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| Baletemys kampalili Rowsey, Duya, Ibañez, Jansa, Rickart & Heaney, 2022 Illustration by Velizar Simeonovski, based on holotype [FMNH 208788]. |
Abstract
The Philippine archipelago hosts an exceptional diversity of murid rodents that have diversified following several independent colonization events. Here, we report the discovery of a new species of rodent from Mt. Kampalili on eastern Mindanao Island. Molecular and craniodental analyses reveal this species as a member of a Philippine “New Endemic” clade consisting of Tarsomys, Limnomys, and Rattus everetti (tribe Rattini). This new species of “shrew-mouse” is easily distinguished from its relatives in both craniodental and external characteristics including a long, narrow snout; small eyes and ears; short, dark, dense fur dorsally and ventrally; stout body with a tapering, visibly haired tail shorter than head and body length; stout forepaws; bulbous and nearly smooth braincase; narrow, tapering rostrum; short incisive foramina; slender mandible; and narrow, slightly opisthodont incisors. This new genus and species of murid rodent illustrates that murids of the tribe Rattini have exhibited greater species and morphological diversification within the Philippines than previously known and provides evidence that Mt. Kampalili represents a previously unrecognized center of mammalian endemism on Mindanao Island that is deserving of conservation action.
Keywords: biogeography, conservation, diversification, endemism, montane forest, mossy forest, Mt. Kampalili, oceanic island, taxonomy
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| Baletemys kampalili based on FMNH 208788, holotype. Illustration by Velizar Simeonovski |
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| Dorsal, ventral, and lateral views of (A) Baletemys kampalili FMNH 208788 compared to (B) Tarsomys apoensis FMNH 148176, (C) Limnomys sibuanus FMNH 148174, and (D) Rattus everetti FMNH 206290. Approximately life size. |
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| Dorsal, ventral, and lateral views of Baletemys kampalili FMNH 208788. Approximately times 2.5 magnification. |
Baletemys, new genus
Type species: Baletemys kampalili, new species described below.
Diagnosis: Phylogenetically defined as a member of the endemic Philippine Tarsomys clade of Tribe Rattini in family Muridae (Figs. 3 and 4), distinguished by the following combination of traits: Intermediate in size, ca. 70 g in weight and 135 mm head and body length (Table 2); shrew-like in appearance (Fig. 2), with soft, dense fur, small eyes and ears, and a conical head with a narrow snout; pelage dark russet brown dorsally with moderately sparse guard hairs, and dark grayish ochre ventrally; mystacial vibrissae long, up to ca. 50 mm, reaching beyond tip of ear; two pairs of inguinal mammae; tail proportionally short (74% of HBL), ca. 100 mm, unicolor, and densely covered in dark umber (almost black) hairs both dorsally and ventrally that partially obscure the scales on the tail; claws on manus unusually robust and long, with a nail-like claw on the hallux. Skull (Fig. 7) slender and elongate; incisors slightly opisthodont, nongrooved, and narrow (0.84–0.94 mm wide and 2.00–2.08 mm deep); rostrum long, narrow, and tapering; zygomatic plate narrow, about twice the width of zygomatic arches; orbitotemporal opening proportionally small, with zygomatic arches short and slightly thinner than in other comparably sized Philippine murids, ca. 0.60–0.70 mm at narrowest point (Table 3); descending (anterior) portion of zygomatic arch at shallow angle with respect to dorsal surface of skull, and with lowest extent terminating above the palate. Braincase long and narrow anteriorly but widening posteriorly, smooth and ellipsoidal, without prominent temporal ridges, supraoccipital ridge nearly absent; maximum width of braincase nearly as wide as zygomatic arches; carotid artery with stapedial and internal branches, the former feeding laterally into the otic capsule through a stapedial foramen, and the latter entering the auditory bulla through a foramen adjacent to the basioccipital shelf (see Fig. 56D in Musser and Heaney 1992); auditory bullae weakly inflated compared to its relatives; pterygoid fossa shallow, nearly flush with the plate formed by the basisphenoid and basioccipital bones; medial lacerate and postglenoid foramina continuous or nearly so; incisive foramina short and narrow, terminating 0.65–1.25 mm anterior to molar rows; posterior margin of bony palate extending slightly beyond posterior margins of third molars. Labial cusp t3 elongated into lamina that is mostly continuous with t2 (Fig. 8); labial cusp t3 on M2 tiny but present; lingual cusp t7 and posterior cingulum absent from all upper molars; posterior labial cusplet on m1 and m2 absent. Mandible slender, with angular and condyloid processes approximately equal in length (Fig. 7).
Etymology: We combine the Greek “mys” (mouse) with “Balete,” in honor of the late Danilo S. Balete, whose extensive contributions to understanding Philippine biodiversity, with particular respect to its mammals, were instrumental in characterizing the Philippines as an exceptionally rich center of endemic mammalian diversity, as well as providing exemplary leadership in mentoring of young colleagues and in promoting conservation of the fauna.
Baletemys kampalili, new species
Etymology: This species is named for Mt. Kampalili, where all specimens have been obtained. The specific epithet is used as a noun in apposition.
We suggest “Kampalili shrew-mouse” or “Kampalili baletemys” as the English common name.
Geographic distribution: Known only from two localities, about 6 km apart, on the southern slopes of Mt. Kampalili, but probably widely distributed above 1,450 m on the peaks surrounding Mt. Kampalili (Fig. 1).
Dakota M. Rowsey, Mariano Roy M. Duya, Jayson C. Ibañez, Sharon A. Jansa, Eric A. Rickart and Lawrence R. Heaney. 2022. A New Genus and Species of Shrew-like Mouse (Rodentia: Muridae) from A New Center of Endemism in eastern Mindanao, Philippines. Journal of Mammalogy. gyac057. DOI: 10.1093/jmammal/gyac057
