A new species of Leaf-eared Mouse, genus Phyllotis Waterhouse, 1837 (Rodentia: Cricetidae) from northern Peru

PACHECO, V.; RENGIFO, E.M.; VIVAS, D. 2014. A new species of Leaf-eared Mouse, genus Phyllotis Waterhouse, 1837 (Rodentia: Cricetidae) from northern Peru. THERYA 5(2):481-508. doi: 10.12933/therya-14-185

Abstract.
Introduction: Leaf-eared mice, Phyllotis comprise a highly species-rich genus distributed in the Andes of South America from sea level to 5,500 m. This genus includes 15 species in three groups: andium/amicus, osilae, and darwini groups (sensu Steppan et al. 2007). We describe a new species of rodent of the genus Phyllotis from the northern Peruvian Andes, which has been mentioned in the literature as Phyllotis sp. nov. 1 or Phyllotis sp. and placed, in the context of a molecular phylogeny of Phyllotis, as member of the P. andium/amicus group (Steppan et al. 2007). We also report the standard karyotype of this species and comment on its natural history. We further identify an area of endemism in the northwestern Andes of Peru, where the new species and other sigmodontines coincide in patterns of distribution.
Methodology: The new species was in detail compared with other species of Phyllotis, mainly those of the andium/amicus group. Four external and 20 cranial and dental measurements from adult specimens were employed in descriptive statistics. Sexual dimorphism was evaluated in Phyllotis nov. sp. and P. andium using the t test. Then, to compare the new species with P. andium, all cranial and dental measurements were used in principal component analyses (PCA) of the covariance matrix of log-transformed measurements. Chromosome preparations were obtained from bone marrow, following Ford and Hamerton (1956).
Results: Phyllotis nov. sp. is distinguished from all other congeneric species by the combination of a relatively short tail and distinctive cranial morphology, including an comparatively long incisive foramen, a long palate that extends posteriorly beyond M3, mesopterygoid fossa without medial process, squamosal ridge relatively pronounced, ectotympanic large and easily visible from dorsal view, and capsular process inconspicuous or absent. The biplots of PCA show two clearly separated groups, one shaped by specimens of the new species and the other by P. andium; the new species is located mainly on the positive side of the first axis whereas P. andium on the negative side. The diploid number (2n) is 48 and the autosomal fundamental number (FN) is 72.
Discussion and conclusions: The new species of Phyllotis is endemic to the Puna ecoregion of northern Peru. This discovery supports the hypothesis of a generalized biogeographical subdivision in the Puna of northwestern Peru where the ranges of several sigmodontine species coincide in an area limited by the Río Santa, the Río Marañón, and the Huancabamba depression. Based on the presence of numerous crocentric chromosomes and the available molecular data we propose a restricted andium group to include P. andium, P. definitus, and the new species. We also summarize available data on natural history, habitat preferences, reproduction, and the systematic position of this species. The species may be threatened due to its restricted distribution, the relatively high anthropic activity in the region, and its absence in any protected area.

External features of the dusk dolphin Lagenorhynchus obscurus (Gray, 1828) from Peruvian waters

WAEREBEEK, K.V. 1993. External features of the dusk dolphin Lagenorhynchus obscurus (Gray, 1828) from Peruvian waters. Estudos Oceanológicos 12:37-53.

Abstract. Individual, sexual and developmental variation is quantified in the external morphology and colouration of the dusky dolphin Lagenorhynchus obscurus from Peruvian coastal waters. No significant difference in body length between sexes is found (p = 0.09) and, generally, little sexual dimorphism is present. However, males have a more anteriorly positioned genital slit and anus and their dorsal fin is more curved, has a broader base and a greater surface area than females Although the dorsal fin apparently serves as a secondary sexual character, the use of it for sexing free-ranging dusky dolphins is discouraged because of high overlap in values. Relative growth in 25 body measurements is characterized for both sexes by multiplicative regression equations. The colouration pattern of the dorsal fin, flank patch, thoracic field, flipper stripe and possibly (X², p = 0.08) the eye patch, are independent of maturity status. Flipper blaze and lower lip patch are less pigmented in juveniles than in adults No sexual dimorphism is found in the colour pattern The existence of a discrete "Fitzroy" colour form can not be confirmed from available data. Various cases of anomalous, piebald pigmentation are described, probably equivalent to so-called partial albinism. Adult dusky dolphins from both SW Africa and New Zealand are 8-10 cm shorter than Peruvian specimens, supporting conclusions of separate populations from a recent skull variability study.