A Review of Microhydromys (Rodentia: Murinae), with Description of a New Species from Southern New Guinea

Kristofer M Helgen,Tanya Leary,Kenneth P Aplin

doi:10.1206/632.1

Abstract

The murine rodent genus Microhydromys Tate and Archbold, 1941, includes the smallest of the native rodents of New Guinea and is the rarest Australo-Papuan rodent genus preserved in world museums. We discuss the morphological characteristics of Microhydromys and diagnose two species in the genus: M. richardsoni Tate and Archbold, 1941, distributed over northern New Guinea, and M. argenteus, n. sp., recorded from three localities in southern New Guinea. The only other species previously classified in the genus—Microhydromys musseri Flannery, 1989—is re-allocated to the genus Pseudohydromys Rümmler, 1934. The little available information relating to their biology indicates the species of Microhydromys to be terrestrial inhabitants of foothill and lower montane forest formations and probably naturally rare in those environments.

Highlights

The amphibious “water-rats” and terrestrial “moss-mice” of Australia and New Guinea comprise a distinctive group of nine murine genera endemic to the Australo-Papuan region
Though they span a great range of body sizes, habits, and ecologies, because of similar derivations in craniodental anatomy they have long been regarded as a natural group
Diagnosis: Microhydromys argenteus dif¬ fers externally from M. richardsoni in having paler, uniformly gray-brown pelage, both dorsally and ventrally; a proportionally shorter tail, measuring 91%95% of head-body length (101%—111% of head-body length in M. richardsoni: table 1); a long pale terminal tip, measuring at least one-third of total tail length, with pale mottling extending beyond, to at least to the midpoint of the tail, on both the dorsal and ventral surfaces; and slightly larger hind feet and pinnae

Summary

INTRODUCTION

The amphibious “water-rats” and terrestrial “moss-mice” of Australia and New Guinea comprise a distinctive group of nine murine genera endemic to the Australo-Papuan region All of these genera occur on the island of New Guinea, with Hydromys and Xeromys found in Australia (Flannery, 1995; Hitchcock, 1998) Though they span a great range of body sizes, habits, and ecologies, because of similar derivations in craniodental anatomy they have long been regarded as a natural (monophyletic) group (e.g., Rummler, 1934, 1938; Tate, 1951; Laurie and Hill, 1954; Lidicker, 1968, 1973; Menzies and Dennis, 1979; Flannery, 1995; Helgen, 2005b; cf Breed and Aplin, 1994; Watts and Baverstock, 1994, 1996), a point recently confirmed by a molec¬ ular genetic study of mitochondrial and nuclear gene sequence data from a broad array of Old World murine rodents (Rowe et al, 2008). This approach takes priority at the present time because it is this taxic level that is currently most underestimated in New Guinea mammals (Helgen, 2007), and because taxo¬ nomic overviews are ideally requisite to direct future studies aimed toward better discerning, refining, and testing mammalian patterns of historical biogeography, phylogenetic and ecomorphological diversification, and conserva¬ tion prioritization in the Melanesian region (e.g., Flannery, 1995; Heads, 2001, 2002, Amori et al, 2008; Schipper et al, 2008)

MATERIALS AND METHODS

Findings

DISCUSSION