AMERICAN MUSEUM

Novitates

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2730, pp. 1-23, figs. 1-1 3, tables 1, 2 June 7, 1982

Results of the Archbold Expeditions. No. 107. A New Genus of Arboreal Rat from Luzon Island in the Philippines

GUY G. MUSSER'

ABSTRACT The taxon latidens Sanborn, 1952 originally nar-like occlusal surfaces are not characteristic of named and described as a species ofRattus is taken Rattus. The species is known by two specimens out of that genus and placed in Abditomys, new from the island of Luzon in the Philippines. The genus. Some of its distinctive features, such as relationship oflatidens to other with nails nails instead of claws on the halluces, wide upper on the halluces is discussed. Aspects ofits natural incisors, and large molars with simple and lami- history are presented.

INTRODUCTION I propose a new genus for a native Phil- the fauna will be analyzed in a separate re- ippine rat originally described as Rattus la- port. tidens (Sanborn, 1952), endemic to the island There is an impression among - of Luzon in the Philippines. This report is ogists and biogeographers that the native one of several already published (Musser, Philippine rats are well known, especially 1977a, 1977b, 1979, 1981a; Musser and that spectacular segment of the fauna that Freeman, 1981; Musser and Gordon, 1981) lives on the western highlands in northern or in manuscript dealing with the Luzon (Thomas, 1898). This is not so. We and geographic distribution of Philippine know less about the Philippine rats than most murids. With this and future papers, I intend other murid groups in the Far East. The nat- to document the morphological limits ofcer- ural history of nearly all the native species tain species and provide information about is either unknown or encapsulated in sketchy their insular distributions and natural his- descriptions made by collectors. Many of the tories. Possible phylogenetic relationships of native genera were thought to be restricted

I Archbold Curator, Department of Mammalogy, American Museum of Natural History.

Copyright ©) American Museum of Natural History 1982 ISSN 0003-0082 / Price $1.90 2 AMERICAN MUSEUM NOVITATES NO. 2730

for their work with the Scanning Electron 1 bis Microscope and the resulting micrographs. a-lab Mrs. Frances A. Hufty, of Archbold Expe- alc ditions, Inc., contributed part ofthe financial pd- support for my work.

plc hd- ABBREVIATIONS AND METHODS a-lab- Specimens referred to here are in collec- pd- tions of the American Museum of Natu- plc- 7- al History, New York (AMNH); the Brit- hd- ish Museum (Natural History), London -lab- (BMNH); the Field Museum of Natural His- Pd- tory, Chicago (FMNH); the Rijksmuseum hd- van Natuurlijke Historie, Leiden (RMNH); and the National Museum ofNatural History FIG. 1. Nomenclature of dental structures us- of the Smithsonian Institution, Washington, ing right upper and lower molars of Lenothrix D.C. (USNM). canus. Upper molars: cusps are numbered accord- Values for lengths of head and body, tail, ing to Miller's (1912) scheme and are referred to hind foot, and ear are from the labels attached in the text with the prefix t; pc, posterior cingulum. to study skins. Cranial and dental measure- Lower molars: a-cen, anterocentral cusp; a-lab, ments were taken with dial calipers graduated anterolabial cusp; a-ling, anterolingual cusp; pd, to tenths of millimeters; limits ofthose mea- protoconid; hd, hypoconid; md, metaconid; ed, surements are explained in Musser (1970, entoconid; pc, posterior cingulum; alc, anterior 1979). The nomenclature I use for cusps and labial cusplet; plc, posterior labial cusplet. cusplets on the molars is diagrammed in fig- ure 1. DIAGNOSIS AND DESCRIPTION to Luzon or Mindanao but actually have more extensive distributions over the archi- Named and described by Sanborn (1952) pelago. The diversity ofthe fauna, at the level as a species of Rattus, the characteristics of ofgenera and species, is greater than generally latidens are known from an adult female (the realized. There are specimens hidden under holotype) and an adult male, both from the misidentifications in museum collections island of Luzon in the Philippines. Sanborn that represent new taxa, there are samples of (1952, p. 125) diagnosed latidens as "A large new species obtained from various islands dark species with tail slightly longer than during recent exploration, and there are head and body; skull short, with thick ros- many species now placed in Rattus that really trum, large bullae and short palate ending do not belong there. The species, latidens, is between last molars; molar pattern like that one of these. To separate it from Rattus, to of Rattus, but incisors nearly twice the width contrast it to other species that have nails found in most species of Rattus and wider instead ofclaws on their halluces, and to pro- than in the largest species." Those wide in- vide notes and speculations about its natural cisors should have prompted Sanbom to look history are my intentions here. closer at the holotype. The configuration of I am grateful to the curators who allowed the cranium and the occlusal patterns of the me access to collections under their care; to molars are unlike species of Rattus; further- Ms. Fran Stiles, Ms. Marjorie Shepatin, and more, each hallux has a nail instead ofa claw, Mr. Helmut Sommer for the artwork; to a specialization not found in any Rattus. The Messrs. Arthur Singer, Peter Goldberg, and two specimens of latidens represent a species Jim Coxe for the photographs; and to Mr. outside of the morphological radiation char- Robert J. Koestler and Mr. Richard Sheryll acterizing not only Rattus but all other known 1982 MUSSER: LUZON ISLAND RAT 3 genera of murids and requires its own genus, first lower molars four-rooted; each third up- which is named and diagnosed below. per molar squarish in occlusal outline, only a little smaller than the second; upper molars with simple occlusal surfaces, no cusps t7, no ABDITOMYS, NEW GENUS posterior cingula, no cusps t3 on second and TYPE SPECIES: Rattus latidens Sanbom third molars; cusp t9 broadly merged with (1952, p. 125); based on the holotype, an cusp t8 on first and second molars; front two adult female (FMNH 62347), collected April rows of cusps form thin and gently arcuate 29, 1946, from Mount Data, 7500 feet, laminae on each first upper molar and on the Mountain Province, Luzon, the Philippines. front row of each second and third upper An adult male (USNM 357244) obtained on molar; last row ofcusps on each upper molar March 14, 1967 from Los Baflos, Laguna laminar, nearly transverse; occlusal surfaces Province, Luzon (Barbehenn, Sumangil, and of lower molars consisting of transverse Libay, 1972-1973) is the only other known laminae formed from two elongate cusps; specimen of the species. posterior cingulum a wide flat-topped cone KNowN DISTRIBUTION: The island of Lu- in center ofposterior margin on first and sec- zon in the Philippine Islands (fig. 2). ond lower molars; small anterolabial cusps ETYMOLOGY: Abditomys is formed by com- on second and third molars; no anterocentral bining the Latin, abditus, meaning hidden or cusp at front of first lower molar; no labial concealed, with the Greek, mys, for mouse cusplets on any lower molars. or rat. I allude to the past concealment of DESCRIPTION: Abditomys latidens is a large- latidens-so distinctive in features of skin, bodied rat with a tail longer than the com- skull, and teeth-within the morphological bined lengths of head and body (table 1, fig. confines of the genus Rattus, to which it is 3). The upperparts of the head and body are not closely related. brown with tawny highlights. The underparts DIAGNOSIS: A genus ofarboreal murid dis- are buffy yellow with gray suffused through tinguished from all other species by the fol- the base of the coat. Color of the venter is lowing combination of features: large body indistinctly demarcated from that ofthe dor- size, long, monocolored tail; four pairs of sum. The pelage covering the head and body mammae; a large nail instead of a claw on is long (30-35 mm. over the back) and coarse, each hallux; squamosal roots of the zygo- but not spinous. Long (up to 50 mm.) and matic arches situated high on sides of the conspicuous guard hairs emerge from the braincase; squarish interparietal, its anterior coat everywhere over the top and sick.s Z-f the one-third between the parietals, the posterior body, and are especially prominent over the two-thirds roofing the occipital bulge; no rump. The ears are large and brown. The tail strut ofalisphenoid bone covering lateral part is brown everywhere, appears naked, but is of the alisphenoid canal; masticatory-bucci- covered with short, stiff, inconspicuous hairs. nator foramina merged with foramen ovale The feet are dark or pale brown over the en- accessorius; incisive foramina long and thin; tire dorsal surfaces down to the base of the palatal bridge short, ending well before backs claws. The claws on the front feet are sharp of third molars; deep mesopterygoid and and small, especially relative to the large dig- pterygoid fossae; sphenopalatine and sphe- ital pads all textured with transverse and nopterygoid vacuities large; bullae large and semicircular striations. There is a prominent inflated; upper incisors very wide, absolutely pointed nail on each hallux; the other digits and relative to breadth of rostrum; molars in claws long and wide, gleaming white, the uppers terminate large, elongate, sharp (fig. large relative to area of palatal bridge; high 4). The female has four pairs of mammae: a cusps that slant back with appreciable over- pectoral pair, postaxillary pair, and two in- lap between first and second molars, and be- guinal pairs. The male (testes were abdomi- tween second and third, especially in the up- nal) has a prominent midventral cutaneous per molars; first upper molars five-rooted, glandular area, 70 mm. long and 6 mm. 4 AMERICAN MUSEUM NOVITATES NO. 2730

LI 0-1500 ft. EZ 1500 - 5000 ft. E 5000 - 8000 ft. E 8000 + ft.

.

. *0

;. C%@:-

' .

0

FIG. 2. Map of Luzon Island in the Philippines. Specimens of Abditomys latidens are from Mount Data and Los Bafios. 1982 MUSSER: LUZON ISLAND RAT 5

TABLE 1 Measurements (in Millimeters) of Adult Abdito- latidens from Luzon Island in the w mys Philippines FMNH USNM 62347a 357244 Measurement female male Length of head and body 232 216 Length of tail 242 271 Scale rows/cm on tail 7 9 Length of hind foot 45 47 Length of ear 21 24 Weight (g) - 269 i. Greatest length of skull 50.6 49.5 A. Zygomatic breadth 25.9 24.2 .t Interorbital breadth 6.0 5.7 of nasals .*. Length 19.4 18.9 4 ,- Length of rostrum 16.6 15.3 Breadth of rostrum 9.6 8.6 Breadth of braincase 18.7 18.0 '-: .v Height of braincase 14.1 13.5 *.t. Breadth of incisor tips 5.4 3.9 O., Breadth of zygomatic plate 6.0 5.4 Depth of zygomatic notch 3.1 3.1 Length of diastema 13.4 13.0 Palatilar length 22.5 22.1 I Palatal length 26.3 25.3 Postpalatal length 19.4 18.3 Length of incisive foramina 9.0 9.3 Breadth of incisive foramina 2.9 2.8 Length of palatal bridge 9.2 9.1 Breadth of bridge at M' 3.4 3.4 I Breadth of bridge at M3 4.7 3.9 Breadth of mesopterygoid fossa 2.7 3.1 Length of bulla 9.0 9.5 Height of bulla 7.8 8.2 Alveolar length of M'-3 9.7 9.9 Breadth of M' 3.4 3.1 Breadth of M2 3.5 3.0 Breadth of M3 2.6 2.6 Actual length of M,_3 10.4 9.8 Breadth of Ml 2.9 2.9 Breadth of M2 3.2 3.0 Breadth of M3 3.0 2.8 FIG. 3. Abditomys latidens. Dorsal and ventral a Holotype. views ofUSNM 357244, the adult male from Los Bafios. Its measurements are listed in table 1. Strong and nearly parallel zygomatic arches, across its widest place (partially seen in fig. together with a short and broad rostrum and 3). squarish braincase provide the rectangular The cranium of A. latidens is large, high, appearance. Nasals, which are narrow proxi- stocky, and roughly rectangular from a dorsal mally but expand to become wide distally, view (table 1, fig. 5; Sanborn, 1952, fig. 10). enhance the broadness ofa squarish rostrum. 6 AMERICAN MUSEUM NOVITATES NO. 2730

IN --!- 'N -'ov <. - I -- O.ViWAF,--

FIG. 4. The hind foot of Abditomys latidens. Drawn from USNM 357244. Note the nail on the hallux.

The nasals are nearly flat for about three- opening where the contents ofthe canal enter fourths of their lengths, which gives the ros- the sphenoidal fissure (fig. 7A). When a strut trum a broad, flat dorsal surface. The inter- of alisphenoid bone is present, it separates orbital region is pinched in, narrower than the masticatory-buccinator foramina, ante- the rostral breadth. High, thick ridges define rior to the strut, from the foramen ovale ac- the dorsolateral margins of the interorbital cessorius, posterior to the strut (as in Cra- region and extend back along the postorbital teromys, for example; see Musser and area to the dorsolateral margins ofthe brain- Gordon, 1981). With the strut ofbone miss- case where they become reduced in size and ing, the masticatory-buccinator foramina prominence and nearly disappear near the have merged with the foramen ovale acces- occiput. The interparietal is about as long as sorius and appear functionally absent. The it is wide; the front one-third is between the foramen ovale and opening of the alisphen- parietals, the posterior two-thirds forms the oid canal into the sphenoidal fissure are now top of the deep occipital region. High, thin seen where they would be hidden if a strut ridges mark the sides of the braincase where were present (fig. 7A). the occipital and squamosal bones join. The The inflated bullae, large absolutely and walls of the braincase above the squamosal relative to size of the cranium, are evident roots of the zygomatic arches slope toward in side view. Each bulla is separated from the the midline of the cranium. squamosal bone by a wide postglenoid va- In side view, the zygomatic plates are wide, cuity. Above each bulla, the squamosal bone appear robust, and their anterior borders is complete, not perforated or notched by a project well in front ofthe dorsal roots ofthe squamoso-mastoid vacuity that would sep- zygomatic arches. The squamosal roots ofthe arate the bone into a dorsal part and a ventral zygomatic arches are set high on the brain- tympanic hook (fig. 7A). case. In ventral view (fig. 5, fig. 7B), the incisive The configuration of each alisphenoid re- foramina are narrow, long, and slightly con- gion at the base of the braincase just above stricted posteriorly; their back margins pen- each pterygoid ridge is like that in Rattus etrate between the anterior margins of the (Musser, 1981a). A strutlike wall of alis- first molars by 0.5 mm. in FMNH 62347 and phenoid bone, present in many murids 0.4 mm. in USNM 357244. The palatal (Musser, 1981 a), is gone from the lateral side bridge is narrow, thick, scored by deep pal- of the alisphenoid canal, which is now an atine grooves, and short; its posterior edge open channel. Above the channel is a large is situated 1.0 mm. before the ends of the foramen ovale and anterior to that a small toothrows in FMNH and 0.8 mm. in USNM 1982 MUSSER: LUZON ISLAND RAT 7

a

b A.. * #~~~~~~~~~~~~.

c FIG. 6. Dentaries from the same specimens shown in figure 5: a, labial view of R. r. diardii; '-. b, labial view of A. latidens; c, lingual view of A. latidens. Approximately X1. IC, X I -t. sphenopalatine vacuities that extend to the back ofthe orbits (fig. 8). Each pterygoid fossa is deep, its floor slanted down toward the midline of the cranium and its anterior two- thirds perforated by a large sphenopterygoid .I vacuity. The posterolateral edge of the pter- ygoid platform behind each foramen ovale a b is a definite, high ridge. In ventral view the bullae are large and inflated; the eustachian tubes are short and inconspicuous. Shapes and positions of some foramina in each orbit are ofinterest. The sphenopalatine foramen is very large and conspicuous. It is set well anterior to the much smaller and a nearly hidden dorsal palatine foramen (fig. 8). The optic foramen is also large. It is sep- arated from the anterior end of the large and elongate sphenopalatine vacuity by a narrow bony strut. Each dentary is large and stocky (fig. 6). b That part of the ramus anterior to the tooth- row is short and deep. The coronoid FIG. 5. Views of adult crania: a, Abditomys process latidens (USNM 357244) is contrasted with b, an is large. A deep concavity forms the back example of Rattus rattus diardii from West Java margin of the dentary. The masseteric ridge (AMNH 250104). Approximately xl. is thick and prominent. On the inner side of the mandible, a shelf extends from the back 357244. The mesopterygoid fossa is deep and of the toothrow diagonally past the mandib- conspicuously narrower than the palatal ular foramen onto the bottom of the con- bridge; its walls are breached by spacious dyloid process. 8 AMERICAN MUSEUM NOVITATES NO. 2730

aIs'~ ~ ~ p

q

max ab

= trc *~~~~~

- >~~~~~~~~~bs~~~~~ptr--- mif ab ptb AL,.~~~~~~~~~~~~~~~~~'t,

FIG. 7. The back part of the cranium in Abditomys latidens (USNM 357244): A, lateral view; B, ventral view. Abbreviations: a, anterior opening ofthe alisphenoid, where it empties into the sphenoidal fissure; ab, auditory bulla; alc, alisphenoid canal, which is an open channel; als, alisphenoid bone; bo, basioccipital bone; bs, basisphenoid bone; et, bony eustachian tube; fo, foramen ovale; mas, mastoid portion ofthe petromastoid; max, maxillary bone; mlf, middle lacerate foramen; oc, occiput; pa, parietal bone; pgl, postglenoid vacuity; ps, presphenoid bone; pt, periotic portion of the petrosal; ptb, pterygoid bridge, which is a definite ridge; ptf, pterygoid fossa; ptr, pterygoid ridge; sf, sphenoidal fissure; spt, sphenopterygoid vacuity; sq, squamosal bone; srza, squamosal root of the zygomatic arch; sv, spheno- palatine vacuity; trc, transverse canal. Hill (1935), Wahlert (1974), and Musser (1981a) discuss the foramina and significance of some configurations. 1982 MUSSER: LUZON ISLAND RAT 9

fr

r IC

1.

I max

W ..- -W!, 9 .1 *.c .",, li.' ,WI I& ',

FIG. 8. The orbital and postorbital region in Abditomys latidens (USNM 357244). Abbreviations: dpl, dorsal palatine foramen; fr, frontal bone; max, maxillary bone; ml, first upper molar; op, optic foramen; spl, sphenopalatine foramen; sq, squamosal bone; sv, sphenopalatine vacuity. Note the slant to the high cusps and the way one molar overlaps another.

The incisors of A. latidens are large and third, which is squarish in occlusal outline, smooth, the enamel layers of the uppers are is only a little smaller than the second. The orange, those ofthe lowers yellowish orange. high cusps slant back so that the first molar The uppers emerge from the rostrum at a appreciably overlaps the front part ofthe sec- right angle (opisthodont) and are very wide ond and the second overlaps the third (figs. (56% ofthe rostral breadth in FMNH 62347 8 and 9). The occlusal surfaces of the uppers and 45% in USNM 357244). are simple in configuration: no cusp tlbis, Abditomys latidens has big, chunky hypo- t2bis, t7, accessory labial cusp behind cusp sodont molars that are ivory-colored, glisten, t6, or posterior cingulum occurs in any ofthe and without the brown or blackish tarry en- teeth; and cusp t3 is absent from the second crustations often found in other murids. Each and third molars. The cusps on all the teeth first upper molar is anchored by five roots form either gently arcuate rows-such as the (large anterior and posterior, two lingual, and first and second laminae on the first molar, a labial), the second by four roots, and the and the first lamina of the second and third third by three. Each first lower molar has four molars-or nearly transverse laminae, those roots (large anterior and posterior, small la- at the back of each tooth. Cusp tl on all bial, and small lingual), each second and third three teeth, and cusp t4 on each first and lower molar is anchored by three roots (two second molar are round and discrete-espe- small anterior and a large posterior). cially cusp t4 on the first molar, which is The upper molars form wide, prominent nearly separate from cusp t5 -but the labial rows in the bony palate. The second upper cusps are elongate and merged with the cen- molar is about as wide as the first, and the tral cusps to form most ofthe surface ofeach 10 AMERICAN MUSEUM NOVITATES NO. 2730

the labial margins of the first molars, and no posterior labial cusplets occur on either the second or third molars in the two specimens I examined. There is a small anterolabial cusp on each second and third molar. COMPARISONS WITH RATTUS +/ s I compare Abditomys latidens with Rattus because latidens was originally described as a species in that genus. The Asian forms of tA ^ vV R. rattus, R. r. diardii (Java) and R. r. flavi- pectus (China), are the examples I use; spec- imens of them are compared with that of A. latidens in figure 5 (crania), figure 6 (denta- ries), and figure 10 (molar rows). Abditomys 7)j latidens possesses the following characteris- tics that contrast with those of Rattus.

./ 1. A nail (or scalelike claw) is on each hal- lux. Every species of Rattus has claws on the "ql halluces. ;i4, 2. The dorsal surfaces of the nasals are i nearly flat for most of their lengths and only .1 gently convex near their tips. In Rattus, the nasals are not flat but rounded on top along J"/ their lengths. FIG. 9. Occlusal views of right molar rows of 3. Squamosal roots ofthe zygomatic arches Abditomys latidens (USNM 357244). M13 is on are set higher on sides of the braincase. the left, Ml3 on the right. See table 1 for mea- 4. The sides ofthe braincase slope outward surements. from the temporal ridges to the squamosal roots. In Rattus (certainly R. rattus), the sides of the braincase are vertical or nearly so. 5. The interparietal is narrow, the anterior lamina. Cusp t9, for example, is large but one-third sits between the parietals, the pos- poorly defined because it is broadly merged terior two-thirds roofs part of the occipital with cusp t8 on the first and second molars. region. Rattus has a short, wide interparietal The stocky lower molars also have high, that is farther posteriorly, forming nearly the slanting cusps, and are simple in occlusal to- entire roof of the occipital region. pography (fig. 9). There are three transverse 6. Each zygomatic plate is taller, joining rows of cusps (two in each row) on the first the dorsal root of the zygomatic arch nearly molar and two rows on each second and third at a level with the top of the cranium. The molar. The laminae are separated from each plate is relatively shorter in Rattus, meeting other and lean forward. A large and discrete the dorsal root of the zygomatic plate about posterior cingulum sits at the back of each one-third of the way down from the top of first and second molar, distinctly separate the cranium. from the lamina in front ofit. The first molar 7. The bullae are much more inflated and is oblong in occlusal outline, the second and appreciably larger relative to size of the cra- third squarish. The front lamina on each first nium. lower molar is formed ofa large anterolingual 8. The cranium is relatively deeper, espe- cusp and a smaller anterolabial cusp merged cially between the interorbital area and the to form a lamina distinctly set apart from the bony palate. one behind; there is no anterocentral cusp. 9. The palatal bridge sits well above the No anterior or posterior cusplets occur along floor ofthe basisphenoid (as seen from a ven- 1982 MUSSER: LUZON ISLAND RAT 11 tral view), is deeply scored by palatine 19. Occlusal surfaces of the lower molars grooves, is narrow, and ends anterior to the consist of wide, transverse laminae, each posterior margins of the toothrows. In Rat- composed of two elongate cusps. The lami- tus, the bridge is much lower relative to the nae are set apart from each other. The lam- basisphenoid, very wide, with either shallow inae are close together in Rattus, most are or faint palatine grooves, and projects beyond chevron-shaped rather than transverse. the posterior margins of the toothrows to 20. The front lamina of each first lower form a wide and long shelf. molar is slightly angled to the posterolateral 10. The mesopterygoid and pterygoid fos- side, distinctly separated from the lamina sae are relatively much deeper, a reflection behind, and consists ofdiscrete anterolingual of the raised bony palate. and anterolabial cusps set on about the same 11. The upper incisors are orthodont and axis. In Rattus, the front lamina is formed very wide, about half the width of the ros- of a large anterolingual cusp and a smaller trum. The uppers are either orthodont or op- anterolabial cusp set at nearly a right angle isthodont and much narrower, about a third to the other; the backs ofthe cusps are pressed the width of the rostrum (an average of 33% tightly against the anterior surface ofthe sec- of the rostral breadth in a series of 20 R. r. ond lamina. diardii from Java). 21. The lamina at the back of each third 12. The upper molars are big and chunky, lower molar is nearly as wide as the front the toothrows occupy about two-thirds ofthe lamina and transverse. In Rattus, the pos- bony palate. Rattus has small molars, the terior lamina is narrower relative to the one toothrows are short and narrow relative to in front, and slanted anterolabially. the wide and long expanse of bony palate. 22. Each posterior cingulum on the first 13. Each third upper molar is squarish and and second lower molars is round or slightly only a little smaller than the second. Each elliptical in cross-section and distinctly sep- third molar is round or oblong in Rattus and arated from the lamina in front of it. The much smaller than the second. posterior cingula are elliptical in Rattus and 14. Occlusal surfaces of the uppers consist set closer to the laminae, often merging with of wide and gently bowed laminae in which them at places. only some of the lingual cusps are still dis- 23. There are no anterior or posterior labial crete. The lamina at the back of each molar cusplets on the first lower molars, and no is transverse or nearly so, a configuration due posterior labial cusplets on the second mo- to an elongate cusp t9 merged on the same lars. There is an anterior labial cusplet on axis with an elongate cusp t8. The laminae each first molar in some examples of Rattus; in Rattus are arcuate and conspicuously cus- posterior labial cusplets occur on both the pidate. Cusp t9 on each first and second mo- first and second molars in most specimens. lar is discrete and directed anterolabially; those posterior laminae are not transverse. COMPARISONS WITH MURINES 15. No cusp t3 occurs on either the second NAILS or third upper molars. Cusp t3 is often pres- HAVING ent, although small, on the second and third In having nails on its halluces, Abditomys molars of Rattus. latidens is unique among rats native to the 16. Each dentary is more robust and Philippine Islands. The character is rare even higher; the portion anterior to the molar row within muroid and is found in only is relatively shorter and deeper. two groups. One consists of Dendromus, 17. The lower molars are large and chunky, Megadendromus, and Prionomys, which are especially relative to the dentary. Rattus has in the Dendromurinae, a small assemblage much smaller molars. of species native to Africa. 18. Each third lower molar is squarish in The other group is the Murinae. Among occlusal outline and nearly as large as the the hundreds of species in that group, only second molar. Each third molar is triangular the following seven genera and 14 species in outline in Rattus. have nails on halluces. 12 AMERICAN MUSEUM NOVITATES NO. 2730

p

4

f ".. I ' 1

I. 1. !,-- t-. x 1,p .I .s~~~~~~ I

sr _iwt~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1 i~'

FIG. 10. Occlusal views contrasting right molar rows of Abditomys and Rattus. A and D: MI-3 and M, 3, respectively of A. latidens (USNM 357244). B and C: M'-3 and M,-3, respectively of R. rattus flavipectus from China (AMNH 84677). Approximately x10.

1. : H. longicaudatus and H. de- the Malay Peninsula, Sumatra, and Java lacouri; the mainland of Southeast Asia (Ellerman, 1941). and the Malay Peninsula (Musser, 1972). 5. Chiromyscus: C. chiropus; Southeast Asia 2. Chiropodomys: C. gliroides, C. muroides, (Musser, 1981a). C. calamianensis, C. major, and C. karl- 6. Kadarsanomys: K. sodyi; Java (Musser, koopmani; Southeast Asia, the Sunda 1981c). Shelf, and the Mentawai Islands (Musser, 7. Abditomys: A. latidens; Luzon, the Phil- 1979). ippine Islands. 3. : V. oleracae and V. nolthenii; India, Ceylon, and Southeast Asia (- Because nails on halluces is a specialization ser, 1979). and one that occurs infrequently among mu- 4. Pithecheir: P. melanurus and P. parvus; roid rodents, especially among the Murinae, 1982 MUSSER: LUZON ISLAND RAT 13

TABLE 2 Distribution of Primitive (P) or Derived (+) Expressions of 26 Traits among 7 Genera of Murine Rodents Chiro- Hapalo- Vande- Chiro- Kadar- Abdito- podomys mys leuria Pithecheir myscus sanomys mys 1. Dorsolateral margins of braincase + + P + + + + 2. Sides of braincase + + P P + P P 3. Squamx.sal roots of zygomatic arches P + + + P + P 4. Alisphenoid complex + + P + P + + 5. Size of bulla P + P + P + + 6. Attachment of bulla + + + P P + + 7. Incisive foramina P P P P + + + 8. Mesopterygoid fossa P P + P P P + 9. Pterygoidfossa P P P P + + + 10. Pterygoid platform P + P + P + + 11. Roots of M' P P P P P + + 12. Roots of M, P P P P + + + 13. Height of cusps P P P P P P + 14. Sizeofmolars P P P P + P P 15. Overlap of molars P P P + + + + 16. Cuspstlbisandt2bis P + P + P P P 17. Cuspt7 + + + + P P P 18. Posterior cingulum P + P P + P + 19. Cuspt9 P P P P + P + 20. Cuspt., P P P P + P + 21. Unionofcusps P P P P + P + 22. Anterolabial and anterolingual cusps P P P P + P P 23. Anterolabial cusp P P P P + P P 24. Fifth digit P P + P P P P 25. Lamina P P P P P P + 26. Rows of cusps P + P P P P P Total derivedtraits 5 11 5 8 13 11 17 a Numbers correspond to numbered descriptions ofthe traits in the text. See Musser (198 la) for more information about some of the features.

I studied. species in the seven genera listed 1. Dorsolateral margins ofbraincase: Slight above to determine if they were closely re- beading al(ong dorsolateral margins ofthe in- lated because they shared this derived trait. terorbital aand postorbital regions; the brain- Elsewhere (Musser, 1981a), I presented hy- case is eith er smooth all over or has low bead- potheses ofderived and primitive conditions ing along the dorsolateral margins of the in 29 external, cranial, and dental features of anterior hailfand is smooth over the posterior several genera from the Indo-Australian re- half. (Medilium to high ridges or shelves out- gion that were once part of Rattus to note line the iInterorbital area and sweep back their possible phylogenetic relationships rel- along the (dorsolateral margins of the brain- ative to Rattus. I examined 23 of those same case, all tthe way to the occiput in some characteristics, as well as three new ones, in species.) the seven genera. These traits are briefly pre- 2. Sides ofbraincase: Sides ofthe braincase sented below: the primitive condition is de- slope outwiard from the dorsolateral margins scribed first, followed by the derivation in ofthe cranium to the squamosal roots of the parentheses. Distributions of the primitive zygomatic arches. (The sides are vertical or or derived states in the 26 traits are listed in nearly so.) table 2. 3. Squaimosal roots of zygomatic arches: 14 AMERICAN MUSEUM NOVITATES NO. 2730

The roots originate high on the upper half of 11. Roots of first upper molars: Each first the braincase, often close to the temporal upper molar is three-rooted (anterior, lingual, ridges and well above the bullae. (The roots and posterior) or four-rooted (a labial root are set halfway down the braincase or lower, in addition to the three primary roots or a just above the bullae.) divided lingual root along with only an an- 4. Alisphenoid complex: A strut of ali- terior and posterior root). (Each first upper sphenoid bone covers the lateral part of the molar is five-rooted -anterior, posterior, two alisphenoid canal and separates the foramen lingual, and one labial.) ovale accessorius from the masticatory-buc- 12. Roots of first lower molars: Each first cinator foramina. (The strut is gone, the ali- lower molar is two-rooted (an anterior and sphenoid canal is an open channel and the posterior root) or three-rooted (either a labial foramina have merged-they appear to be or a lingual rootlet in addition to the two functionally absent.) primary roots). (Each lower molar is four- 5. Size ofbullae: The bullae are moderately rooted-anterior, posterior, labial, and lin- to very small relative to size of the cranium. gual.) (The bullae are large relative to cranial size, 13. Height of cusps: The molars have low sometimes highly inflated.) to moderately high cusps, but definitely 6. Attachment of bullae: Each bulla is brachyodont. (The molars have high cusps, tightly attached to the squamosal bone. The clearly hypsodont.) postglenoid vacuity is small and usually con- 14. Size ofmolars: The upper molars grad- fined to the top ofthe bulla between the peri- ually decrease in size from the first to the otic and squamosal. (A wide, spacious va- third. (Each second upper molar is smaller cuity separates the dorsal and anterior margins than the first, but the third is reduced in size ofthe periotic and bulla from the squamosal.) and much smaller relative to the second.) 7. Incisive foramina: The incisive foram- 15. Overlap ofmolars: Cusps on the upper ina are short, their posterior edges terminat- molars are only slightly slanted and there is ing well anterior to the maxillary molar rows. little or no overlap among the three teeth in (The foramina are long, the posterior margins a toothrow, each essentially abutting against ending at the fronts of the first upper molars the other. (The cusps slant conspicuously or beyond them.) back, so that the first molar overlaps the sec- 8. Mesopterygoid fossa: The fossa is nearly ond, and the second overlaps the third.) as wide as the back part ofthe palatal bridge. 16. Cusps tlbis and t2bis: These cusps do Its walls are breached by thin, short spheno- not occur on the first and second upper mo- palatine vacuities or slits. (The fossa is one- lars of most specimens. (Either tlbis, t2bis, third to one-half the width of the palatal or both are present on first upper molars in bridge. The sphenopalatine vacuities are most specimens, sometimes the second mo- huge so that the presphenoid and anterior lars.) part of the basisphenoid appear suspended 17. Cusp t7: No cusp t7 is on any of the in air.) upper molars. (A cusp t7 occurs on the first 9. Pterygoid fossae: Each fossa is nearly flat molars, usually on the second molars, and or shallowly excavated, its anterior two- sometimes on the third.) thirds entire and not perforated by a large 18. Posterior cingulum: There is a posterior sphenopterygoid opening. (Each fossa is ex- cingulum at the back of each first upper mo- cavated or tilted toward the midline of the lar, usually the second, and sometimes the skull and perforated by a large sphenopter- third. (No posterior cingulum occurs on any ygoid vacuity.) ofthe upper molars, or ifit occurs is indicated 10. Pterygoid platform: The posterolateral only by a triangular bump at the back ofeach portion of each pterygoid platform behind first upper molar.) the foramen ovale is either nearly flat, a low 19. Cusp t9: This cusp is large and discrete mound, or a wide and smooth low ridge. (The on each first and second upper molar. (Cusp edge is thrown up into a definite high and t9 is nearly incorporated into the much larger thin ridge.) cusp t8 and inconspicuous after wear.) 1982 MUSSER: LUZON ISLAND RAT 15

20. Cusp t3: In all or most of the samples, rinae. The structural specializations of Van- cusp t3 is present on the second and often on deleuria are those associated with climbing the third upper molars. (Cusp t3 is absent among slender branches or high grass. Among from the second and third molars in all or living rodents, Vandeleuria has been allied most specimens.) with , , and Chiropodomys 21. Union of cusps: Cusps on the upper (Ellerman, 1941); based on dental characters, and lower molars are weakly connected so Misonne (1969) regarded Vandeleuria to be the occlusal patterns appear strongly cuspi- a close relative of Chiropodomys. date. (All or most cusps are strongly joined, Species of Chiropodomys are also small- some merged to the point where they nearly boddieLand long-tailed, but the tails are pen- lose their identities in several species.) icillate. The fifth digit ofeach hind foot bears 22. Anterolabial and anterolingual cusps: a claw-only the halluces have nails. The The anterolabial and anterolingual cusps on crania of Vandeleuria and Chiropodomys dif- the first lower molar are large and discrete, fer strikingly from that of Abditomys in size forming a lamina nearly as wide as the rest and configuration (fig. 11). The dentitions of of the tooth. (The two cusps are smaller, the two genera are unlike those ofA. latidens. pressed against each other to form a lamina The molars of both Vandeleuria and Chiro- narrower than the rest ofthe tooth. In young podomys are anchored by fewer roots than rats they may be separate but soon merge into are those ofAbditomys (upper first molars are an oblong lamina.) three-rooted, lowers are two-rooted in Chi- 23. Anterolabial cusp: The anterolabial ropodomys; upper first molars are four- cusp on each second lower molar, and often rooted, the lowers two-rooted in Vandeleu- on each third molar, is present in all or most ria); the upper molars either abut against one ofthe samples. (Anterolabial cusps are absent another without overlapping (Chiropodomys) from the second and third molars in all or or overlap slightly ( Vandeleuria), as opposed most of the samples.) to the extensive overlap among the teeth of 24. Fifth digit: The fifth digit on each hind Abditomys; and the molars of Chiropodomys foot bears a claw. (A nail is embedded in each and Vandeleuria have complex and highly fifth digit.) cuspidate occlusal surfaces, unlike the sim- 25. Laminae: The rows of cusps on the ple, laminar-like chewing areas ofA. latidens. upper and lower molars are arcuate or chev- Complexity ofthe occlusal surface in the up- ron-shaped. (The cusps form nearly straight, per molars is partly due to large cusps t7 and laminar-like rows.) posterior cingula on all or most of the teeth, 26. Rows ofcusps: Cusps are weaklyjoined and to large cusps t3 on the second molars. or strongly joined but form uneven rows on Large anterocentral cusps, wide anterolabial the molars. (Large and discrete cusps form cusps on the second and third molars, and two or three straight rows on each molar.) prominent labial cusplets are features of the lower molars contributing to the complex Except for having nails on the halluces, chewing surfaces. Such structures are not Abditomys is unlike Chiropodomys, Hapa- present in the simple molars of Abditomys. lomys, Vandeleuria, Pithecheir, Chiromys- Among the traits listed in table 2, Abdi- cus, or Kadarsanomys in external, cranial, or tomys has many more derived features (17) dental characteristics. I explain below and in than does either Vandeleuria (5) or Chiro- figure 11, where crania of the seven genera podomys (5). No single derivation, other than are compared, and in figures 12 and 13, which nails on halluces, occurs in all three genera. contrast toothrows. Whether Vandeleuria and Chiropodomys are Vandeleuria is arboreal, small-bodied, and as closely related as some taxonomists claim long-tailed. The tail is scantily haired. Digits remains to be tested but neither one seems on the front and hind feet are long and slen- phylogenetically close to Abditomys. der. Both the fifth digit and hallux of each Species of Hapalomys are arboreal and at hind foot have nails. A nail instead of a claw least one of them, H. longicaudatus, is spe- on the fifth digit is unique among the Mu- cialized for living in bamboo and feeding on i V. .,I ".4, O o - 14vi 00

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.a.. r4 --. Fr ~~~-r k AN.I. -A' -*otak SAA. r :: CU* C's *f *Qco i .r *4. ~~~~~~~:~ Ad o I~~~~W> _ a>>^.eCm 1982 MUSSER: LUZON ISLAND RAT 17 it (Medway, 1964). In addition to being relationship to Abditomys, and no derived smaller in body size than A. latidens, and traits are common to only those two genera, differing in coloration and texture of the fur, at least in the characteristics surveyed here. and in basic shape ofthe cranium (especially Although it possesses some highly specialized the interorbital region and braincase), the structures, Pithecheir has far fewer (8) de- species ofHapalomys have different occlusal rived traits than does Abditomys (17), may patterns on the molars. Straight rows of dis- be part of an older group of murines, and crete gleaming cusps form the chewing sur- possibly more closely related to Lenothrix faces of the upper and lower molars, a con- than to anything else (Misonne, 1969). There figuration not found in any ofthe other genera appears -to be no close phylogenetic tie be- discussed here or in the rest of the Murinae tween Pithecheir and Abditomys. in general (figs. 12 and 13). The upper molars Little is known about the habits of Chi- in Hapalomys abut against one another with- romyscus chiropus. The rat is specialized for out overlap. Four roots anchor the first upper arboreal living (Musser, 1981 a) and was molars, the first lower molars are two-rooted. thought to occur in tropical deciduous forest The simple, laminar-like occlusal topogra- (Marshall, 1977). Recently, Joe T. Marshall phy, strong overlap among the molars, and wrote me that he has seen a new specimen additional roots in Abditomys are unlike the of Chiromyscus collected in Thailand from complex, cuspidate occlusal surfaces in Hap- a ravine in which bamboo densely filled the alomys. Except for nails on the halluces, no bottom and broad-leaf tropical forest cov- other derived trait occurs only in Hapalomys ered the upper slopes. Possibly Chiromys- and Abditomys. Misonne (1969) suggested cus-like Chiropodomys, Hapalomys, and that Chiropodomys may be the closest rela- Kadarsanomys-may be ecologically closely tive of Hapalomys. Abditomys is certainly tied to bamboo. A small and low cranium, not. narrow zygomatic plates, wide interorbital Both species of Pithecheir are arboreal, region, postorbital margins and dorsolateral have prehensile tails, and the most grasping sides of braincase defined by shelves, wide type of hind foot in any of the arboreal rats and flat- braincase, a large interparietal roof- and mice noted here (Musser, 1979). Both ing most ofthe occiput, tiny bullae, small and the tail and feet are specialized for climbing low-crowned molars, third molars much on slender supports such as twigs, narrow smaller relative to others in the rows, chev- branches, and palm and fern fronds (Bartels, ron-shaped laminae, no anterolabial cusps on 1937b). The configuration of the cranium- the second and third lower molars, and first particularly the wide interorbital and post- upper molars with four roots are some ofthe orbital regions bordered by wide shelves, the cranial and dental features of Chiromyscus interparietal enclosed on both sides by the that contrast with those of Abditomys (figs. parietals, lack of occipital bulge at the back 1 1-13). Three derived traits (cusp t9 broadly of the braincase, and the large and highly merged with cusp t8 on the first and second inflated bullae-is unlike that in Abditomys upper molars, no cusp t3 on the second and (fig. 11). The upper molars are cuspidate third molars, and all cusps strongly con- rather than laminar-like and have more com- nected) occur in Chiromyscus and Abditomys plex occlusal surfaces due to cusps tlbis at but not in any of the other genera in which the front ofthe first molars, large cusps t7 on the halluces bear nails. Judged from my own the first and second molars, and prominent studies, all three traits have developed at dif- cusps t3 on the second and third teeth. The ferent times and are widely distributed lower molars are also cuspidate: the rows of among African, Indian, and Indo-Australian cusps are chevron-shaped rather than nearly murines. The three features reflect simple transverse, separated farther from one occlusal surfaces, simpler than those found another, and the anterocentral cusp (absent in Chiropodomys or Vandeleuria (figs. 12 and from Abditomys) is bifurcate and large. 13), and do not indicate close phylogenetic Judged from characteristics ofskin, skull, and ties between Abditomys and Chiromyscus. teeth Pithecheir has no close morphological The latter is actually closely related to Nivi- ~zlZ

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19 20 AMERICAN MUSEUM NOVITATES NO. 2730 venter of Southeast Asia and the Sunda Shelf the mesopterygoid and pterygoid fossae (Musser, 1981 a). (Musser, 198 la and 198 lb). Five-rooted first Kadarsanomys sodyi is of medium body upper molars indicate only that A. latidens size, arboreal, and associated with bamboo and K. sodyi are more closely related to each in mountain forests on West Java (Bartels, other than to the species of Chiropodomys, 1937a; Musser, 1981c). The tail is long, Vandeleuria, Hapalomys, Pithecheir, and brown, and monocolored, as is the tail of A. Chiromyscus. The character has no infor- latidens, but the upperparts of the head and mation that can be used to determine whether body are brown, the underparts white, and Abditomys is phylogenetically closer to Ka- the fur short, with very short guard hairs. All darsanomys than to other genera, such as these features are unlike the coloration and Rattus, which have five-rooted first upper length of pelage in Abditomys. In configura- molars. That trait occurs widely throughout tion of the skull and in some dental features, other murines from Africa, India, and the A. latidens is more like K. sodyi than any of Indo-Australian region, genera with clawed the other species discussed here. In both, the halluces. Both A. latidens and K. sodyi must cranium is high, the interparietal is small, the be compared with those forms to determine incisive foramina are long, the palatal bridge whether the two are closely related or whether is short, the pterygoid fossae and alisphenoid they are actually more closely allied to a ge- region are similar in shape, the bullae are nus in which the halluces are clawed. large relative to size ofthe braincase, the up- The configuration of the nail bears further per molars are large relative to the bony pal- study because it differs among the species and ate, each third molar is only a little smaller finer resolution of its structure may provide than the second, the first upper molars are additional information with which to test five-rooted, and the first lowers are four- hypotheses of relationships among the seven rooted. The two species, however, differ in genera. In Hapalomys, Chiropodomys, Van- conspicuous ways: K. sodyi has a shorter and deleuria, and Chiromyscus each nail is small, relatively broader rostrum with relatively nearly flat (slightly convex), with a straight narrower nasals that are convex on top rather or gently arcuate distal margin, and embed- than flat; a wider interorbital region; wider ded in the top of the digital pad. The config- and more prominent shelves along the post- uration is similar to that illustrated for Chi- orbital margins; a more expansive braincase ropodomys in Musser (1979, fig. 14). The nail with straighter sides; relatively narrower zy- ofKadarsanomys is very small relative to the gomatic plates with much shorter anterior size of the large digital pad and embedded in spines; squamosal roots of the zygomatic it, has a highly convex dorsal surface, is short, arches situated lower on sides of the brain- and has a truncate distal margin (Musser, case; shallower mesopterygoid fossa with 1981c, pl. 1). In Abditomys, the base of each much smaller sphenopalatine vacuities, mo- nail is embedded in the top ofthe digital pad lars with low cusps; less overlap among the but the triangular distal margin is not, and upper and lower molars, and occlusal sur- the dorsal surface is moderately convex (fig. faces that are complex and cuspidate rather 4). It is a longer structure relative to size of than simple and laminar-like (figs. 1 1-13). the digital pad compared with the nails in the Abditomys and Kadarsanomys have five- other genera, except for Pithecheir. rooted first upper molars, a derived trait not The nails in Pithecheir are essentially very found in any of the other five genera with short claws (as I called them, Musser, 1979) nails instead of claws on the halluces. The or scalelike claws (in Medway's, 1969, ter- character is significant because it is found in minology) and range in size among the spec- Rattus and many genera distantly and closely imens. On some rats, each structure is short, related to Rattus (Arvicanthis is an example) sits on top of the digital pad, and appears to and usually occurs in combination with other be a pointed nail with a highly convex sur- specializations, such as the derived condi- face. On other specimens, it is larger, over- tions of the alisphenoid region, incisive fo- hangs the pad and resembles a much reduced ramina, size of bullae, and configurations of claw. The configuration is unlike that in any 1982 MUSSER: LUZON ISLAND RAT 21 of the other genera and represents the most ofthe trees in the mossy forests are so heavily primitive state since it is the most clawlike. coated with moss that the observer is easily To me, the structures on the halluces of the deceived as to the actual diameters ofthe tree other genera are good nails (Medway, 1964, trunks. described that in Hapalomys as a flat, nail- "The banks of the deep gullies, that have like scale). The nails in Chiropodomys, Hap- been cut by the descending mountain streams, alomys, Vandeleuria, and Chiromyscus are are also densely vegetated with almost the similar in shape and size relative to the digital same species as those found on the top; but pad and represent the most derived config- never by pine trees. In fact, these gullies are uration. The small, highly convex, and trun- easily traced even at a distance, because the cate nail of Kadarsanomys is distinctive, vegetation growing in them contrasts mark- highly derived, and set apart from the others. edly with the surrounding pine forests." The long, pointed nail of Abditomys is The holotype was caught in the following unique. Based only on configurations of the manner (Rabor, 1955, p. 205): "A member nails, Pithecheir is isolated from the other of the collecting party went out with a net to genera, Abditomys and Kadarsanomys each collect insects. Instead, he caught a big female stands by itself, and Chiropodomys, Hapa- rat in his net. He was chasing insects under lomys, Vandeleuria, and Chiromyscus clus- the pine trees close to the bank of a well- ter. That the nails of the halluces in Abdito- vegetated deep gully, at about 2000 meters mys represent not close phylogenetic affinity elevation, when he saw a large rat apparently with the other six genera but rather indepen- dozing on its haunches, close to a decaying dent derivation seems to be the best hypoth- pine stump. The did not make any esis. attempt to escape even when the collector NATURAL HISTORY was already close to it so that it was easily caught. We found out later that the animal's Little is known about the natural history forefoot was badly swollen due to a bad of Abditomys latidens. The male from Los wound. Doubtless it must have been caught Bafios "was collected from the electric fence in one ofour traps set in the vicinity but had at the International Rice Research Institute- managed to escape with a hurt foot. The bad an area of intensive rice cultivation at an el- foot prevented it from going about its normal evation no higher than 200 feet!" (Barbe- feeding activities, and it was very emaciated henn, Sumangil, and Libay, 1972-1973). The when caught; its stomach was empty when holotype from Mount Data was obtained opened. during the Philippine Zoological Expendition "The palage was stained with intense yel- of 1946-1947. According to Rabor (1955, p. low all over when it was freshly caught, but 197), a member of that expedition, the col- this yellow color faded fast after the animal lection on Mount Data ". . . was made mostly was skinned, especially so when the skin was on the western slope ... at elevations ranging thoroughly dried." from 2000 meters at the base, up to 2310 or Because Abditomys latidens is likely ar- more meters at the very top of the plateau. boreal and may have a special diet, it is ap- The locality was never worked previously by parently rarely encountered by collectors and any collector, because Whitehead ... made unattracted to usual baits. Several external his collections on the eastern and northern features ofA. latidens indicate arboreal hab- slopes of the mountain ...." its: a tail that is much longer than the com- On Mount Data, Rabor (195 5, pp. bined lengths of head and body; long vibris- 195-196) noted that "The vegetation is sae and long guard hairs over most of the mainly pine forest, consisting of pure stands upperparts; large, fleshy, striated pads cov- of Benguet pine (Pinus insularis Endl.), on ering the palmar and much of the plantar the sides; and mossy forest at the top, above surfaces; large digital pads; long claws with the pine belt, consisting mainly of oaks sharp, recurved tips; long and wide hind feet; (Quercus spp.) and mountain yew (Taxus a nail partially embedded in a large, grooved wallichiana Zucc.). The trunks and branches digital pad on each hallux; and probably 22 AMERICAN MUSEUM NOVITATES NO. 2730 some pseudo-opposability of the hallux and negotiated. Some large dead and decaying fifth digit. The relative length of the tail and stems will have fallen on the ground, but structure of the hind feet are adaptive for most ofthem are still erect, supported by the moving about on surfaces above the ground; living stems at different angles. To move over the long tail would provide counterbalance the smooth surfaces of the stems, and to run to the body motion; the fleshy and striated up and down through the hollow internodes, palmar, plantar, and digital pads would pro- requires feet with good adhesive qualities. To vide good adhesion to smooth surfaces; the climb about in the slim twigs at the end of sharp claws would dig into the substrate and bamboo stems, on the other hand requires help maintain balance and position; a short, abilities to grasp and negotiate very slender stout hallux terminating in a large fleshy pad supports. A nail imbedded in a very large and nail would provide the adhesion and distal pad on the hallux apparently is one of strength to enhance the forces involved in the specializations ofthe hind feet associated gripping the substrate; long vibrissae and long with grasping and moving over smooth guard hairs would help detect and distinguish round surfaces." among objects and surfaces in the arboreal Abditomys latidens is probably highly ar- habitat, and also gauge diameters of nest boreal and it may live in bamboo. Its mor- holes. phological traits are consistent with that kind The arboreal adaptations ofbody, tail, and of habitat. The arboreal adaptations of A. feet of A. latidens are complemented by the latidens are similar to those ofKadarsanomys structure of the skull and teeth, configura- sodyi, which is definitely associated with tions possibly reflecting adaptations to deal- bamboo, at least as a nesting site (Musser, ing with fibrous and siliceous substances. 1981c). Neither of the two specimens of A. The cranium of A. latidens is compact, latidens were taken in bamboo but the scanty stocky, and robust. The upper incisors are notes associated with each simply indicates wide, emerge from the rostrum at a right an- they were caught where the collectors hap- gle, and appear strong. The rostrum is short pened to find them. One was found wounded and probably stout enough to absorb the on the ground at the base of a stump, the force generated as the wide incisors are used other was picked up against an electric fence to chip away at hard substances, such as the in a ricefield. Future collectors should look edges around entrance holes into tree cavi- for the species in bamboo, as well as in conifer ties, the internodes of large bamboo stems, and broadleaf forests. or through the partitions between the inter- nodes inside the stem. The high ridges LITERATURE CITED bounding the frontal bones and portions of surface for the Barbehenn, K. R., J. P. Sumangil, and J. L. Libay the parietals offer additional 1972-1973. Rodents of the Philippine crop- origin of temporal musculature. The high, lands. The Philippine Agriculturist, vol. wide, gleaming molars provide large laminar- LVI, nos. 7 and 8, pp. 217-242, 1 fig. like surface areas that suggest a predomi- Bartels, M., Jr. nantly herbaceous diet-leaves, buds, flow- 1937a. A new rat from Java. Treubia, vol. 16, ers, young twigs, for example. pp. 45-46, 1 fig. Some arboreal rats that have nails instead 1937b. Zur Kenntnis der Verbreitung und der of claws on the halluces are associated with Lebensweise Javanischer Saugetiere. bamboo, as either a nesting site or source of Treubia, vol. 16, pp. 149-164. food. Species in Hapalomys, Chiropodomys, Ellerman, J. R. or eco- 1941. The families and genera of living ro- and Kadarsanomys are wholly partly dents. London, British Museum (Nat. logically tied to bamboo (Medway, 1964; Hist.), vol. 2, Family , pp. i-xii, Rudd, 1 979; Musser, 1 979, 198 1c). The mor- 1-690, figs. 1-50. phological adaptations in rats and mice uti- Hill, J. E lizing bamboo are special because, as I noted 1935. The cranial foramina in rodents. Jour. elsewhere (Musser, 1981c, p. 28), "a dense Mammal., vol. 16, pp. 121-129, figs. stand of smooth bamboo stems is not easily 1-3. 1982 MUSSER: LUZON ISLAND RAT 23

Marshall, Joe T., Jr. Hist., vol. 162, art. 6, pp. 377-445, figs. 1977. Family Muridae: rats and mice. Pp. 1-16. 396-487. Reprinted in of 1981a. Results of the Archbold Expeditions. Thailand (Boonsong Lekagul and J. A. No. 105. Notes on systematics of Indo- McNeely). Assoc. Conserv. of Wildlife, Malayan murid rodents, and descrip- Bangkok, Thailand. tions of new genera and species from Medway, Lord Ceylon, Sulawesi, and the Philippines. 1964. The , Hapalomys longi- Ibid., vol. 168, art. 3, pp. 225-334, figs. caudatus Blyth. Malayan Nat. Jour., vol. 1-51. 18, nos. 2 and 3, pp. 104-110, pls. 198 lb. The giant rat of Flores and its relatives XIII-XvIII. east of Borneo and Bali. Ibid., vol. 169, 1969. The wild mammals of Malaya and off- art. 2, pp. 67-176, figs. 1-40. shore islands including Singapore. Kuala 1981c. A new genus of arboreal rat from West Lumpur and Singapore, Oxford Univ. Java, Indonesia. Zoologische Verhan- Press, xix + 127 pp., figs. 1-11, pls. delingen, no. 189, pp. 1-40, pls. 1-4. 1-15. Musser, Guy G., and Patricia W. Freeman Miller, Gerrit S., Jr. 1981. A new species ofRhynchomys (Muridae) 1912. Catalogue of the mammals of Western from the Philippines. Jour. Mammal., Europe (Europe exclusive of Russia) in vol. 62, no. 1, pp. 154-159, figs. 1-2. the collection of the British Museum. Musser, Guy G., and Linda K. Gordon London, British Museum (Nat. Hist.), 1981. A new species of Crateromys (Muridae) pp. i-xv, 1-1019, figs. 1-213. from the Philippines. Ibid., vol. 62, no. Misonne, Xavier 3, pp. 513-525, figs. 1-6. 1969. African and Indo-Australian Muridae. Rabor, D. S. Evolutionary trends. Mus. Roy. l'Afrique 1955. Notes on mammals and birds ofthe cen- Cent., Tervuren, Zool., no. 172, pp. tral northern Luzon highlands, Philip- 1-219, figs. A-K, pls. 1-27. pines. Part I: notes on mammals. Silli- Musser, Guy G. man Journal, vol. 2, no. 3, pp. 193-218. 1970. Species-limits of Rattus brahma, a mu- Rudd, R. L. rid of northeastern India and 1979. Niche dimension in the bamboo mouse, northern Burma. Amer. Mus. Novitates, Chiropodomys gliroides (Rodentia: Mu- no. 2406, pp. 1-27, figs. 1-6. ridae). Malay. Nat. Jour., vol. 32, pp. 1972. The species of Hapalomys (Rodentia, 347-349. Muridae). Ibid., no. 2503, pp. 1-27, figs. Sanborn, Colin Campbell 1-12. 1952. Philippine Zoological Expedition 1977a. Epimys benguetensis, a composite, and 1946-1947. Fieldiana: Zoology, vol. 33, one zoogeographic view of rat and no. 2, pp. 89-158, figs. 8-22. mouse faunas in the Philippines and Thomas, Oldfield Celebes. Ibid., no. 2624, pp. 1-15, figs. 1898. VIII. On the mammals obtained by Mr. 1-4. John Whitehead during his recent ex- 1977b. Results of the Archbold Expeditions. pedition to the Philippines. Trans. Zool. No. 100. Notes on the Philippine rat, Soc. London, vol. 14, part 6, no. 1, pp. Limnomys, and the identity of Limno- 377-414, pls. 30-36. mys picinus, a composite. Ibid., no. Wahlert, John A. 2636, pp. 1-14, 1 fig. 1974. The cranial foramina of protrogomor- 1979. Results of the Archbold Expeditions. phous rodents; an anatomical and phy- No. 102. The species of Chiropodomys, logenetic study. Bull. Mus. Comp. Zool., arboreal mice ofIndochina and the Ma- vol. 146, pp. 363-410, figs. 1-13. lay Archipelago. Bull. Amer. Mus. Nat.