Abstract
Recognition and identification of red-rumped mice of the genus Juliomys Gonzalez, 2000 has been a problem among many mammalogists, and specimens of this genus are commonly confused with other Atlantic Forest sigmodontine rodents. Herein we provide an expanded diagnosis for the genus based on the analyses of the three living species of Juliomys, and provide morphological comparisons to the small bodied and bright colored rodents Rhagomys rufescens (Thomas, 1886) and Oligoryzomys flavescens (Waterhouse, 1837), which occur in sympatry with Juliomys spp. in forested areas of southeastern Brazil. These taxa are superficially similar, and are therefore commonly misidentified in the field and museum collections. We also provide morphometric data and a key to the living species of Juliomys, and an updated distribution map of the genus and its species.
Highlights
Juliomys González, 2000 is currently composed of three living species and is endemic to the Atlantic Forest of southeastern Brazil, northeastern Argentina and eastern Paraguay (DE LA SANCHA et al 2009)
Recognition and identification of red-rumped mice of the genus Juliomys González, 2000 has been a problem among many mammalogists, and specimens of this genus are commonly confused with other Atlantic Forest sigmodontine rodents
We provide an expanded diagnosis for the genus based on the analyses of the three living species of Juliomys, and provide morphological comparisons to the small bodied and bright colored rodents Rhagomys rufescens (Thomas, 1886) and Oligoryzomys flavescens (Waterhouse, 1837), which occur in sympatry with Juliomys spp. in forested areas of southeastern Brazil
Summary
Members of Juliomys can be distinguished from R. rufescens mainly by: a darker fur, with rump and hind legs distinctly orange, contrasting with the rest of the body; this contrast is not observed in Rhagomys Thomas, 1917, which shows a more homogeneous bright orange fur (Figs 1-3); tips of ventral hairs whitish to light-brown instead of orange; four pairs of mammae instead of three; slightly longer hindfeet, with smaller and narrower interdigital pads (Figs 46); hindfeet bearing a projecting claw on the first digit, instead of a round claw, resembling a nail; skull smaller, slender and more delicate (Figs 7-9); rostrum, interorbital region and zygomatic plate narrower; parapterygoid plate wider; anterior margin of mesopterygoid fossa reaching M3, while in Rhagomys, this structure does not reach M3; dentary smaller (Figs 10-12), and molar cusps less conspicuous. Dorsal (above) and ventral (below) views of the skulls of: (7) Juliomys pictipes (UFMG 3165); (8) Oligoryzomys flavescens (UFES 1177); (9) Rhagomys rufescens (AB 401).
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