that multiple taxa are represented among the geographic forms currently identified as E. macconnelli , we are currently unable to distinguish them morphologically. Additionally, because the available molecular data were obtained from a single mitochondrial gene, and because only a few specimens from widely scattered localities have been karyotyped, we prefer to maintain traditional binomial usage until a formal taxonomic revision is feasible.

Euryoryzomys macconnelli somewhat resembles two sympatric species of Hylaeamys , with which it might be confused. These three species have overlapping measurements (table 11), and they all have soft (nonspinous) fur; large ears (reaching the eye when folded forward); long, narrow hindfeet with unwebbed digits; dense ungual tufts that conceal the claws; and macroscopically naked tails. In dorsal cranial view (fig. 19) they all have long rostrums; deep zygomatic notches; and beaded, anteriorly convergent interorbital regions. In ventral cranial view, they have short incisive foramina; long/wide palates; lowcrowned, pentalophodont molars; narrow parapterygoid fossae; and small auditory bullae. Nevertheless, several morphological characters unambiguously distinguish Euryoryzomys from Hylaeamys (table 12) such that vouchered generic identifications can be made with confidence.

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: Of 22 specimens of Euryoryzomys macconnelli accompanied by ecological informa-