Tenrecidae , Insectivora
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NovtautesAMERICAN MUSEUM PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2889, pp. 1-45, figs. 1-13, 5 tables September 2, 1987 The Shrew Tenrecs of Madagascar: Systematic Revision and Holocene Distribution of Microgale (Tenrecidae, Insectivora) R. D. E. MACPHEE' ABSTRACT The shrew tenrecs of Madagascar-Microgale Revision permits, for the first time, an approx- and the allied nominal genera Leptogale, Para- imate idea of the true ranges and habitat prefer- microgale, and Nesogale-have never been for- ences of shrew tenrec species. Although the ma- mally revised. Examination of all relevant type jority of species appear to be restricted to the material reveals that only 10 of the 22 nominal comparatively moist and equable conditions ofthe species-group names ofshrew tenrecs deserve rec- eastern rain forest, several species occur in forest ognition. The large number of synonyms is prin- islands and other favorable habitat in the eastern cipally due to authors' repeated commission of part of the highlands, and two (M. pusilla and two substantial errors: (1) failing to recognize the brevicaudata) have occupied the dry, highly sea- juvenile status of many "adult" specimens used sonal western side of the island in recent times. as holotypes, and (2) failing to appreciate the Despite its morphological primitiveness, Micro- marked degree of within-group variation in these gale can be aptly described as adaptively resilient. insectivores. Analysis of a range of metric and Colonization of the highlands and the far west nonmetric traits further reveals that there are only presumably occurred by pioneering groups mov- three or four distinctively different morphological ing out from the eastern forest belt during times clusters of shrew tenrecs in the modern fauna, and ofclimatic amelioration and forest expansion; iso- that all species clusters can be comfortably accom- lation of these groups would have occurred when modated in one genus, Microgale. Illustrations of conditions deteriorated in the center. Emigration deciduous and adult dentitions and a key to rec- events could have occurred repeatedly, although ognized and reorganized species are provided. the nature of Malagasy environmental dynamics ' Associate Professor, Department of Anatomy, Duke University Medical Center, Durham, N.C. 27710. Copyright © American Museum of Natural History 1987 ISSN 0003-0082 / Price $4.75 2 AMERICAN MUSEUM NOVITATES NO. 2889 is not known in detail before about 10,000 BP, disjunctions in the species ranges ofMalagasy ver- and not at all before 35,000 BP. In any event, it tebrates occurred simultaneously about 2000 years is no longer necessary to believe that all known ago, when the island was first settled by humans. INTRODUCTION PRELIMINARIES TO THE REVISION The first concerns the ontogeny of tooth OF MICROGALE replacement in Microgale. Dobson (1882), Shrew tenrecs are sometimes considered to Forsyth Major (1897), and Leche (1907) be the most primitive members of Tenrec- pointed out long ago that some tenrecids erupt oidea (Eisenberg and Gould, 1970). They their molars before shedding any deciduous outwardly resemble other unspecialized so- teeth other than the third milk incisors. Un- ricomorph insectivores (e.g., Crocidura) in fortunately, this fact was frequently ignored possessing dense, rather velvety fur, abun- by later authors, who unwittingly distin- dant vibrissae, tiny eyes, short pentadactyl guishedjuvenile and adult morphs ofthe same limbs slung under a long, fusiform body, and species according to supposed differentia of an elongated skull tapering into a narrow ros- their "permanent" teeth.2 More than a third trum. Notably, like other tenrecs they retain ofthe nominal species in the genus are based ancient plesiomorphies that have been lost on holotypes having part or all of their milk in virtually all other eutherian lineages (in- dentitions still in place-a record, of sorts, in cluding true shrews), such as variable and insectivore systematics. The initial step in rather low body temperature and cloacae in satisfactorily revising Microgale therefore in- both sexes (Nichol, 1984). volves matching older and younger ontoge- According to current species lists (Corbet netic stages of the same species. and Hill, 1980; Honacki et al., 1982) and the The second reason for species splitting is relevant systematic literature, unrevised Mi- related to the first, but is less amenable to crogale (21 nominal species, as grouped here) ready solution unless large samples are avail- is the third most speciose genus in Insectiv- able. Leche (1907) noted that, in Microgale ora, exceeded in this regard only by Sorex and some other Tenrecidae, juveniles may (50+ spp.) and Crocidura (100+ spp.). This attain the body size of many adults before is a remarkably large number of forms for a replacing any deciduous teeth. However, the primitive island-bound insectivore genus, and problem is actually more complicated than implies that Microgale has undergone an im- that, because unquestionably subadult ani- pressive degree ofadaptive radiation in Mad- mals frequently exceed average adult values agascar. Appearances are somewhat mislead- for such measurements as head-and-body ing, however, because at least half of the length and greatest skull length. These ob- species of shrew tenrecs do not deserve rec- servations could be explained in either oftwo ognition, and even the good taxa corporately ways. One possibility is that cryptic species represent no more than three or four adaptive exist within Microgale, differing from one types or lines. another only in size (and, of course, in what- Why have so many species ofshrew tenrecs ever mechanisms are responsible for main- been distinguished? Apart from the ubiqui- taining species integrity and reproductive iso- tous problem of authors employing narrow lation). But since "larger" and "smaller" criteria to distinguish species that later prove 2 The same error has also been committed in tenrecine to be within the range of variation of taxa systematics: the holotype ofDasogalefontoynonti (Gran- already long known, there are two other rea- didier, 1929) is actually ajuvenile ofSetifer setosus. This sons for nomenclatural surplusage in Micro- fact was first recognized by Poduschka and Poduschka gale. Since these reasons profoundly affect (1982), and I deeply regret that I did not see their paper analysis of species limits within the genus, it on the systematic status of Dasogale prior to the pub- is important to set them out here. lication of mine on the same subject (MacPhee, 1987). 1 987 MAcPHEE: MICROGALE 3 morphs have been collected in exactly the C or c adult or deciduous canine same places, on the same days, by the same cbc centrobuccal cleft collectors, one would also have to infer that ds distostyle the ranges of these species entirely overlap- hld hypoconulid an ecological improbability if reproductive I or i adult or deciduous incisor iof infraorbital foramen isolation is really present, and reason enough L lower (any tooth) for decisively rejecting this argument. The lf lacrimal foramen alternative would be to infer that the growth M molar (followed by number of molar ac- curve in some species of Microgale is not as cording to conventional primitive eu- tightly controlled, genetically or hormonally, therian formula) as it is in most eutherians. Instead, there seems mf mental foramen to be an almost reptilian propensity for in- ms mesiostyle dividual size to vary significantly within and P or p adult or deciduous premolar (followed across age classes, perhaps in relation to nu- by number of premolar, according to trition or some other limiting factor. No lon- conventional primitive eutherian for- mula and assuming loss of P/p 1) gitudinal studies ofgrowth in Microgale have pa paracone been published, although the regulation of pac posterior accessory cusp (= hypoconu- size in Tenrecidae should be an attractive lid) problem in comparative physiology (see, pad paraconid (= anterior accessory cusp) however, Eisenberg and Maliniak [1974] for pbc posterior buccal cleft ontogenetic changes in single individuals of pe posterior ectostyle M. dobsoni and talazaci). For this study, high prd protoconid variance in metric traits complicates the def- tpm zygomatic process of maxilla inition of species boundaries. U upper (any tooth) ABBREVIATIONS AND MEASUREMENTS Measurements and abbreviations used in Institutional abbreviations tables and graphs AMNH Department of Mammalogy, Ameri- EL ear length can Museum ofNatural History, New GSkL greatest skull length York H holotype BMNH Department of Zoology (Mammals), HBL head and body length British Museum of Natural History, HFL hind foot length, from calx (heel pro- London cess) of calcaneus to claw tip of long- FMNH Department ofZoology, Field Museum est digit of Natural History, Chicago ICW width of anterior portion of rostrum, MNHN Laboratoire de Zoologie (Oiseaux et above canines Mammiferes), Museum National IMW distance between buccal surfaces of up- d'Histoire Naturelle, Paris per third molars MCZ Department of Mammals, Museum of L lectotype Comparative Zoology, Harvard MdL length of mandible, from angular pro- University cess to alveolus of lower first incisor UM Service de MUTL maximum upper toothrow length, distal Paleontologie, Universite de aspect of upper third molar to labial Madagascar, Antananarivo aspect of upper first incisor USNM Division of Mammals, United States P paratype National Museum TL