QUATERNARY MURID RODENTS OF TIMOR PART I: NEW MATERIAL OF CORYPHOMYS BUEHLERI SCHAUB, 1937, AND DESCRIPTION OF A SECOND SPECIES OF THE GENUS K. P. APLIN Australian National Wildlife Collection, CSIRO Division of Sustainable Ecosystems, Canberra and Division of Vertebrate Zoology (Mammalogy) American Museum of Natural History ([email protected]) K. M. HELGEN Department of Vertebrate Zoology National Museum of Natural History Smithsonian Institution, Washington and Division of Vertebrate Zoology (Mammalogy) American Museum of Natural History ([email protected]) BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Number 341, 80 pp., 21 figures, 4 tables Issued July 21, 2010 Copyright E American Museum of Natural History 2010 ISSN 0003-0090 CONTENTS Abstract.......................................................... 3 Introduction . ...................................................... 3 The environmental context ........................................... 5 Materialsandmethods.............................................. 7 Systematics....................................................... 11 Coryphomys Schaub, 1937 ........................................... 11 Coryphomys buehleri Schaub, 1937 . ................................... 12 Extended description of Coryphomys buehleri............................ 12 Coryphomys musseri, sp.nov.......................................... 25 Description.................................................... 26 Coryphomys, sp.indet.............................................. 34 Discussion . ..................................................... 40 Species diversity in Coryphomys ....................................... 41 Phylogenetic affinities of Coryphomys ................................... 43 Paleoecology of Coryphomys ......................................... 63 Conclusions....................................................... 68 Acknowledgments.................................................. 69 References........................................................ 69 2 ABSTRACT Large collections of fragmentary animal bones excavated from archaeological contexts in East Timor between 1968 and 2002 provide new material referable to the recently extinct, gigantic murine genus Coryphomys. We document the upper and lower dentition and palatal anatomy of C. buehleri Schaub, 1937, and identify and name a second species of Coryphomys, based on differences in molar size and morphology and skeletal robusticity. Alternative interpretations of the observed morphological and metric variability (sexual dimorphism, resource-based polymorphism, sample heterochroneity) are each carefully assessed and rejected, and we conclude that the genus comprised two species of approximately similar body size. Preserved cranial elements of both species of Coryphomys feature a high degree of anatomical specialization, including an unusual elaboration of the maxillary sinus complex. Though the specialized anatomy of Coryphomys invites consideration of its phylogenetic relationships, this exercise is hindered by a demonstrable high level of homoplasy (i.e., multiple, independent evolutionary losses and gains) in many of the key craniodental features traditionally surveyed within Murinae, while other features are insufficiently well surveyed for broad-scale analysis. Nevertheless, our comparisons highlight two potentially related lineages among the geographically proximate Murinae—the Philippine Phloeomyini and the Australo-Papuan Hydromyini. The remains of Coryphomys are relatively scarce in all the archaeological samples, but distributional evidence suggests that both species of Coryphomys were found primarily in upland habitats. Late Pleistocene samples document their former presence at lower elevations, possibly reflecting cooler climatic conditions at that time. INTRODUCTION the majority of which were subsequently found elsewhere within the Indonesian archi- Timor is located near the eastern end of pelago and beyond (see Goodwin, 1979, for a the Indonesian archipelago and is the largest summary). Indeed, prior to the 1990s, the and highest of the Lesser Sunda Islands only potentially endemic Timorese mammals (fig. 1). The surrounding region is geologi- were two shrews (Crocidura tenuis: treated as cally young and tectonically active, the a synonym of C. fuliginosa [Blyth, 1835] by product of late Tertiary collision between Jenkins [1982] but maintained by Corbet and three major earth units—the Asian and Hill, 1992: 42; and C. macklotti: included Australian continental plates, and the Pacific within C. fuliginosa by Jenkins [1982] but oceanic plate. Plants and animals of Asian considered a synonym of C. tenuis by Corbet and Australian affinities intermingle across and Hill, 1992) and one bat, the enigmatic the region and it was this melding of two such Nyctophilus timorensis (see Goodwin, 1979; different biotas that inspired the nascent Kitchener et al., 1991d, for discussion of this biogeographer Alfred Russel Wallace, and taxon). The impoverished nature of the continues to excite the imagination of stu- Timorese mammal fauna was further high- dents of historical biogeography today. lighted by subsequent discovery through the Timor was one of the first of the Lesser course of the 1900s of endemic nonvolant Sunda Islands to be explored biologically, mammals on Seram and several other Mo- with collections made during the Baudin luccan islands (summarized by Helgen, 2003) expeditions of 1801 and 1803, and subse- and Flores (e.g., Sody, 1941; Kock, 1974). quently by Mu¨ller, Wallace, and others (see More recent surveys of the Lesser Sunda Hellmayr, 1914, and Mayr, 1944, for the Islands, particularly by staff of the Museum history of ornithological collecting). These Zoologicum Bogoriense and the Western expeditions encountered a distinctive avi- Australian Museum (Kitchener and Mar- fauna, including a significant number of yanto, 1993, 1995; Kitchener and Suyanto, endemic species and subspecies. In contrast, 1996; Kitchener et al., 1991a, 1991b, 1991c, the early expeditions encountered a fairly 1991d, 1994), also resulted in discovery of impoverished mammal fauna made up of the several additional endemic mammals includ- familiar suite of domesticates and commen- ing one native rodent extant on Timor, sals, and a moderate number of bat species, Rattus timorensis (Kitchener et al., 1991a). 3 4 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 341 Fig. 1. Regional map showing the location of Timor and other significant islands and continental landmasses of Wallacea. The grey shading indicates the approximate extent of land that is exposed with a sea level depression of 100–120 m below present level. Note that Timor remains isolated from other major islands and continental landmasses during episodes of lowered sea level. The first hint of a much higher endemic for detailed study. Mahoney distinguished a mammalian diversity on Timor came to light total of four large murids including C. during excavations by Alfred Bu¨hler (see buehleri, four smaller native murids, and Sarasin, 1936) in a limestone cave near two commensal murids, the latter found in Nikiniki in southwest Timor. A damaged association with remains of other introduced mandible and an incomplete femur of a very mammals including domesticates, and he large rodent were forwarded to Schaub figured each of the four ‘‘giant’’ rats (Maho- (1937), who described them as a new fossil ney, appendix 3 in Glover, 1986). Musser murid, Coryphomys buehleri. The dental (1981b) examined some of this new material morphology of C. buehleri was later revisited and commented briefly on the possible by Stehlin and Schaub (1951: 348) who affinities of the Timorese rodents, pending regarded the morphology of the anterior publication of Mahoney’s full account. portion of m1 to be unparalleled among Sadly, Mahoney did not complete his studies murines. Not long after, additional Timorese of the Timor rats before his death in 1985. rodent material was recovered by Th. L. Since that time the Glover material has Verhoeven from archaeological contexts at passed through several sets of hands with Lian Leluat on the Maubesi River, southern the intention of completing his work, but so Timor (Verhoeven, 1959). Hooijer (1965) far this goal remains unfulfilled. described and figured a total of three Additional impetus to document the pre- dentaries and though he noted considerable historic Timorese rodents arose after recom- morphological variation, especially in the mencement of archaeological research in East form of the anterior moiety of m1, he Timor in 2000 by archaeologists from the concluded that a single species was repre- Australian National University, Canberra. sented. Excavations in five cave sites, one of them Large samples of prehistoric mammal studied previously by the Portuguese archae- remains from Timor first came available ologist Antonio de Almeida, again produced through archaeological excavations by Ian abundant vertebrate remains from contexts Glover (1986) over the period 1966–1967. ranging from near contemporary back to Glover excavated a total of five sites using more than 38,000 BP (O’Connor et al., 2002; systematic methods and retrieved animal O’Connor and Aplin, 2007; Veth et al., 2005). remains from contexts dated back as far as Our studies of the combined Glover and the terminal Pleistocene. The enormously newly excavated collections inspired a new abundant and surprisingly diverse rodent interpretation of taxic diversity within this specimens were turned over to Jack