Mammalian Biology Zeitschrift fuÈr SaÈ ugetierkunde

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Original investigation A new species of murid (genus Mayermys) from south-eastern New Guinea

By K. M. HELGEN School of Earth and Environmental Sciences, University of Adelaide, and South Australian Museum, North Terrace, Adelaide, Australia

Receipt of Ms. 09. 12. 2003 Acceptance of Ms. 17. 02. 2004

Abstract

Mayermys is the only muroid genus with a single molar in each quadrant of the jaw. This distinctive genus is restricted to montane New Guinea and has previously been considered monotypic. Here a second species of Mayermys is described from the mountains of far south-eastern Papua New Gui- nea. The dentition of this new species is more reduced than that of any other species of rodent, liv- ing or fossil.

Key words: , , Papua New Guinea,

Introduction

On the basis of data derived from studies of 1804, Parahydromys Poche, 1906, Cross- skulls and teeth, reproductive systems, and omys Thomas, 1907, Microhydromys Tate immunological distances, the amphibious and Archbold, 1941, Tate water-rats and small-bodied shrew-rats of and Archbold, 1941, Xeromys Thomas, New Guinea and Australia are generally 1889, Thomas, 1897, Pseudohydro- thought to comprise a monophyletic group mys RuÈ mmler, 1934, Neohydromys Laurie, (Tate 1951; Laurie and Hill 1954; Lidick- 1952, and Mayermys Laurie and Hill, 1954 er 1968; Menzies and Dennis 1979; Mus- (Watts et al. 1992; Breed 1997;reviewed ser and Heaney 1992; Watts and Baver- by Musser and Carleton 2004) (however, stock 1994; Flannery 1995; Breed and both the integrity of this large grouping Aplin 1995) characterized by, among other and the boundaries and interrelationships traits, basin-shaped molars and/or reduced of certain genera remain to be firmly estab- 3 or absent third molars (M /3). This group, lished;see Musser and Carleton 2004). Of often classified as the murid subfamily Hy- these genera, one of the most phenetically dromyinae or (now more commonly) the distinctive is Mayermys, diagnosed by pos- murine tribe Hydromyini (Watts and Ba- session of only a single molar in each quad- verstock 1994; Flannery 1995) includes rant of the jaw (i. e. with only eight teeth in the murid genera E. Geoffroy, total ± four incisors and four molars, fewer

1616-5047/05/70/01-061 $ 30.00/0. Mamm. biol. 70 (2005) 1 ´ 61±67 62 K. M. HELGEN than any other rodent). Until now Mayer- Distribution: M. germani is known only mys has been considered a monotypic from the type locality (Fig. 1) at approxi- genus, with the single species M. ellermani mately 1 300 m. The holotype is the only Laurie and Hill, 1954 (Laurie and Hill specimen of the genus Mayermys collected 1954; Menzies and Dennis 1979; Flannery from the south-eastern peninsula of New 1995; Musser and Carleton 2004). A sec- Guinea. ond, morphologically distinctive species is Its sister species, M. ellermani, is recorded described here, based upon a newly-ob- throughout the Central Cordillera of New tained specimen of Mayermys from far Guinea from the Snow Mountains (in Pa- south-eastern New Guinea. pua Province, ) to the vicinity of Wau (in Morobe Province, Papua New Gui- nea), at elevations between 1 400 and Material and methods 2 800 m (Fig. 1, Tab. 2). Etymology: The specific epithet honours Specimens discussed here are deposited in the Pavel German, collector of the holotype collections of the Australian Museum, Sydney (AM);the American Museum of Natural History, New York (AMNH);the Bernice P. Bishop Mu- seum, Honolulu (BBM);the Natural History Mu- Table 1. Selected measurements for Mayermys eller- seum, London (BMNH);and the Museum of Ver- mani and the holotype of M. germani. Values are means tebrate Zoology, Berkeley, California (MVZ). ± SD, with ranges below, with sample size in paren- Craniodental variables were measured with digi- theses. tal callipers to the nearest 0.01 mm;external vari- ables were recorded by the original collector in M. ellermani M. germani the field. Linear measurements are given in milli- metres, weights in grams. Weight 17.6 ± 2.93 29.5 13±21.3 (16) Head-body length 96.2 ± 5.39 105 Results 88.5±103 (23) Tail length 102.3 ± 5.47 103 Mayermys germani new species 90±113 (23) Holotype: The holotype of germani is Hindfoot length 21.6 ± 1.03 21 19±23 (23) AM M29245, adult male, skull and study skin, from Munimun Village (09°53' S, Ear length 10.9 ± 1.08 12.6 149°23' E), 1 300 m, near Agaun (Milne 7±12 (23) Bay Province, Papua New Guinea), col- Condylobasal length 23.3 ± 1.23 25.5 lected 11 August 1992 by P. German (field 21.7±24.9 (9) number FR341). The holotype ± an adult Zygomatic breadth 10.8 ± 0.18 11.7 male with large testes, snap-trapped on the 10.6±11.1 (9) ground ± is the only known specimen. Interorbital breadth 4.2 ± 0.22 4.9 Diagnosis: A rat with only one molar 3.9±4.6 (10) 1 1 (M /1) in each quadrant of the jaw (a trait M length 0.93 ± 0.13 0.68 shared only with Mayermys ellermani); 0.80±1.10 (11) body and cranial size larger than M. eller- M1 width 0.58 ± 0.05 0.44 mani (Tab. 1);ear dark grey (vs. pale grey 0.50±0.66 (11) in M. ellermani);tail sparsely haired, with M1 length 0.83 ± 0.15 0.61 very short hairs (more heavily haired, with 0.66±1.13 (7) longer hairs in M. ellermani);molars mark- M1 width 0.56 ± 0.05 0.44 edly reduced relative to M. ellermani 0.47±0.60 (7) (Fig. 4), upper incisors proodont but less Mandible length 12.9 ± 0.39 13.7 strongly procumbent than in M. ellermani 12.3±13.7 (9) (Fig. 3). Anew species of murid rodent (genus Mayermys) from south-eastern New Guinea 63

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Fig. 1. Distribution of Mayermys ellermani (filled dots; Central Cordillera) and M. germani (filled triangle; SE New Guinea).

Table 2. Comprehensive list of vouchered collection localities (and elevations) for Mayermys ellermani.

Morobe Province, Papua New Guinea Edie Creek (7°21' S, 146°40' E), 7 000 ft [= 2 135 m] (MVZ 129794±129796, 129798) Summit of Mt. Kaindi (7°21' S, 146°41' E), 2 255±2 350 m (AM M14399, PNGM 24661) Wau (7°20' S, 146°43' E), no altitude (PNGM 24667) Mt. Missim (7°13' S, 146°49' E), 1 980 m (BBM-NG 160959, 161196) Eastern Highlands Province, Papua New Guinea Purosa (6°40' S, 145°34' E), Okapa area, 1 970 m (AMNH 191424) Mt. Erimbari (6°12' S, 145°10' E), no altitude recorded (AM M24312) Chimbu Province, Papua New Guinea Mt. Wilhelm (5°49' S, 144°57' E): N slopes, 8 000 ft [= 2 440 m] (BMNH 53.277); Pengagl Creek, altitude uncertain (AMNH 191423) E face of lower Mt. Karimui (6°35' S, 144°49' E), 1550 m (AM M14827, 15324)

Western Highlands Province, Papua New Guinea Welya (5°41' S, 144°08' E), 8 000±9 000 ft [2 440±2 745 m] (BMNH 53.278, 53.279) Southern Highlands Province N slopes Mt. Giluwe (6°06' S, 143°18' E), 8 000±9 000 ft [2 440±2 745 m] (BMNH 53.280), 2 800 m (BBM-NG 91734) NNW slopes Mt. Bosavi (6°33' S, 142°50' E), 2 100 m (BBM-NG 103485) West Sepik (Sandaun) Province, Papua New Guinea 5 km S Bafunmin (ca. 5°06' S, 141°26' E), 1 600±2 300 m (BBM-NG 107905, 108176) Feramin (5°11' S, 141°38' E), 5 miles SE Telefomin, 1 400 m (BBM-NG 100357) Papua Province, Indonesia Porokma (4°00' S, 138°43' E), Lake Habbema area, 2 800 m (AM M26984, 26987) 64 K. M. HELGEN and of many other important spe- type of M. germani is 38% heavier than cimens from throughout the Melanesian re- AM M15324, the heaviest known specimen gion. of M. ellermani), chunkier (Fig. 2), and has Description: The morphology of this new a longer ear (Tab. 1). The tail is much less species agrees in most aspects with M. eller- hairy than that of M. ellermani, with tail mani as described by Laurie and Hill hairs more sparsely distributed and each (1954), Lidicker and Ziegler (1968), and hair less than or subequal to the length of Musser and Heaney (1992), but differs each tail scale ring (longer than the scale strikingly in the following traits. The pelage rings in M. ellermani) ± a striking difference is soft, dense, and dark smoky-grey above, between the two species. There are 17±18 and slightly lighter grey on the shoulders rings per cm in the mid-section of the tail, and venter (which is uniformly coloured, in agreement with the 15±18 reported for lacking a white chest flash), as in M. ellerma- M. ellermani (Laurie and Hill 1954; Li- ni. However, the ear is dark grey in M. ger- dicker and Ziegler 1968). mani, whereas it is flesh-coloured and con- The skulls of both species of Mayermys trasts with colouration of the dorsum in agree in general conformation and profile M. ellermani (see photographs in Flannery (Fig. 3). Both species have an elongate 1995 and Nowak 1999). The dorsal surfaces braincase that is distinctly constricted later- of the manus and pes are white (generally ally posterior to the squamosal roots of the pale greyish-white in M. ellermani), and the zygoma, and similarly tiny, rounded, dou- dorsal pelage of the rump is flecked with ble-rooted molars ± two derived traits ab- white. The tail is not irregularly mottled sent in other New Guinean shrew-mice, and has a conspicuous cream-coloured tail- including the closely-related genera Pseu- tip (21.5 mm long on the dry skin) more dohydromys and Neohydromys. The skull prominent than in most specimens of M. el- of M. germani is larger (and more robust in lermani. Dimensions of tail and hindfoot essentially all aspects) than that of M. eller- are similar in M. germani and M. ellermani, mani, the rostrum is not so dorso-ventrally but M. germani is larger-bodied (the holo- tapered as in that species (Fig. 3), and there

Fig. 2. Study skins of Mayermys ellermani (below, AM M26987, adult male, Lake Habbema area) and M. germani (above, AM M29245, adult male, Agaun area). Anew species of murid rodent (genus Mayermys) from south-eastern New Guinea 65

Discussion

Little can yet be said of this new species' basic biology, as it is thus far known by a single specimen. Its sister species, M. eller- mani, also little-known, is primarily an in- habitant of high-elevation moss forest (Li- dicker and Ziegler 1968; Flannery 1995) and is omnivorous ± taking insects, plant material, and fungi (Jackson and Woolley 1993). The single specimen of M. germani was collected at a lower elevation (about 1 300 m) than the altitudinal range of M. el- lermani as documented by museum speci- mens (1 400±2 800 m;16 trapping localities ± see Tab. 2). Throughout much of the Tertiary, south- eastern New Guinea was an island sepa- rated from the rest of New Guinea (Dow 1977; Flannery 1995). Relative to other parts of the modern-day island, the south- eastern peninsula of New Guinea thus has a partially independent geological and fau- nal history, and today the mountain ranges of south-eastern New Guinea (especially the far south-east) are a notable centre of Fig. 3. Skulls of Mayermys ellermani (above, AM mammalian endemism. In addition to M15324, adult male, Mt. Karimui, 1 550 m) and M. ger- Mayermys germani, species en- mani (below, AM M29245, adult male, Agaun area). demic to these south-eastern mountains in- clude the dasyure Murexia (Paramurexia) are striking dental differences between the rothschildi Tate, 1938, the bandicoot Micro- species. In particular, in M. germani the sol- peroryctes papuensis (Laurie, 1952), the itary molars are absolutely and relatively tree-mouse Chiruromys lamia (Thomas, smaller than in M. ellermani;the trend to- 1897), and the soft-furred rat Rattus van- ward dental simplification seen in hydro- deuseni Taylor and Calaby, 1983 (Flannery myin (Misonne 1969) thus reaches 1995; Va n Dyc k 2002), as well as unde- its greatest development in M. germani. scribed species of the marsupial genus Pha- Additionally, the upper incisors of M. ger- langer Storr, 1780 (Flannery, pers. comm.) mani, though proodont, are not so distinc- and the murine genera Menzies, tively procumbent as in series of M. eller- 1990 and Leptomys (Musser and Lunde, in mani (Fig. 3);the latter species shares this litt.). Additional montane endemics in the trait with Neohydromys fuscus Laurie, 1952 south-east include distinctive subspecies of and Thomas, 1889. The echidna (Zaglossus bartoni smeenki Flan- mandible is not as gracile as in M. ellermani nery and Groves, 1998), tree kangaroo (Fig. 3), and the lower incisors are long and (Dendrolagus dorianus dorianus Ramsay, considerably more upcurved, more like 1883), and ringtail possum (Pseudochirulus shrew-mice of the genera forbesi forbesi [Thomas, 1887]) (Flannery or Neohydromys (cf. photographs in Laurie 1995; Flannery and Groves 1998). Several and Hill 1954) than M. ellermani. Upper additional mammal taxa, including Peror- and lower incisors are ungrooved, as in yctes broadbenti (Ramsay, 1879), Spilocus- M. ellermani. cus maculatus goldiei (Ramsay, 1876), Dor- 66 K. M. HELGEN

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o 046 i 04 #*# 07* oo# 0* io# iw i* length M, Fig. 4. Dimensions of the upper and lower molars in M. ellermani (e) and M. germani (g). copsis luctuosa luctuosa (D'Albertis, 1874), bord, and Daphne Hills (BMNH), Carla Kishi- and Chiruromys forbesi forbesi Thomas, nami, Allen Allison, Fred Kraus, and Neal 1888, are also distinctive south-eastern Evenhuis (BBM), Darrin Lunde (AMNH), and New Guinean endemics, but are restricted Jim Patton and Christopher Conroy (MVZ). I thank Guy Musser for an insightful review of this to lowland habitats (such as lowland forests study, Tim Flannery, Don Wilson, and Steve Ri- and grasslands), rather than montane for- chards for ongoing assistance and advice, Pavel ests. German for important discussions, and Lauren Johnston for producing the map. My research has been supported by fellowships and grants Acknowledgements from the Australian-American Fulbright Commis- sion, the National Science Foundation (Graduate For access to specimens and other assistance dur- Research Fellowship), the Smithsonian Institution ing museum visits, I thank Sandy Ingleby and (Short-Term Visitor Program), and the South Tish Ennis (AM), Paula Jenkins, Richard Har- Australian Museum. Anew species of murid rodent (genus Mayermys) from south-eastern New Guinea 67

Zusammenfassung

Eine neue Muriden-Art (Gattung Mayermys) aus dem SuÈdosten von Neuguinea Mayermys ist die einzige Nagetier-Gattung mit nur einem einzigen Molaren in jedem Kieferast. Diese markante Gattung ist auf Gebirge in Neuguinea beschraÈnkt und gilt bisher als monotypisch. Hier wird eine zweite Art von Mayermys aus dem aÈuûersten SuÈdosten der Insel beschrieben. Die Be- zahnung dieser neuen Art ist staÈrker reduziert als die irgendeiner anderen lebenden oder fossilen Nagetier-Art.

References

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