Pseudohydromys Rümmler 1934

Pseudohydromys Rümmler 1934, Z. Saugetierk., 9: 47.

Type Species: Pseudohydromys murinus Rümmler 1934

Synonyms: Mayermys Laurie and Hill 1954; Neohydromys Laurie 1952 .

Species and subspecies: 4 species:

Species Pseudohydromys ellermani Laurie and Hill 1954

Species Pseudohydromys fuscus Laurie 1952

Species Pseudohydromys murinus Rümmler 1934

Species Pseudohydromys occidentalis Tate 1951

Discussion: Xeromys Division. Member of the New Guinea Old Endemics (Musser, 1981 c). Species of Pseudohydromys, Neohydromys, and Mayermys are all terrestrial, primarily insectivorous, small-bodied shrew mice living in mountain forests of New Guinea. They share dense, velvety fur, generally similar cranial conformation (see photographs in Laurie and Hill [1954] and Flannery [1995 a:plates 22-23]), spacious postglenoid and middle lacerate foramina, derived configuration of cephalic arterial pattern (Musser and Heaney, 1992), loss of third molars ( Pseudohydromys, Neohydromys) or second and third molars ( Mayermys), dentary shape and degree of penetration of incisor alveolus, extent of enamel relative to dentine on upper and lower incisors, similar phallic morphology (Lidicker, 1968) and spermatozoal structure (Breed and Aplin, 1994), and no divergence in immunological distance (albumins indistinguishable among the three as assessed by microcomplement fixation of albumin; Watts and Baverstock, 1994 a). Species in the three genera clearly form a tight monophyletic group that should be taxonomically expressed by uniting Neohydromys and Mayermys with Pseudohydromys . In proposing Neohydromys, Laurie (1952:311) compared it to Microhydromys, another small-bodied shrew mouse, which has no close morphological relationship to Pseudohydromys, Neohydromys, or even Mayermys (see generic account of Microhydromys). Morphological contrasts between Neohydromys fuscus and Pseudohydromys murinus presented by Laurie are of the magnitude typical of interspecific variation seen in other murine genera. With its flatter cranium and loss of second and third molars, Mayermys ellermani stands apart from the other species, but these are autapomorphies within the monophyletic cluster. Judged by albumin immunology (Watts and Baverstock, 1994 a, 1996) and spermatozoal morphology (Breed, 1997; Breed and Aplin, 1994), Pseudohydromys is part of a larger clade containing species in our Hydromys, Xeromys, Pseudomys, and Uromys Divisions (the "Australasian clade" of Watts and Baverstock, 1995 b, 1996).