A new species of Thomasomys Coues, 1884 (Rodentia: Sigmodontinae) from the montane forests of northern Peru with comments on the “aureus” group

Dennisse Ruelas,Víctor Pacheco

doi:10.15381/rpb.v28i3.19912

Abstract

We describe a new species of the cricetid rodent Thomasomys (Sigmodontinae) of the "aureus" group based on four specimens collected from Carmen de la Frontera, Piura Department, Peru. This new species has a very long and white tail, very long mystacial vibrissae that extend posteriorly beyond the pinnae, and a distinctive cranial and dental morphology that differ from any other known species of Thomasomys. It is also one of the largest species of Thomasomys, exceeded in size only by T. apeco. A phylogenetic analysis using sequences of Cytb recovered this species within a non-monophyletic "aureus" group with a genetic distance between 5.47% (with T. auricularis) to 10.17% (with Thomasomys sp. 1). In addition to this finding, the phylogenetic position of T. apeco, T. praetor, and T. pyrrhonotus are presented for the first time, prompting a discussion on the nature of the "aureus" group.

Highlights

Divergence of the new species respect to another species of the "aureus" group (5.47 % - 10.17 %) fits the threshold of interspecific variation (Baker & Bradley 2006), similar to distances previously found among Thomasomys species using cytochrome b (Cytb) (e.g., Salazar-Bravo & Yates 2007, Brito et al 2019, 2021)
Thomasomys antoniobracki sp. nov. is currently considered an endemic species from the montane forest of northern Peru and known only for the type locality
Other Thomasomys species recorded with T. antoniobracki sp. nov. are T. caudivarius Anthony, 1923, T. taczanowskii (Thomas, 1882), and T. cf. vulcani

Summary

Introduction

The genus Thomasomys Coues, 1884 is one of the most specious genera of the subfamily Sigmodontinae comprising 46 recognized species (Pacheco 2015, Brito et al 2019, Brito et al 2021); morphological and molecular evidence suggests that diversity is underestimated (Pacheco 2003, 2015, Lee et al 2015, Brito et al 2019). Thomasomys is endemic to South America in tropical and subtropical habitats and distributed along the Andes in paramo, premontane, and montane forests from northern Venezuela to southern Bolivia, including isolated ranges such as the Serranía de la Macarena in Colombia, at an elevational range of about 1200 m to above 4500 m (Pacheco 2015); and isolated cordilleras like El Cóndor and Kutukú, in Ecuador (Brito et al 2021). Seven informal species groups have been defined (Pacheco 2015), of which the "aureus" group includes mainly medium and the larger rodents in the genus (head and body length: 135–238 mm) distributed throughout the montane forests from Venezuela and Colombia to southeastern Bolivia. This group was represented by few species (e.g., Salazar-Bravo & Yates 2007a, Lee et al 2015, 2018a, Brito et al 2019)

Methods

Results

Conclusion