Ziegler's Hydromys

description

Description: The holotype of ziegleri is smaller than most specimens of hussoni (Figs. 3 – 4; Table 3). The dorsal pelage of ziegleri is dark brown (somewhat darker than the rich brown of hussoni) tipped with paler, orange­buff hairs. The fur is considerably shorter (6 – 7 mm on the anterior dorsum), less dense, and conspicuously more glossy than in hussoni. The fur of the venter is grey­based with ochraceous­buff tipping, similar to hussoni (Musser and Piik 1982; Ziegler 1984), but in the holotype of ziegleri the lower cheeks and the underside of the throat and chin are dingy white, contrasting with the rest of the venter. The inguinal region and ventral base of the tail are dark brown (Figure 3). As in other Hydromys, the hindfeet are long and broad and bear conspicuous webbing between the middle digits (II – IV). The dorsal surface of the pes is pigmented dark but covered with small pale hairs, and the claws are equal in size to those of hussoni, and unpigmented. The skin label gives the hindfoot length as 29, probably measured with the claw, as on the dry skin this length is closer to 27 sans unguis (Ziegler 1984). The tail of the holotype is black, and lacks a white tail­tip,

the generic status of Baiyankamys and description of a new species of Hydromys

description

During cooler climatic periods during the Late Pleistocene, montane forests extended to much lower elevations in New Guinea than they do today, and the montane­adapted species of the North Coast Ranges likely had considerably more expansive or even contiguous distributions across certain of these mountain ranges. I suspect that the seemingly haphazard distribution of endemic species recorded from the various North Coast ranges today (Table 5) reflects a combination of two factors: artefacts of geographically uneven sampling effort and, at least for some of the larger­bodied species (Zaglossus, Dendrolagus), historical extinctions (see Flannery et al. 1996; Flannery and Groves 1998). Some of the larger endemic mammals of the North Coast Ranges, especially Zaglossus attenboroughi, Dendrolagus scottae, and Dendrolagus pulcherrimus, have minuscule global geographic ranges and are actively hunted for food (Flannery et al. 1996; Flannery and Groves 1998), and are probably among the most endangered of all Australasian mammals (indeed, Z. attenboroughi may already be extinct; Flannery and Groves 1998). All North Coast Range endemic mammals, even the smallest (such as ‘ Microhydromys’ musse

the generic status of Baiyankamys and description of a new species of Hydromys

diagnosis

Diagnosis: Hydromys ziegleri is the smallest species of Hydromys. It most closely resembles H. hussoni, endemic to the upland Wissel Lakes of west­central New Guinea (Figs. 3 – 4; Table 3 – 4), but differs from that species in its smaller size, broadened rostrum, shorter incisive foramina, shorter toothrow, broader first molars, lower­domed braincase, and much less densely­furred tail.

the generic status of Baiyankamys and description of a new species of Hydromys

distribution

Distribution: Hydromys ziegleri is known only from the type locality, situated in the foothills of the southern slopes of the Prince Alexander Range, one of the North Coast Ranges of Papua New Guinea. The type locality lies in the vicinity of the Screw and Amuk Rivers, which drain from the highlands of the Prince Alexander Range and the Torricelli Range, respectively. I suspect that future collecting efforts may show it to occur more widely (and at higher altitudes) in the North Coast Ranges (see Discussion below). Two other amphibious murines (Hydromys chrysogaster and Parahydromys asper) are known from other localities in the North Coast Ranges and are thus likely to occur sympatrically with H. ziegleri, though only H. chrysogaster has been collected in the same general area to date (e. g. CSIRO 8346, adult male from Maprik).

the generic status of Baiyankamys and description of a new species of Hydromys