The amphibious murines of New Guinea (Rodentia, Muridae): the generic status of Baiyankamys and description of a new species of Hydromys

Abstract

The amphibious murine rodents of New Guinea have traditionally been classified in three genera: Hydromys E. Geoffroy, 1804, Parahydromys Poche, 1906, and Crossomys Thomas, 1907. Species currently classified in Hydromys can be further divided into two cladistic groups: species distributed in lowland habitats (below 2000 m) with glossy, dark brown dorsal pelage, and species restricted to upper montane rivers and lakes (generally above 2000 m) with soft, silvery grey dorsal pelage. These two groups differ not only in pelage traits and habitat association but also in craniodental and phallic anatomy. The generic-level name Baiyankamys Hinton, 1943, is resurrected for the latter cluster (which includes two species, B. shawmayeri of eastern New Guinea and B. habbema of west-central New Guinea). Additionally, a new species of Hydromys (H. ziegleri n. sp.) is described from the southern foothills of the Prince Alexander Range of Papua New Guinea. Mammalian zoogeography in the North Coast Ranges, an area of considerable geographicallyrestricted mammalian endemism, is reviewed.

Systematic Review of New Guinea Leptomys (Muridae, Murinae) with Descriptions of Two New Species

“…Neither endeavor recovered Leptomys, although these undertakings are unlikely to represent a comprehensive inventory of small mammals in the region (Helgen, 2007a(Helgen, , 2007b. Currently, forested habitats at lower altitudes in the Vogelkop remain comparatively poorly surveyed for mammals (Aplin et al, 1999;Helgen, 2005bHelgen, , 2007aHelgen, , 2007b, and we suspect that, as for L. elegans and L. signatus, it is lowland and hill forest formations and the lower montane forest ecotone that will prove to be the preferred habitats of L. arfakensis.…”

“…It is the only hydromyin genus (cf. Helgen, 2005b) that retains third molars; all others in that group possess only first and second molars (or only first molars in Pseudohydromys ellermani). Within Leptomys, however, L. arfakensis demonstrates the greatest dental reduction.…”

“…Whether Paraleptomys and Leptomys are phylogenetically related or not (Musser and Carleton, 2005), we suspect that their close ecomorphological resemblance may partly explain their intriguing geographic patterning. Perhaps because of their ecological similarity, species of Paraleptomys and Leptomys appear to replace each other in checkerboard fashion on mountain ranges lying north of the Central Cordillera, with Leptomys in the Arfaks, Fojas, Adelberts, and Huon Ranges, and Paraleptomys in the Cyclops, Bewani, and Torricelli Ranges (see Helgen, 2005b, andDiamond, 1985). They also appear to replace each other in an eastwest fashion along the Central Cordillera, with Leptomys in the Owen Stanley Range and in the eastern and central highlands in the eastern region of the Cordillera, and Paraleptomys in the Star and Snow mountains in the west.…”

“…The Arfaks themselves, although better surveyed than other highlands on the Vogelkop, probably also support many other species that remain currently undetected. We suspect that these might include small amphibious murines and tiny terrestrial moss mice, both of which are present throughout other montane areas of New Guinea but can be challenging to collect without pitfall techniques, which have only rarely been used to collect mammals in New Guinea (Flannery, 1995;Helgen, 2005bHelgen, , 2007a. Future systematic collecting of small mammals along altitudinal gradients in the Arfaks and other Vogelkop Ranges will be needed to more definitively characterize the true geographic distribution and habitat associations of L. arfakensis.…”

“…These, in combination with Leptomys, are at the heart forming the iconography of endemic AustraloPapuan murids. Identified informally as a recognizable group or formally as tribe, subfamily, or even family (Flannery, 1995;Helgen, 2005bHelgen, 2007aMusser and Carleton, 2005;Tate, 1951), members of this assemblage are primarily carnivorous and demonstrate a remarkable evolutionary radiation in geographic isolation that resulted in adaptive morphologies ranging from amphibious to shrewlike ecologies. The cladistic position of Leptomys within this assemblage is the subject of inquiries to be completed at a later time.…”