Philippine rodents : redefinitions of known species of Batomys (Muridae, Murinae) and description of a new species from Dinagat Island. American Museum novitates ; no. 3237

Abstract

51 p. : ill. ; 26 cm.Includes bibliographical references (p. 49-51)."Batomys russatus, new species, is described and compared with the other species of Batomys. The new form is represented by three specimens collected in lowland tropical evergreen rainforests on Dinagat (10 degrees N, 125 degrees 45'E), an elongate, mountainous small island off the northwest coast of Mindanao in the Philippine Archipelago. Among diagnostic traits of the new species are its small body size, colorful russet fur, and complete (primitive) cephalic arterial patterns- in this last feature, it is unique among species of extant murines. Three other species of Batomys have been described, all of them larger-bodied animals with somber brown fur and a derived cephalic arterial circulation. All available specimens (N = 162) of these larger-bodied species were studied to reevaluate morphological and distributional species boundaries. Among the three, B. dentatus is the most distinct. Represented only by the holotype collected in the highlands of Luzon, it is the only known Batomys with a furry brown-and-white tail and exceptionally large molars, both in absolute measurements and relative to cranial size. Batomys granti also occurs in the mountains of Luzon, but it is morphologically very similar to B. salomonseni, which is now represented by samples from the islands of Mindanao, Leyte, Biliran, and Dinagat. These two species differ in tail diameter and pilosity, hind foot configuration, cranial proportions, and frequency of certain molar cusps. The new Batomys is one of 29 native mammal species currently documented from Dinagat by voucher specimens. It and another rodent, Crateromys australis, along with the insectivore Podogymnura aureospinula- approximately 10% of the mammalian fauna- have been found only on Dinagat. Other species native to the island either occur on nearby islands that were apparently joined during the late Pleistocene to form a larger land area (Greater Mindanao), or are found throughout the Philippine Archipelago and even in adjacent regions outside the Philippines. Within the Greater Mindanao cluster of islands, only Mindanao, the largest, has a proportion of endemic mammalian species comparable to that on the much smaller Dinagat; the other islands lack endemics altogether. Why this is so is unknown"--P. 2