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AMERICAN MUSEUM Novitates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2818, pp. 1-32, figs. 1-19, tables 1-5 June 11, 1985

Philippine Rattus: A New Species from the Sulu Archipelago

GUY G. MUSSER1 AND LAWRENCE R. HEANEY2

ABSTRACT A new species, Rattus tawitawiensis, is de- close relative now living in either the Philippine scribed from Tawitawi Island in the southern Sulu Islands to the east or on the islands and peninsula Islands. It is native to the island, whereas Rattus ofthe Sunda Shelfto the west. In morphology, the rattus mindanensis, which also occurs there is not. Tawitawi rat is most similar to species of Rattus The known mammalian fauna of the Sulu Archi- living on islands rimming the Sunda Shelfbeyond pelago has characteristics indicating that the is- the 180 m bathymetric line. These peripheral iso- lands have had no recent land-bridge connection lates appear to be most similar to Rattus tio- to either Borneo or Mindanao; this is consistent manicus among the extant fauna ofthe Sunda Shelf. with geological evidence. The new species has no INTRODUCTION From September 1971 to January 1972, those species in this report. Two of them, R. members of the Delaware Museum of Nat- exulans and R. rattus mindanensis, are prob- ural History and Mindanao State University ably not native to the Sulu Archipelago. The Expedition collected vertebrates in the South third species, represented by three specimens Sulu Islands (fig. 1). A report of that expe- from Tawitawi Island, is new and endemic dition has been provided by duPont and Ra- to the Sulu Archipelago. Study of that rat bor (1973). Birds were the principal quest of provides significant information relevant to the collectors but a small series of mammals understanding the species diversity, insular was also obtained. Among these were 65 distributions, possible phylogenetic relation- specimens of Rattus representing three ships, and biogeographic histories of Rattus species. We document the identifications of in the Malayan region.

' Archbold Curator, Department of Mammalogy, American Museum of Natural History, New York. 2 Assistant Professor, Museum ofZoology and Division ofBiological Sciences, University ofMichigan, Ann Arbor, Michigan.

FIG. 1. Sulu Islands. Numbers indicate sea depth in meters. Black denotes present-day land areas. Two islands mentioned in text are not labeled: Sanga Sanga Island is off western tip of Tawitawi and Bangao Island just south of Sanga Sanga. During late Pleistocene when sea level was about 120 m lower than at present and during middle Pleistocene when sea level was probably 160 to 180 m lower than now, Tawitawi, Jolo, and the small islands between them would have been part ofone large and elongate island nestled between what would have been the western margin of Sundaland and the eastern edge of a greater Mindanao. Estimates of sea depths and outlines of land areas were made from maps published by the Defense Mapping Center, Washington, D.C., and Operational Navigation Charts published by the Defense Mapping Agency Aerospace Center, St. Louis Air Force Station, Missouri.

ABBREVIATIONS AND PROCEDURES tory, Smithsonian Institution, Washington, D.C. (USNM). The specimens we studied and illustrate Values for total length, length oftail, length here are in collections of the American of hind foot, and length of ear are those re- Museum of Natural History, New York corded by collectors on labels attached to (AMNH); the Delaware Museum of Natural skins. We subtracted length oftail from total History, Delaware (DMNH); the Naturhis- length to obtain length of head and body. torisches Museum, Basel, Switzerland (NMB); Cranial and dental measurements were taken and the National Museum of Natural His- with dial calipers graduated to tenths of mil- 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 3

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FIG. 2. An adult Rattus rattus mindanensis captured on the island of Luzon in the northern Philippines. The photograph was provided by Dr. Kyle R. Barbehenn. limeters. Limits of those measurements are illustrated and defined in Musser (1970) and Musser and Newcomb (1983).

ACKNOWLEDGMENTS To the curators and members of their sup- porting staffs who allowed us to study specimens under their care we are deeply grateful. FIG. 3. Crania of adult Rattus. Left: R. rattus We especially appreciate the loan of material mindanensis, Tawitawi Island (DMNH 3480). to Musser-lots of specimens from several Right: R. rattus diardii, Java (AMNH 250104). institutions. If these specimens had not been Natural size. available at one place and at the specific time, we could not have completed our report. We have also been helped by Ms. Linda K. Gor- One of these is the small-bodied R. exulans, don, who measured specimens housed in the represented by an adult male (DMNH 3531) National Museum of Natural History; from Bongao Island, caught in October 1971. Messrs. Peter Goldberg and Jim Coxe, who Values of external measurements (lengths of are responsible for the photographic prints; head and body, tail, hind foot, and ear are, and Ms. Patricia Wynne, whose fine crafts- respectively, 129 mm, 120 mm, 25 mm, and manship is reflected in figure 6. Finally, we 17 mm), color and texture of fur, shape of thank our colleagues who read the manu- skull, and dentition are typical ofR. exulans, script and provided critical and helpful eval- judged by the hundreds of specimens (in the uations. USNM) from other islands in the Philippines This paper is number 1 14-Results of the that we have examined. Archbold Expeditions. The Asian houserat, R. rattus (fig. 2), is the other species from the Sibutu and Tawitawi THE INTRODUCED RATTUS island groups in the Sulu Archipelago. We studied 61 specimens from the following is- Among the series ofRattus from the south- lands. ern Sulu Archipelago are two species that are found where original habitats have been 1. Sibutu Group, Sibutu Island: DMNH modified or removed: places such as agri- 3474, 3502-3504; all were taken during cultural fields, gardens, and village houses. November197e1. 4 AMERICAN MUSEUM NOVITATES NO. 2818

TABLE 1 Batu: DMNH 3475-3479, 3512-3523, Measurements (in Millimeters) of Adults in Sam- 3526, and 3527; all collected during De- ples of Rattus rattus from the Sunda Shelf, South- cember 1971. ern Sulu Archipelago, and Mindanao (Mean plus or minus one standard deviation, The specimens are large for houserats, with number of specimens in parentheses, and ob- tails longer than the combined lengths ofhead served range are listed.) and body (tables 1 and 2; fig. 2). The fur is coarse with long guard hairs over the back Subspecies and Lengths and rump. Upperparts range from dark tawny Island Skull M'-3 (alveolar) brown through brown to grayish brown; the R. rattus diardiia middle ofthe back is darker and the sides are Sumatra 38.6 ± 1.2 (16) 6.7 ± 0.2 (16) paler, usually grayish yellow or buff. Under- 36.8-40.6 6.2-7.1 parts range from pale and dark gray through Java 40.2 ± 1.7 (20) 6.8 ± 0.4 (20) buffy gray tones to dark brownish buff. Ears 36.6-44.2 5.9-7.3 and feet are brown. The tail is dark brown Bali 42.1 ± 1.0(6) 6.8 ± 0.4(6) throughout its length. Females have 10 mam- 40.6-43.4 6.1-7.0 mae: one pectoral pair, a pair in the postax- Borneo 41.4 ± 0.6 (4) 6.9 ± 0.2 (8) illary region, an abdominal pair, and two in- 40.5-41.8 6.4-6.9 guinal pairs. The specimens are large-bodied versions R. rattusb ofR. rattus diardii, the Asian houserat found Sibutu Island 44.6 ± 2.4 (3) 7.5 ± 0.6 (4) on nearly every island on the Sunda Shelf as 42.6-47.2 6.8-8.1 well as some other places (Musser and Califia, Simunul Island 43.3 ± 1.2 (6) 7.4 ± 0.2 (7) 42.0-45.0 7.1-7.7 1982). It is, for example, common in villages, towns, and larger urban areas on Borneo to Bongao Island 42.9 ± 2.3 (5) 7.1 ± 0.1 (8) the west of the Sulu Archipelago (Medway, 38.9-44.9 6.9-7.3 1977). In body proportion, texture, and color Sanga Sanga 44.0 ± 1.7 (21) 7.4 ± 0.3 (22) of pelage, number of mammae, and confor- Island 40.7-46.9 6.9-7.8 mation of skull and teeth, specimens of R. r. Tawitawi Island 43.2 ± 2.2 (19) 7.6 ± 0.3 (20) diardii and R. rattus from the southern Sulu 38.0-46.4 7.0-8.2 Archipelago are quite similar (fig. 3); body R. rattus mindanensisc size is the primary distinguishing feature. To Mindanao 42.6 ± 2.7 (20) 7.7 ± 0.3 (20) estimate that parameter, we measured great- 37.4-46.1 7.1-8.4 est length ofskull and alveolar length ofmax- a Specimens are in the American Museum of Natural illary toothrow; values from these measure- History. ments are listed in table 1 for samples of R. b Specimens are in the Delaware Museum of Natural r. diardii, the Sulu houserats, and R. r. min- History. danensis, the houserat found on Mindanao c Specimens are in the National Museum of Natural Island in the southern Philippines. Means of History, Smithsonian Institution. skull length and length ofmolar row are clearly less in the samples of R. r. diardii as compared to means from samples of the other 2. Tawitawi Group, Simunul Island: DMNH groups. Specimens from the Sibutu and Ta- 3481-3485, 3501, and 3529; collected witawi island groups resemble those from during October 1971. Mindanao in size, especially in length ofmo- 3. Tawitawi Group, Bongao Island: DMNH lar row. 3486-3488, 3509-3511, 3530, and 3532; Larger average body size is the primary collected during October 1971. difference between samples ofthe Philippine 4. Tawitawi Group, Sanga Sanga Island: houserat and those of R. r. diardii from the DMNH 3287, 3468-3473, 3505-3508, Sunda Shelf. Rattus rattus mindanensis is the and 3533-3543; all taken during October scientific name applied to populations of 1971. Asian houserats on the Philippine Islands 5. Tawitawi Group, Tawitawi Island, Batu (Musser, 1977). We also use this name to 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 5 embrace the populations of R. rattus living on islands in the Sibutu and Tawitawi groups of the Sulu Archipelago. It is unlikely that either R. exulans or R. rattus mindanensis is native to the islands in the Sulu Archipelago. Both live in habitats made and maintained by humans; they are excluded from virgin forests that support a fauna of native rats (Musser, 1977). Their status as commensals and their morphologies contrast sharply with the third species of rat known to occur in the southern Sulus, which is represented by three specimens collected on Tawitawi Island. THE NATIVE RATTUS The three specimens probably represent a species of Rattus native to the Tawitawi Is- land. No specimen like these has ever been collected from the other Philippine Islands that have been sampled for mammals and they are unlike any species known to occur on islands ofthe Sunda Shelf. The specimens do share some morphological features with species native to island groups south of the Shelf, such as the Mentawais, but they have their own combination of distinctive features, which supports the hypothesis that the sample represents a biological species native to the southern Sulu Archipelago. We name, diagnose, and describe the species below.

Rattus tawitawiensis, new species HOLOTYPE: DMNH 3525, the skin (fig. 4) and skull (fig. 5) of an adult female caught at Batu Batu on the southern half of Tawitawi Island, part ofthe Tawitawi Island Group in the Sulu Archipelago ofthe Philippines. The rat was collected by Dr. D. S. Rabor (original number 1390) on December 4, 1971. The skin of the holotype is in good condition but the skull is incomplete. The right zygomatic arch is missing as are the hamular processes. All molars are present (fig. 8). The dentaries are entire. Measurements ofthe holotype are listed in table 2. REFERRED SPECIMENS: From the same place as the holotype come two other examples of R. tawitawiensis, both caught by Dr. Rabor FIG. 4. Stuffed skin of the holotype (DMNH in 197 1. DMNH 3528 is a young adult female 3525) of Rattus tawitawiensis. Measurements are collected on December 7. Although in full listed in table 2. 6 AMERICAN MUSEUM NOVITATES NO. 2818 adult pelage, the animal was probably not 3 to 5 mm thick. Most hairs are gray in their sexually mature because its teats are very basal halves and either unpigmented or buffy small. DMNH 3524, taken on December 4, in the distal portions; the effect is gray tinged is a younger female. It is mostly covered with with silver and buff. On the three specimens, adult fur but there are still large patches of there is a pale, rusty patch either on both juvenile pelage on top of the head between throat and chest, on chest only, or extending the ears and on the rump. Skins ofboth spec- from chin to chest; whether the color results imens are intact, but the crania are damaged from staining or actual pigment within the (fig. 7) due to careless cleaning. Molar rows hairs cannot be determined. are complete (fig. 8). Measurements are listed The appendages are dark. The ears and in table 2. dorsal surfaces of the front and hind feet are KNoWN DISTRIBUTION: Tawitawi Island in dark brown, as are the plantar surfaces and the southern part ofthe Sulu Archipelago (fig. the tail; the palmar surfaces are pale brown. 1). The hind feet are long and narrow. The ETYMOLOGY: Named for the island on plantar surfaces are naked and adorned with which the specimens were collected. six pads. The shape of each foot and the po- DIAGNOSIS: The following combination of sition and size of the pads relative to plantar characteristics sets R. tawitawiensis apart surface area resemble the configuration in from any other species of Rattus: large body Rattus argentiventer (see fig. 2 in Musser, size, tail shorter than combined lengths of 1973). head and body, rich, dark brown upperparts, There is nothing special about the tail. It dark gray underparts, dark brown feet, eight is short relative to length of head and body mammae (one postaxillary pair, an abdom- and dark brown pigment covers all surfaces. inal pair, and two inguinal pairs), a wide and There are 8 to 10 rows of scale hairs per deep cranium, wide incisive foramina, large centimeter (counted at a spot about one-third teeth, prominent anterolabial cusps on a con- the distance from the base of the tail). spicuous cingular ridge on each second and All three specimens are females and four third upper molar, and small bullae relative pairs ofmammae are evident on each animal, to size of cranium. although they are small and inconspicuous DESCRIPrION: This is a large rat with dark on DMNH 3524, the youngest of the series. brown fur and a tail conspicuously shorter There is a postaxillary pair of teats, an ab- than the combined lengths of head and body dominal pair, and two pairs in the inguinal (fig. 4, table 2). The dorsum is covered in region. Most species ofRattus have a pectoral thin, short fur (10 to 15 mm long) over the pair, but such mammae do not occur in R. back. Its overall color is rich, dark brown, tawitawiensis. and uniformly speckled with buff. The inten- The cranium of the adult R. tawitawiensis sity of this deep and dark tone covers the is large, wide, deep, and chunky in general head and body and becomes slightly paler aspect (figs. 5 and 7; table 2). The configu- along the sides due to suffusion of gray. Most ration results from a short and wide rostrum, of the hairs are dark brown or blackish in flaring zygomatic arches (judged by the intact their distal halves and many are tipped with side), and the wide and deep braincase. Seen buff bands; these bands provide the buffy from above, there are ridges forming an an- speckling, which when integrated through the gular outline behind the orbit; the ridges ex- brown fur produces a dark agouti pattern. tend to the back of the skull but diminish in Black guard hairs are short (15 to 20 mm size until they are mere traces delimiting the long), barely extend beyond the overhairs, dorsolateral margins of the braincase. From and are inconspicuous in both presence and the temporal ridges the sides ofthe braincase effect on coloration of the pelage. The fur is flare outward. An oblong interparietal roofs soft to the touch and sleek to the eye despite most of the occipital region. Seen from the the numerous translucent spines scattered side, the zygomatic plates are wide and ex- through the coat-spines that are too soft and tend well anterior to the zygoma. The con- flexible to produce a coarse texture. formation of the alisphenoid region and the The venter is covered with a soft, thin coat, back of the braincase above the bulla is not 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 7

Ij 'i

IItj - PI i.

4 s. i .4e

I .1 .IA C 'A

D2 A B D

;I il A. ,,. ;Ia >' .

-_../ E

FIG. 5. Crania of adult Rattus. A, D, and E: R. rattus mindanensis, Tawitawi Island (DMNH 3480). B, C, and F: R. tawitawiensis, holotype (DMNH 3525). Natural size. Measurements are listed in table 2.

different from the conditions described for The incisors, like those in other species of other species ofRattus (Musser, 1982a; Mus- Rattus, appear strong. Enamel surfaces ofup- ser and Newcomb, 1983). pers and lowers are orange. As viewed from a ventral aspect, the cra- Occlusal surfaces of upper molars in each nium is also similar to other species ofRattus ofthe three specimens ofR. tawitawiensis are in several respects. The incisive foramina, shown in figure 8. The toothrows are long which extend past the anterior margins ofthe and the molars wide relative to size of the first molars; the long palatal bridge, which cranium (table 2). The general occlusal pat- projects behind the third molars to form a terns, shape ofeach tooth and its size relative shelf; the spacious sphenopalatine vacuities; to the others in the toothrow, degree of over- the configuration of the pterygoid fossae and lap among molars in a toothrow, and number the basicranial region, which reflects a certain of roots anchoring each tooth are like those carotid circulatory pattern, are basic to species features in many other species of Rattus of Rattus (Musser, 1982a). The distinctive (Musser, 1982a; Musser and Newcomb, characteristics of R. tawitawiensis are the in- 1983). cisive foramina, which are not just long but There are details in the cusp patterns ofR. very wide, the small bullae (relative to cranial tawitawiensis that deserve description. In each size), and the large, chunky molars. first upper molar ofDMNH 3525, the second The general aspect of each dentary is like row of cusps is united by an enamel bridge that in other species of Rattus (fig. 5). It is to the third row (clearly seen in fig. 8A). In distinctive in its stout appearance, deep ra- the two younger rats, the labial cusps of the mus, and deep triangular-shaped portion be- first and second rows on each first upper mo- hind the ramus. lar have a ridge-like posterior extension, a 8 AMERICAN MUSEUM NOVITATES NO. 2818 configuration seen most clearly in figure 8C. areas close to the Batu Batu area, have been Such an extension is present but slight on the logged and eventually cleared fully, then labial cusp ofthe first lamina on each second planted to various crops." Those authors also upper molar. Although the teeth are worn in note that large areas in the southern half of the oldest specimen, there is still an indica- Tawitawi Island are covered by second- tion of a posterior cingulum at the back of growth forest. Unfortunately, we have no in- each first upper molar. A large and conspic- formation about the particular habitat where uous posterior cingulum also forms the back samples of either R. tawitawiensis or R. rat- of not only the first upper molar but also the tus mindanensis in the Batu Batu region were second in the youngest animal, DMNH 3524 obtained. One specimen of R. rattus was (see fig. 8C); DMNH 3528 lacks posterior caught in a house, but there are no data as- cingula on the upper molars. In all three spec- sociated with any of the other animals. We imens there is a small or large prominent cusp suspect that R. rattus is common in the fields developed from a conspicuous cingular ridge and villages, whereas R. tawitawiensis orig- at the anterolabial margin ofeach second and inally lived in high forest but now occurs in third upper molar. In each second upper mo- second-growth forest and scrub, at least in lar, the small labial cusp juts forward so that the southern half of the island. it nearly touches the back ridge of the cusp We know nothing about the habits of R. forming the labial margin ofthe first lamina. tawitawiensis. Because of its stout body, tail Finally, the first lamina of each third upper that is shorter than length of head and body, molar is slightly undulate, not bent into the and long, slender hind feet, we think it to be shape of a comma as in R. rattus. terrestrial. Its dark coloration suggests habi- The lower molars are also large and chunky tation in good cover and we suspect that the (fig. 8) and, in general shape, cusp patterns, animal is a rat ofthe forest floor. Its diet and and numbers ofroots, resemble teeth in other reproductive characteristics are unknown. species of Rattus. There are small but conspicuous anterior and posterior cusplets on the labial side ofeach first lower molar. Each COMPARISONS second molar bears a posterior labial cusplet. The definition ofany new species involves The cusp at the anterolabial margin of each notjust description but comparisons with re- second and third tooth is large and present lated species as well. We present those com- in all three specimens. It may be significant parisons here, realizing that because our sam- that the anterolabial and anterolingual cusps ple ofR. tawitawiensis is small, each specimen forming the front lamina of each first molar is of a different age, and only one sex is rep- are coalesced-even in the youngest rat in resented, certain characteristics we now de- which the chewing surfaces are only slightly tect as important may lose their significance worn (fig. 8c). Usually in a specimen ofRattus in larger samples that would better estimate ofthat age the two cusps are discrete and form the range of morphological variation within a bilobed, rather than an oblong, lamina in the species. cross-section (fig. 8f). We will contrast Rattus tawitawiensis with HABITATS AND HABITS: Batu Batu, the place several other species of Rattus. One com- where the specimens ofR. tawitawiensis were parison involves the Tawitawi animals and caught, is in the southern coastal lowlands on our specimens ofR. rattus mindanensis from the western third of Tawitawi Island. The the Sulu Archipelago. Then we compare the northern half of the island is mountainous, three specimens of R. tawitawiensis with the highest elevation about 1800 feet (see the samples of R. tiomanicus mara from the terrain diagram in King and McKee, 1949). Maratua Archipelago off the east coast of According to duPont and Rabor (1973, p. 8), Borneo, with R. hoffmanni from Sulawesi, the "largest and most intact areas of dipter- with R. stoicus from the Andaman Islands ocarp forests, many of which have not yet west ofthe Malay Peninsula, and with mem- been touched by man, are found in the north- bers of the R. palmarum group from Pulau ern half on Tawitawi Island. Those in the (Island) Enggano, the Mentawai Islands, Pu- southern half of this island, especially the lau Simalur and adjacent islands, and the Ni- 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 9

FIG. 6. The Sunda Shelf and offshore islands. The dotted line denotes the 100 fathom (180 m) line. Note that the islands and island groups of Tawitawi, Maratua, Sulawesi, Enggano, Simalur, Nicobar, and Andaman lie beyond the 100 fathom line. Sea level lowered to about 180 m during the Pleistocene would not have been enough to connect most ofthese islands with the continental margin of Sundaland. The Mentawais were probably an exception, and may have been connected to the mainland by a narrow isthmus. cobar Islands. The threads connecting these ilar to R. tawitawiensis as are certain exam- samples of Rattus are their morphological ples from islands off of the Sunda Shelf. similarity to R. tawitawiensis and their hab- We begin with the distinctions we see be- itation on islands off of the Sunda Shelf between specimens ofR. tawitawiensis and those yond the 180 m (100 fathom) bathymetric of the houserats taken in the Batu Batu area. line (fig. 6). We have also considered and examined samples of other species, but will Rattus tawitawiensis and not discuss them in detail because the com- Rattus rattus mindanensis parions were unnecessary to define R. tawitawiensis. Except for R. tiomanicus on the Contrasting these two species is important Shelf, which we will discuss later, no other because species ofRattus with a morphology species of Rattus is as morphologically sim- similar to that of R. tawitawiensis are often 10 AMERICAN MUSEUM NOVITATES NO. 2818

TABLE 2 Measurements (in Millimeters) Contrasting Specimens of Rattus tawitawiensis with Samples of Rattus rattus mindanensis from the Southern Sulu Archipelago (Mean plus or minus one standard deviation, number of specimens in parentheses, and observed range are listed.) Species and Age Group Older Adult Adult Young Adult Young Adult-Juvenile Measure- ments R.t.a R.r.m.b R.r.m.c R.t.d R.r.m.e R.t/ R.r.m. LHB 208 199.2 ± 4.1 (5) 191.0 ± 10.6 (9) 171 167.8 ± 11.8 (4) 160 175 157 194-205 178-212 151-178 LT 180 197.0 ± 10.9 (5) 189.9 ± 13.0 (9) 161 191.0 ± 10.9 (4) 146 166 158 192-215 170-205 176-205 LHF 42 40.6 ± 0.9 (5) 40.8 ± 1.5 (9) 41 40.5 ± 1.9 (4) 39 36 36 40-42 39-43 39-43 GLS 46.5 45.8 ± 0.5 (4) 43.9 ± 0.7 (9) 42.1 41.5 ± 0.9 (4) 41.0 39.5 38.0 45.3-46.4 44.9-43.0 40.3-42.4 IB 6.7 6.6 ±0.3 (5) 6.3 ± 0.2 (9) 6.1 6.0 ± 0.2 (4) 5.7 5.8 5.6 6.3 -7.0 6.0-6.5 5.8-6.1 LR 14.5 14.3 ± 0.2 (5) 13.4 ± 0.4 (9) 12.7 12.5 ± 0.5 (4) 12.5 11.9 11.6 14.1-14.5 12.6-14.1 11.9-13.1 BR 8.9 8.1 ± 0.5 (5) 7.6 ± 0.3 (9) 7.7 7.0 ± 0.1 (4) 6.7 6.5 6.5 7.7-8.7 7.0-8.1 6.9-7.1 BZP 5.5 4.5 ± 0.1 (5) 4.5 ± 0.2 (9) 4.6 4.0 ± 0.2 (4) 4.1 3.7 4.1 4.4-4.7 4.2-4.7 3.7-4.2 BBC 18.2 16.8 ± 0.3 (5) 17.0 ± 0.5 (9) 16.6 16.5 ± 0.3 (4) 16.2 15.5 15.5 16.6-17.3 16.4-17.7 16.2-16.9 HBC 12.9 12.1 ± 0.3 (5) 11.9 ± 0.6 (9) 12.6 11.8 ± 0.1 (4) 11.0 11.2 10.5 11.9-12.4 11.2-13.0 11.7-11.9 PL 25.2 24.8 ± 0.6 (5) 23.8 ± 0.3 (7) 22.8 22.2 ± 0.3 (4) 22.0 20.1 20.4 24.1-25.4 23.4-24.2 21.8-22.4 LD 12.1 12.2 ± 0.5 (5) 11.2 ± 0.4 (8) 10.2 10.7 ± 0.2 (4) 10.2 9.3 9.7 11.7-13.0 10.8-11.8 10.5-10.9 LIF 8.6 8.8 ± 0.5 (5) 8.4 ± 0.3 (9) 8.1 7.9 ± 0.6 (4) 7.7 6.7 7.0 8.1-9.2 7.7-8.8 7.1-8.5 BIF 3.9 3.1 + 0.1 (5) 2.8 + 0.1 (8) 3.1 2.5 + 0.1 (4) 3.0 2.7 2.5 2.9-3.2 2.6-3.0 2.3-2.6 LPB 9.6 9.0 ± 0.5 (5) 9.1 ± 0.5 (7) 8.3 8.3 ± 0.3 (4) 8.4 8.1 7.9 8.2-9.5 8.6-9.8 8.1-8.7 BPBM1 5.0 3.9 ± 0.2 (5) 3.9 ± 0.3 (8) 3.9 3.8 + 0.1 (4) 3.9 3.0 3.5 3.6-4.2 3.5-4.2 3.7-3.9 PPL 15.0 15.9 ± 0.3 (5) 14.9 ± 0.3 (7) 13.3 14.0 ± 0.2 (4) 13.0 13.4 12.7 15.5-16.3 14.3-15.3 13.8-14.2 LB 6.9 7.7 ± 0.2 (5) 7.3 ± 0.3 (8) 6.5 6.8 ± 0.1 (4) 6.6 6.7 6.0 7.3-7.9 7.0-8.0 6.6-6.9 ALM1-3 8.0 7.6 ± 0.4 (5) 7.7 ± 0.2 (8) 7.9 7.4 ± 0.3 (4) 8.2 7.6 7.1 7.3-8.2 7.3-7.9 7.0-7.7 CLM1-3 7.2 6.7 ± 0.1 (5) 6.9 ± 0.2 (9) 7.6 6.8 ± 0.3 (4) 7.7 6.8 6.6 6.6-6.9 6.6-7.2 6.4-7.1 BM' 2.2 2.0 ± 0.1 (5) 2.0 ± 0.1 (8) 2.2 2.0 ± 0.0 (4) 2.3 2.0 2.0 1.9-2.1 1.9-2.1 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS I1I misidentified as R. rattus. Values from mea- brown ears and feet, its dark and rich brown surements are listed in table 2. The older adult fur uniformly speckled with buff, and absence specimen of R. tawitawiensis can be com- ofblack streaking because the guard hairs are pared with older adults of R. r. mindanensis very short and inconspicuous. In addition to of about comparable age as well as median- color, there is a difference between the two age adults; also, the young adult and young species in fur texture: that of R. r. minda- adult-juvenile R. tawitawiensis can be con- nensis is harsher to the touch compared with trasted with specimens of R. r. mindanensis the softer and sleeker coat of R. tawitawien- of comparable age. The age categories are 5i5. based on degree of molar wear and cranial There are distinctions between the two conformation. We tried to match each spec- species in color of the ventral coat. Pale gray imen of R. tawitawiensis with specimens of to grayish buffy brown is the range found in R. r. mindanensis that we judged to be about most samples of R. r. mindanensis; the three the same age. Skulls are compared in figures specimens ofR. tawitawiensis have dark gray 5 and 7 and occlusal views of molar rows in venters with silver or very pale buffy high- figure 8. The two kinds of rats are similar in lights. body size but dissimilar in body and tail pro- Female R. r. mindanensis have five pairs portion. In any sample of R. r. mindanensis, ofmammae; the number and general location tails average about as long or longer than av- of the ten teats are similar in the hundreds erage length of head and body; in each spec- of specimens of R. r. mindanensis that we imen of R. tawitawiensis, the tail is much have examined from places throughout the shorter than head and body. Philippine Islands. Rattus tawitawiensis has The contrast between the two in color of four pair; it lacks pectoral teats, which are the dorsal coat is striking. Rattus r. minda- present in R. r. mindanensis. nensis is a paler animal. The ears are medium Cranial differences are conspicuous. Rattus brown, the brown on tops of the feet tends tawitawiensis has a wider and deeper cranium to be restricted to a mid-dorsal strip extend- than does R. r. mindanensis. When compa- ing from the ankle to base of the digits, and rable-age specimens of the two species are the head and body is grayish brown in some examined, this difference is reflected in specimens and grayish tawny brown in many breadth of rostrum, breadth and height of others. Furthermore, the gray-brown is braincase, and breadth of palatal bridge at densely streaked with black over the back and first upper molars. The two rats differ further rump, an effect caused by the very long (up in that R. tawitawiensis has a broader zygo- to 40 mm) and abundant guard hairs, a fea- matic plate, much wider incisive foramina, ture characteristic of Asian houserats. and smaller bullae. In addition, the postor- Compared with R. r. mindanensis, R. ta- bital ridging begins farther back on the cra- witawiensis is easily distinguished by its dark nium than in R. r. mindanensis.

a DMNH 3525, holotype of Rattus tawitawiensis. bDMNH 3480, 3513, 3517, 3519, and 3522. cDMNH 3475, 3478, 3512, 3514-3516, 3523, 3526, and 3527. d DMNH 3528. eDMNH 3476, 3477, 3479, 3518, and 3521. fDMNH 3524. g DMNH 3518 and 3520, respectively. Abbreviations: LHB, length of head and body; LT, length of tail; LHF, length of hind foot; GLS, greatest length of skull; IB, interorbital breadth; LR, length of rostrum; BR, breadth of rostrum; BZP, breadth of zygomatic plate; BBC, breadth of braincase; HBC, height of braincase; PL, palatal length; LD, length of diastema; LIF, length of incisive foramina; BIF, breadth ofincisive foramina; LPB, length ofpalatal bridge; BPBM', breadth ofpalatal bridge at first upper molar; PPL, postpalatal length; LB, length of bulla; ALM'-3, alveolar length of maxillary toothrow; CLM'-3, crown length of maxillary toothrow; BM', breadth of first upper molar; R.t., Rattus tawitawiensis; R.r.m., Rattus rattus mindanensis. 12 AMERICAN MUSEUM NOVITATES NO. 2818

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9 . VA#.' .s E (K d At!Q 4~ FIG. 7. Crania of Rattus tawitawiensis and R. rattus mindanensis compared. Rattus tawitawiensis: A and a, DMNH 3525; B and b, DMNH 3528; C and c, DMNH 3524. Rattus rattus mindanensis: D and d, DMNH 3480; E and e, DMNH 3477; F and f, DMNH 3520. Natural size. An adult, young adult, and very young adult are represented in the three examples of R. tawitawiensis. Each specimen of R. r. mindanensis is a counterpart of R. tawitawiensis in age.

Contrasts between the species in shape of large cusp, but all are pressed against the front dentaries reflect a cranial distinction. Each lamina and not part ofa singular ridge form- dentary ofR. tawitawiensis is deeper through ing the anterolabial margin of each tooth, as the ramus and the posterior half than those is the configuration in R. tawitawiensis. Only of R. r. mindanensis (fig. 5). five of the 19 examples of R. r. mindanensis The molar rows are longer in the three ex- have either a tiny or small cusp at the antero- amples ofR. tawitawiensis than in most spec- labial corner ofeach third upper molar; such imens of R. r. mindanensis and the molars a cusp is large and developed on a cingular wider, using width of each first upper molar ridge in all specimens of R. tawitawiensis. as a guide. Occlusal patterns are generally Posterior cingula occur on first upper molars similar in the two species but different in de- in three out of 18 specimens of R. r. min- tails. Rattus rattus mindanensis does not have danensis. The frequency is higher in R. tawi- the posterior ridge-like extensions on labial tawiensis; two out of three have the cusps. cusps of first and second upper molars; such Finally, the front lamina of each third upper ridges are prominent in R. tawitawiensis. Out molar is shaped like a comma in the house- of 19 specimens ofR. r. mindanensis, 13 have rats but is only slightly undulate in R. tawi- anterolabial cusps on each second upper mo- tawiensis. lar that range in size from a tiny lump to a We have compared our sample of R. tawi- 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 13

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FIG. 8. Upper and lower molar rows of Rattus tawitawiensis and R. rattus mindanensis compared. Top row, R. tawitawiensis: A and a, DMNH 3525; B and b, DMNH 3528; C and c, DMNH 3524. Bottom row, R. rattus mindanensis: D and d, DMNH 3519; E and e, DMNH 3477; F and f, DMNH 3521. Approximately x 10. Arrows point to features discussed in text. Each example of R. rattus mindanensis is an approximate age counterpart of each R. tawitawiensis. tawiensis with specimens of R. r. mindanen- and its fur is pigmented more like that of sis; these are the only two species taken so houserats. It does have four pairs of mam- far on Tawitawi Island. Throughout the Sulu mae, but one is pectoral, another is postax- Archipelago, the only other species ofRattus illary, and two pairs are inguinal. These po- known to occur on some islands (Bongao, for sitions in the pectoral and abdominal regions example) is R. exulans. This is a very small- are different from locations of teats in R. ta- bodied rat compared with R. tawitawiensis, witawiensis. Other species of Rattus may be 14 AMERICAN MUSEUM NOVITATES NO. 2818

about 28 nautical miles east ofTanjong Batu, the nearest point on the mainland (see map in Musser and Califia, 1982, p. 4). The native rat of this small archipelago is Rattus tiomanicus mara, an insular morphological variant of a species that occurs on the Malay Peninsula and most large and small islands ofthe Sunda Shelf. But for a few places, it has not been found on islands offthe Shelf- the Maratua Archipelago is one exception. The subspecies is large in body size compared with samples ofR. tiomanicus from any other place, the upperparts are dark chestnut, and the underparts dark gray to dark buffy gray. Musser and Califia (1982) have documented the taxonomic history associated with samples from the Archipelago, discussed the identity ofthe animals, compared them with samples of R. tiomanicus from other places, and presented a hypothesis about their relationships to samples from populations of R.

size. ~ io't tiomanicus from other islands off the east coast of ~ Borneo and from the mainland. Because R. tiomanicus mara is large in body size compared with all other samples of the FIG.~~9. species, especially those from mainland Bor- neo, and because it has dark pelage and comes 1974). from islands off the Sunda mara,(USN we tua checked Shelf, to see if it could be related to R. tawitawiensis, another large-bodied and darkly pigmented species from an island east of the Shelf. We detect no special relationship between R. tawitawiensis and R. tiomanicus mara other than the fact that they represent insular natveo TwitwiIsland and other islands populations of Rattus. Both have dark fur in the Sulu Archipelago, but that can be de- and a similar general aspect ofthe skulls, but termined only by future mammalogical ex- R. tawitawiensis is a much larger rat with ploration in the archipelago. We now turn bigger teeth (table 3). The wider, more spa- our attention to samples of Rattus from out- cious (relative to diastemal region) incisive side the Sulu Islands, samples that must be foramina ofR. tawitawiensis compared to that compared with the three specimens of the in R. t. mara is striking (fig. 9). The R. tio- native Tawitawi rat. manicus mara female has five pairs of mammae, as does R. r. mindanensis, but not R. tawitawiensis. The from Rattus tawitawiensis and samples Kepulauan Rattus Maratua represent insular populations of R. tiomanicus mara tiomanicus occurring offthe Sunda Shelf; the Lying east of the Bornean mainland, be- three specimens of R. tawitawiensis are not yond the 180 m bathymetric line between 2 samples of another dark and large-bodied and 3°N. lat., Pulau Maratua and the smaller population of R. tiomanicus; they are a dif- islands ofAlanga, Tong Tutup, Sangalan, and ferent biological species. Bakungan form a small cluster known as the The next samples to be compared with Maratua Archipelago (Kepulauan Maratua) specimens ofR. tawitawiensis come from the 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 15 island ofSulawesi and represent a species that TABLE 3 also has eight pair of mammae. Measurements (in Millimeters) from Samples of Rattus Rattus tawitawiensis and (Mean plus or minus one standard deviation, number of specimens in parentheses, and ob- Rattus hoffmanni served range are listed.)a Located south ofthe Sulu Archipelago and separated from it by the deep Celebes Sea, Lengths Sulawesi (Celebes) is a large island directly Species and Ml-3 east of Borneo and beyond the Sunda Shelf. Island Skull (Alveolar) Rattus hoffmanni is one of 35 species native R. tiomanicus sabae, Borneo to Sulawesi (Musser, 1984). Because it occurs Sampit 38.1 ± 1.6(17) 6.8 ± 0.2 (19) on an island east of the Sunda Shelf, because 34.8-41.3 6.4-7.2 its general morphology resembles that of R. tawitawiensis (and it is the only species of R. tiomanicus mara, Borneo Sulawesian rat that does), and because Su- Pulau Maratua 43.1 ± 2.1 (30) 7.1 ± 0.2 (27) lawesi is the first large island south of the 39.7-47.4 6.7-7.6 Sulu chain, we compared samples of the two R. tawitawiensis, Sulu Arch. species to determine the extent of their re- DMNH 3525 46.5 8.0 lationship, if any. DMNH 3528 42.1 7.9 Rattus hoffmanni is a common element of DMNH 3524 41.0 8.2 the fauna on Sulawesi and lives in forests that R. hoffmanni

extend from coastal lowlands to mountain Central Sulawesi 42.3 ± 1.5 (17) 7.8 + 0.1 (20) summits. It has a moderately large body and 40.2-45.0 7.5-8.3 a tail about as long as combined lengths of R. adustus head and body. Fur clothing the dorsum is Pulau Enggano 8.7 soft, thick, and short. The overall coloration is brown speckled with buff, producing a dark R. lugens, Mentawais agouti pattern. Top ofthe back and rump are Pulau Pagi Utara 48.1 ± 1.7(23) 8.1 ± 0.2 (23) darker than the grayish sides ofthe head and 45.5-50.8 7.7-8.5 body. The ventral coat ranges from dark gray Pulau Sipora 46.2 ± 1.9 (15) 7.8 ± 0.3 (12) to dark grayish brown. The ears, tops of feet, 43.0-48.9 7.3-8.4 and tail are brown. Females have four pairs R. simalurensis of mammae: one postaxillary pair, an ab- Pulau Simalur 444.7 ± 1.4 (11) 7.7 ± 0.2 (12) dominal pair, and two pairs in the inguinal 442.8-47.3 7.5-8.0 region-there is no pectoral pair, a pattem of Pulau Lasia and 465.4 ± 2.0(12) 7.9 ± 0.2 (12) teats similar to that in R. tawitawiensis. The Pulau Babi 443. 1-50.9 7.6-8.3 cranium resembles that of Asian houserats R. burrus, Nicobars but is more the molars are robust; large. Great Nicobar 411.6 ± 2.6 (3) 7.6 ± 0.1 (3) Seven scientific names have been applied Island 338.8-43.9 7.6-7.7 to R. samples of hoffmanni. The proliferation Trinkut Island 433.1 ± 1.7 (10) 7.7 ± 0.1 (12) reflects the good representation ofthe species 441.3-46.7 7.4-7.9 in collections of museums and the fact that R. palmarum, Nicobars through the years different taxonomists described what considered to be NMW B-27 54.0 9.0 they significant NMW 27027 51.0 8.9 geographic variation among the samples. A NMW B-26 49.0 9.0 preliminary study by Musser (1984), however, indicates that most ofthe names do not R. stoicus, Andamans designate different populations with distinc- Henry Lawrence 50.0 ± 2.3 (14) 8.3 ± 0.3 (16) tive morphological attributes and geographic Island 46.4-55.1 7.6-8.6 boundaries. Geographic variation among South Andaman 50.2 ± 3.0 (7) 8.3 ± 0.2 (8) samples from throughout most of the island Island 46.4-55.1 8.0-8.7 is slight; the exception is a small lot of spec- a All specimens are adults except for DMNH 3524. J \

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16 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 17 imens from the southwestern peninsula, skull, a place farther back than on specimens which may represent a subspecies different of other Rattus, such as R. rattus mindanen- from the population on the rest of Sulawesi. sis, for example); (3) a deeper braincase; (4) Rattus tawitawiensis is larger in body size a narrower and deeper interparietal; (5) con- than most specimens of R. hoffmanni. An spicuously wider incisive foramina -with few occasional example of the latter, such as exceptions, the incisive foramina are slitlike AMNH 101258, equals R. tawitawiensis in in R. hoffmanni; (6) and smaller bullae rel- size, but the contrasts between examples of ative to skull size (values from the ratio, length R. tawitawiensis and most specimens of R. of bulla divided by length of skull is 15 per- hoffmanni ofcomparable age resemble those cent in the adult and young adult R. tawi- shown in figure 10 where the cranium of the tawiensis and an average of 17 percent in 20 adult R. tawitawiensis is compared with cra- specimens of R. hoffmannO). nia of adult R. hoffmanni from samples rep- Teeth ofthe two species are similarin length resenting the geographic series which had re- ofmolar row, width ofeach first upper molar, ceived scientific names. and occlusal patterns (fig. 1 1). A contrast be- The two species are not so different in coat tween the two species, although not pro- color. In both, the fur is soft, the upperparts nounced, is that most specimens of R. hoff- are brown with buffy speckling, and the guard manni lack ridges on the posterior margins hairs are short and inconspicuous. The tone of labial cusps on the first and second upper in R. tawitawiensis, however, is darker and molars, ridges which are conspicuous in the richer than in most examples of R. hoffman- examples of R. tawitawiensis. ni, and the intensity extends over the entire In pelage features, number of mammae, dorsum. Most specimens of R. hoffmanni many aspects of cranial conformation, and have a paler coat and the sides of head and dental characteristics, specimens of R. tawi- body are definitely grayish and paler than the tawiensis and R. hoffmanni are similar. There top of the body; other specimens, however, are differences, however, and these are ofthe are as dark or even darker than those of R. kind and magnitude that we have found to tawitawiensis and some of these animals are distinguish other species of Rattus from one nearly indistinguishable from specimens of another. There is no evidence from our sam- the Tawitawi rat. Color ofthe ventral coat in ples that the series from Tawitawi Island rep- R. hoffmanni resembles that of R. tawita- resents an insular subspecies ofR. hoffmanni, wiensis, but most specimens are a more solid even though the two species share many mor- and darker gray, and many others have a phological features, including four pairs of brownish or dark buffy suffusion -hues which mammae and relatively large molars. are uncharacteristic of the ventral fur of R. Four pairs of teats are characteristic of tawitawiensis. another species of Rattus that is found on Basic configuration of the cranium in the islands well separated from the Sunda Shelf. two species is not strikingly dissimilar (fig. That animal is the next subject and to set the 10); the distinctions are of small magnitude context for our comparisons we have tojump as they tend to be among some species of from Sulawesi, off the eastern edge of the Rattus. In addition to the greater size of R. Sunda Shelf, all the way to the Andaman Is- tawitawiensis as compared with most ex- lands, which lie west of the Shelf margin. amples of R. hoffmanni (table 3), the Tawi- tawi rat differs in having (1) a chunkier skull, Rattus tawitawiensis and largely a result of its relatively wider and Rattus stoicus shorter rostrum (values from the ratio, Rattus stoicus is native to the Andaman breadth of rostrum divided by length of ros- Islands; we have examined specimens from trum, are 61 percent in DMNH 3525 and Henry Lawrence Island, South Andaman Is- 3528 as opposed to 56 percent, the mean of land, and Little Andaman Island. The species 20 R. hoffmanni from Central Sulawesi); (2) was named and described by Miller in 1902; heavier ridges bounding the postorbital mar- taciturnus Miller (1902), and rogersi Thomas gins on top of the cranium (but the ridges (1907), also apply to the same species. A re- begin at about the same level on top of the port now being prepared (Musser and Mi- 18 AMERICAN MUSEUM NOVITATES NO. 2818

,li.i A FIG. 1 1. Upper molar rows ofRattus tawitawiensis and Rattus hoffmanni. A, R. tawitawiensis (DMNH 3524). B (AMNH 224961) and C (AMNH 224252), R. hoffmanni, central Sulawesi. Approximately x 10. On all three, note the posterior cingulum at the back of each first molar and the cusp at the anterolabial margin of each second and third molar (indicated by arrows on A). sonne, Ms) will document the taxonomy, nat- and paler than examples ofthe Tawitawi rats. ural history, and phylogenetic relationships The tail of R. stoicus is also paler than that of the rat. in R. tawitawiensis and instead of being Rattus stoicus, like R. tawitawiensis, is monocolored, its ventral surface is mottled large-bodied, has a tail much shorter than and much paler than the top. The front feet length ofhead and body, possesses four pairs of the Andaman rat are white with a thin of mammae, and is found only on islands grayish brown strip extending over the top to beyond the Sunda Shelf. With these points, the base of the digits; the hind feet are un- however, any close resemblance ends. Judged pigmented or very pale grayish brown -very by length ofskull, specimens ofthe Andaman distinctive when compared with the dark rat are larger than those of R. tawitawiensis brown feet of R. tawitawiensis. Aside from and have longer molar rows (table 3). The relative tail length and n-umber of mammae, dorsal fur ofR. stoicus is grayish brown, shag- no special relationship between the two gy in appearance, very coarse to the touch species is indicated by pelage characteristics. because of the many semi-rigid translucent Our comparisons of skulls and teeth in the spines scattered throughout the pelage, and two samples also point to a distant morpho- topped by long guard hairs (up to 50 mm logical relationship between R. stoicus and long) that extend conspicuously beyond the R. tawitawiensis. The Andaman animal has overhair over the back and rump. The fur an elongate cranium with a very long and contrasts sharply with the relatively soft and slender rostrum; the contrast between the two sleek pelage ofR. tawitawiensis with its short species is seen in figure 12. The elongate cra- guard hairs and dark brown agouti pattern. nial conformation ofR. stoicus is also evident Fur clothing the venter in R. stoicus is gray from a ventral view where two additional 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 19

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t .+} t, ilN. . FIG. 13. Upper molar rows. Left: Rattus tawi- ,o'.4 S.%'t ,; tawiensis (DMNH 3528). Right: Rattus stoicus, Henry Lawrence Island, the Andamans (USNM k-) I 1 1830). Note the absence ofcusps at anterolabial * . s W margins of second and third molars of R. stoicus, b and the C-shaped occlusal pattern ofthe third molar. Approximately x 10.

t _ _'L v _

FIG. 12. Crania of adult Rattus. Left: R. tawi- ied, short-tailed, insular endemic, we detect tawiensis (DMNH 3525). Right: R. stoicus, Henry no morphological evidence linking it closely Lawrence Island in the Andamans (USNM to R. tawitawiensis. This is not the same pic- 11 1845). Natural size. ture we saw after comparing samples ofRat- tus from islands off the southern margin of the Sunda Shelf with specimens of the Tawi- tawi rat, as we explain below. distinctions can be seen: (1) the incisive foramina are much longer narrower in and R. Rattus tawitawiensis and the stoicus, and their posterior margins lie an- Rattus palmarum Group terior to the molar rows instead of extending between the molars as they do in the Tawi- We apply the name palmarum group, as tawi rat; and (2) the sphenopalatine vacuities did Musser and Califia (1982), to samples of of R. stoicus are small, not spacious as they Rattus from the Nicobar Islands and from are in R. tawitawiensis and most other species the islands off the southwestern coast of Su- of Rattus (Musser, 1 982a). Distinctions be- matra beyond the 180 m bathymetric line. tween the two species in molar occlusal pat- Scientific names included within the group, terns (fig. 13) are of the kind and degree seen their authors and dates of publication, and between specimens of R. tawitawiensis and the island from which each holotype was ob- R. rattus mindanensis. tained are listed in table 4. The series contains So, even though R. stoicus is a large-bod- specimens of large-bodied rats, some with 7 *.

- = F to~~~~~~~~~~~~~-. . d

*!,*-g-bF

20 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 21

ticular island where the specimens were collected is unknown. 2. R. burrus burrus: Trinkut Island in the Nicobars. R. burrus burrescens: Great Nicobar Is- land and Little Nicobar Island. 3. R. simalurensis simalurensis: Pulau Sim- alur and Pulau Siumat, both northwest of Pulau Nias. R. simalurensis lasiae (includes babi): Pu- lau Lasia and Pulau Babi, both southeast of Pulau Simalur. 4. R. lugens lugens: Pulau Pagai Utara and Pulau Pagai Selattan in the Mentawai Islands. R. lugens mentawi: Pulau Sipora and Pu- lau Siberut in the Mentawais. 5. R. adustus: Pulau Enggano, southeast of the Mentawais. Specimens in all samples are oflarge body D size; the tail is about as long or slightly shorter than length of head and body; upperparts range from brown to dark brown and blackish; underparts are white to dark gray and grayish brown; and five pairs ofmammae are positioned as they are in R. rattus mindanensis. The skulls are large and tend to be chunky; the molar rows are long and the teeth

FIG. 15. Crania of adult Rattus tawitawiensis wide. Values from measurements of skull contrasted with the Rattus palmarum Group. A, lengths and toothrow lengths from the sam- R. tawitawiensis (DMNH 3525). B, R. lugens, Pu- ples are contrasted with those of R. tawita- lau Pagi Utara, Mentawais (AMNH 103020). C, wiensis in table 3. Crania are compared in R. simalurensis, Pulau Lasia, Simalur Islands figures 14 and 15, and toothrows in figure 16. (USNM 114255). D, R. burrus, Trinkut Island, We begin our comparisons with samples Nicobars (USNM 11 1804). E, R. palmarum, Ni- from the Nicobars, islands that are separated cobar Islands (NMW B-27). Natural size. Note the from the tip of Sumatra by a channel more deeper braincase of R. tawitawiensis as compared than 700 fathoms deep and from the western to the other crania. margin of the Sunda Shelf by the deep An- daman Sea. Of all the samples provisionally placed in the R. palmarum Group, those from dark pelage. Most resemble the specimens the Nicobars representing R. palmarum and from Tawitawi Island in some way, and all R. burrus are least similar to the three spec- have to be contrasted with R. tawitawiensis imens ofR. tawitawiensis in features ofskins to help define that species. and skulls. The three specimens of R. pal- Whether or not all of the named forms we marum at hand are larger in body size than discuss under the R. palmarum group ac- those of R. tawitawiensis and the skulls and tually belong there will be determined by a molar rows are appreciably longer. Fur cloth- future study now being undertaken (Musser, ing the upperparts ofR. palmarum is brown, ms). Our analyses so far indicate that t-he sam- very coarse and semispinous to the touch, a ples can be grouped into the following five texture produced by the numerous semi-rigid clusters. translucent spines scattered throughout the 1. R. palmarum: Nicobar Islands; the par- coat. The coloration resembles that in R. rat- 22 AMERICAN MUSEUM NOVITATES NO. 2818

TABLE 4 Taxa in the Rattus palmarum Group Taxon Author and Date Type Locality palmarum Zelebor (1869, p. 26) Nicobar Islands burrus Miller (1902, p. 768) Trinkut Island, Nicobars burrescens Miller (1902, p. 771) Great Nicobar Island simalurensis Miller (1903a, p. 458) Pulau Simalur, off coast of West Sumatra lugens Miller (1903b, p. 33) Pulau Pagi Utara, Mentawai Islands lasiae Lyon (1916, p. 446) Pulau Lasia, off west coast of Sumatra babi Lyon (1916, p. 447) Pulau Babi, off west coast of Sumatra mentawi Chasen and Kloss (1927, p. 831) Pulau Sipora, Mentawai Islands adustus Sody (1940, p. 397) Pulau Enggano, off west coast of Sumatra tus mindanensis rather than R. tawitawiensis. with larger sphenopalatine vacuities. The The underparts are whitish gray, paler than similarity to R. tiomanicus suggested by color those in the Tawitawi rat. Female R. pal- and texture of fur is reflected in the skull, marum have two pectoral teats in addition which is reminiscent of a large and robust to the other four pairs; such a pair is absent cranium of R. tiomanicus. The depth of the from specimens of R. tawitawiensis. braincase and narrow incisive foramina seen In addition to being larger than R. tawi- in skulls of R. burrus resemble those features tawiensis, the cranium of R. palmarum is in R. tiomanicus and R. palmarum, not R. more slender; it appears elongate when com- tawitawiensis. pared with the chunky skull of the Tawitawi The foregoing discussion has pointed out rat. The rostrum is longer and thinner, the distinctive differences between R. burrus and prominent postorbital ridging begins farther R. tawitawiensis in coat color and cranial fea- forward, the braincase is not as deep, the in- tures. Characteristics ofthe molars, however, cisive foramina are not as wide, and the are not so different. On average, the molar sphenopalatine vacuities are smaller. rows are shorter in R. burrus than in R. tawi- There are no dental features that suggest a tawiensis, but the occlusal patterns are very close relationship between R. tawitawiensis similar. and R. palmarum. Occlusal patterns of the Specimens from Simalur and nearby is- latter resemble those characteristic of R. rat- lands, the Mentawai Islands, and Pulau Eng- tus mindanensis and not R. tawitawiensis. gano, representing (respectively) R. simalur- Rattus burrus is smaller-bodied than R. ensis, R. lugens, and R. adustus, bear a greater palmarum and more like R. tawitawiensis in resemblance to R. tawitawiensis than to either body size, although when compared with R. palmarum or R. burrus. Among these specimens of the latter, those of R. burrus of samples there are two clusters. Series from comparable age are smaller. Upperparts of the Simalur Island Group form one morpho- R. burrus range from brown to a dark brown logical unit, those from the Mentawais and that tends to be a solid color without the Pulau Enggano the other. The Enggano rat, agouti pattern seen in R. tawitawiensis. Un- R. adustus, is known only by the holotype, derparts of most specimens are white or which is a very young adult. Compared with cream; others have gray and buff suffusions. specimens of comparable age from the Men- The fur on the dorsum and venter is soft, tawais and Simalur islands, it is a much larger much different from that in R. palmarum. animal, as is indicated by length of toothrow The coloration reminds us of that in most (table 3); in all other features of skin and populations of R. tiomanicus from places on skull, R. adustus is most like the series ofrats the Sunda Shelf rather than the color of the from the Mentawai Islands. Rats in all the rats from Tawitawi Island. other samples are like R. tawitawiensis in body The cranium of R. burrus is a smaller and size and proportion. All have long toothrows stockier version ofthat in R. palmarum, but and wide molars that are similar to the dental 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 23 I AA

404*t

;001 4I.-.. I .,...

FIG. 16. Upper molar rows ofRattus tawitawiensis contrasted with members ofthe Rattus palmarum Group. A, R. tawitawiensis (DMNH 3525). B, R. lugens, Pulau Pagi Utara, Mentawais (AMNH 103021). C, R. burrus, Trinkut Island, Nicobars (USNM 111806). D, R. simalurensis, Pulau Simalur (USNM 114224). E, R. palmarum, Nicobars (NMW B-26). Approximately x 10. dimensions of the Tawitawi rat, and there is lugens, and R. adustus but there are conspic- close resemblance in occlusal patterns. uous distinctions in details; these differences All samples contain dark animals in which are similar to those seen between samples of the coat color, agouti pattern, and fur texture R. rattus mindanensis and the Tawitawi an- are similar to that in R. tawitawiensis. The imals. Crania ofthe latter appear more robust primary difference is tone; the three speci- and chunky because the rostrum is wider, the mens of R. tawitawiensis are not as dark as zygomatic arches more flaring, and the brain- the examples of R. simalurensis, R. lugens, case wider and deeper, as can be seen in fig- and R. adustus; the contrast is prominent in ures 14 and 15. Also, the postorbital ridging many of the specimens of R. lugens, which does not extend as far forward in R. tawi- are brownish black on the dorsum. The ven- tawiensis. Aside from the generally wider cra- tral fur of R. tawitawiensis is paler than in nium, the most conspicuous differences most of the other specimens in which the among the samples is the wide incisive fo- color ranges from dark gray to dark grayish ramina in R. tawitawiensis. That feature in brown and buff. In contrast to the examples specimens of R. simalurensis is narrow; ex- of R. tawitawiensis, all females of the three amples ofR. lugens and R. adustus have wid- other species have five pairs ofmammae, not er incisive foramina than do those of R. si- four. malurensis, but not as wide as those in R. In general aspect, skulls ofR. tawitawiensis tawitawiensis. are similar to those of R. simalurensis, R. Even though R. tawitawiensis is more like 24 AMERICAN MUSEUM NOVITATES NO. 2818

.* 4)

1: ..0 ": I

I. 1 , I / ,i1'

,.!e P,

.. ...

i4\t i *, .* * v. 'S de .-.. '' ' _ ._B Cb D vI. FIG. 17. Crania of adult Rattus tawitawiensis compared with Rattus tiomanicus. A, R. tawitawiensis (DMNH 3525). B, R. tiomanicus, Sabah, northern Borneo (USNM 292689). C, R. tiomanicus, Java (AMNH 250114). D, R. tiomanicus, eastern Sumatra (AMNH 106666). Natural size.

rats from the Mentawai and Simalur islands as those native to Borneo and other islands than those on the Nicobars, it still has a dis- on the Sunda Shelf. No species native to the tinctive combination of features which sep- Philippine Islands bears a close morpholog- arates it from R. simalurensis, R. lugens, and ical resemblance to R. tawitawiensis. Of the R. adustus. We have no evidence suggesting two species of Rattus from there, R. everetti that the specimens from Tawitawi Island rep- is larger-bodied and has long, shaggy pelage resent an insular subspecies ofany ofthe pop- and a long, bicolored tail. Its cranial and den- ulations on Pulau Enggano, the Mentawais, tal features (see the illustrations in Musser the Simalur Group, or even the Nicobar Is- and Newcomb, 1983) are unlike those char- lands. acterizing the Tawitawi rat. The other species, OTHER COMPARISONS R. mindorensis, is known to occur only on the island of Mindoro. Its morphology is What other species of Rattus did we ex- closely similar to specimens ofR. tiomanicus amine and why didn't we consider them mor- from the Sunda Shelf (Musser and Califia, phologically close enough to the Tawitawi an- 1982). If there is a species of Rattus living imals for inclusion in this report? Because the on any Philippine island, especially Minda- sample came from the Sulu Archipelago, that nao, which has a morphology similar to that chain of islands forming a broken link be- ofR. tawitawiensis it has yet to be discovered. tween Borneo on the Sunda Shelf and Min- Looking west from the Sulu Archipelago danao in the southern Philippines, we natu- toward the islands and peninsula on the Sun- rally scanned the Philippine murids as well da Shelf, we know of four species of Rattus 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 25

of mammae, R. hoogerwerfi has four; it, like R. tawitawiensis, lacks the pectoral pair. The skulls of R. baluensis and R. hoogerwerfi are gracile and flat compared with the chunky, deep cranium ofR. tawitawiensis; postorbital and temporal ridges are low and inconspicuous in comparison; sides of the braincase are vertical or nearly so, not flaring outward from the temporal ridges as they do in R. tawitawiensis; and the incisive foramina are narrow, not expansive. There are no dental features suggesting that either ofthese species is morphologically close to R. tawitawiensis. Rattus annandalei resembles R. tawitawiensis in body size but little else. The tail is much longer than length of head and body, upperparts are grayish brown, underparts range from white to pale yellow, and females have four pairs of mammae, including one pectoral pair. Rattus annandalei also has narrower and much shorter incisive foramina; a palatal bridge that ends just past posterior margins ofthe third molars, instead ofform- ing a shelfbehind those teeth as in the Tawi-

FiG. 18. Upper molar rows. Left: Rattus tawitawi rat; very small sphenopalatine vacuities, tawiensis (DMNH 3528). Right: Rattus tioman- which are unlike the wide and spacious open- icus, Java (AMNH 250111). Approximately x ings in R. tawitawiensis; and large, somewhat inflated auditory bullae. Occlusal patterns of the molars, especially the uppers, are more native to that region. Rattus baluensis occurs complex than those of R. tawitawiensis (see in the mountains of Sabah (norther Bomeo) fig. 91 in Musser and Newcomb, 1983, p. and Sumatra. Rattus hoogerwerfi is a moun- 518). These arejust a few ofthe many features tain rat of northerm Sumatra. Rattus annan- distinguishing the two species. The overall dalei has been recorded from the Malay Pen- morphology ofR. annandalei suggests that it insula, Singapore, eastern Sumatra, and the is peripheral to the core ofspecies in the genus islands of Padang and Rupat off the coast of Rattus; it certainly has no close morpholog- easter Sumatra (see Musser and Newcomb, ical resemblance to R. tawitawiensis. 1983, for illustrations, measurements, and Rattus tiomanicus is the fourth species na- descriptions of these species). Rattus tic- tive to the peninsula and islands on the Sunda manicus occurs on the Malay Peninsula, Bor- Shelf. It is smaller in body size than R. tawi- neo, Sumatra, Java, Bali, many smaller is- tawiensis, although more similar than the lands on the Shelf, and two places off of the three other native Sundanese Rattus. Upper- Shelf: the Maratua Archipelago and Pulau parts are brown or tawny in most samples of Enggano (Musser and Califia, 1982). R. tiomanicus; underparts range from white Morphologies of three of these species are to grayish white. Samples from some places, unlike that of R. tawitawiensis. Rattus ba- such as Pulau Nias and the Maratua Archi- luensis and R. hoogerwerfi are smaller-bod- pelago, are much darker and represent one ied.' Both have thick, long fur that is tawny extreme in color variation: the dorsum is or chocolate brown on the dorsum and buffy blackish brown or chestnut and the venter is gray or deep ochraceous on the venter. Both dark buffy gray (Musser and Califia, 1982). have tails that are much longer than length The tail ofR. tiomanicus is monocolored and ofhead and body; the distal halfin R. hooger- averages slightly longer than combined werfi is white. Rattus baluensis has five pairs lengths ofhead and body. The feet are brown. 26 AMERICAN MUSEUM NOVITATES NO. 2818

Pelage is soft and sleek with short guard hairs; some islands beyond the Sunda Shelfthan to its texture is similar to that in R. tawita- any species living on the islands and penin- wiensis. Females have five pairs of mammae sula ofthe Shelf. Ofthese insular populations, positioned as they are in R. rattus. The darkly the Tawitawi rat bears a general morpholog- pigmented populations of R. tiomanicus re- ical resemblance to R. tiomanicus mara from semble the three specimens of R. tawita- the Maratua Archipelago, but the tie involves wiensis, but the paler samples contrast sharp- coloration and habitation of oceanic islands; ly with the Tawitawi animal. Rattus beyond these points, R. tawitawiensis is no tawitawiensis also differs from R. tiomanicus more closely related to the Maratua popu- in its shorter tail relative to length of head lation than to R. tiomanicus from mainland and body and only four pairs of mammae. Borneo and other islands on the Sunda Shelf. Except for its much smaller size, the skull The Tawitawi rat shares oceanic insular of R. tiomanicus closely resembles that of R. endemism, large body size, short tail, and tawitawiensis (table 3, fig. 17). The latter is four pairs ofmammae (with the pectoral pair chunkier in overall configuration, has a rel- absent) with Rattus stoicus, known only to atively wider incisive foramina, and has a inhabit the Andaman Islands west ofthe Sun- deeper braincase with outwardly sloping da Shelf. However, no other features provide rather than nearly vertical sides. Molar cusp a tight link between the species. patterns are similar in the two species (fig. Specimens from the Nicobar Islands, Pu- 18). Other than size (table 3), there is really lau Simalur and nearby islands, the Menta- no obvious feature that will distinguish them. wai Islands, and Pulau Enggano have a closer We did not confine our investigation to morphological similarity to R. tawitawiensis comparing the Tawitawi sample with sam- than does R. stoicus. The dark coloration and ples of Rattus from the Sunda Shelf and the relatively wide incisive foramina ofR. lugens Philippines only. We also examined groups from the Mentawai Islands are especially of Rattus from east of the Shelf in Australia, reminiscent of R. tawitawiensis. Even more New Guinea, and the Moluccas; those from similar to R. tawitawiensis is R. hoffmanni Pulau Enggano, Christmas Island, and Su- from Sulawesi. Although smaller in body size lawesi that are not part of the R. palmarum and usually paler in color, the Sulawesian rat Group; and species from continental South- shares pelage texture and pattern, number of east Asia north of the Isthmus of Kra (see mammae (which includes no pectoral pairs), Musser and Newcomb, 1983, p. 572, for a extent of supraorbital ridging, and general list of native Rattus). We did not neglect cranial configuration with the Tawitawi an- subfossil remains ofSundanese Rattus or the imal. specimen of R. trinilensis from the Middle Resolution of relationships beyond this Pleistocene of Java (Musser, 1982b) in our general picture is not posssible at present. comparisons. In the end, we could not detect The sample of Rattus tawitawiensis is too close morphological resemblance between R. small. Our evidence points to a closer mor- tawitawiensis and any of the species in these phological relationship between R. tawita- other groups of Rattus. wiensis and populations ofR. hoffmanni from Sulawesi and most ofthe R. palmarum Group CONCLUSION than to any other species of Rattus. Study of Morphological evidence gathered from larger series from the Sulu Archipelago will skins and skulls supports the hypothesis that be necessary to refine this outline. the three specimens of large-bodied, short- What is significant to us is that the native tailed, and dark-colored Rattus from Tawi- Tawitawi Rattus seems part of a pattern. It tawi Island represent a biological species dis- and populations ofRattus from Sulawesi, Pu- tinguished from any other species of Rattus lau Enggano, the Mentawai and Simalur is- by the combination of characters presented lands, the Nicobars, and possibly the An- in the diagnosis of R. tawitawiensis. daman Islands appear to be more closely The evidence is also consistent with the related to one another than to any species hypothesis that R. tawitawiensis is more known to occur on the islands and peninsula closely related to species of Rattus native to of the Sunda Shelf or on continental South- 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 27 east Asia. Furthermore, aside from R. hoff- to Cambodia and Vietnam. Rattus sikkimen- manni, there is no other native Sulawesian sis also occurs on four islands in the South Rattus and no species from the Philippine China Sea near and south of the Isthmus of Islands that has a morphology consistent with Kra. These are numbered 46 to 49 on the the pattern. map of figure 19 and and are, respectively, What we know ofthese insular Rattus sug- Koh Tau, Koh Pangan, Koh Samui, and Koh gests that each population has its own dis- Kra. The population on Koh Samui was re- tinctive morphological features and that each garded as a distinctive species, R. remotus, may have been derived from populations that by Marshall (1977). It wasn't until Musser once occurred on the Sunda Shelfbut are not (Ms) plotted the geographic distribution ofR. present there now. The only species now na- sikkimensis and studied the island samples tive to the large and small islands ofthe Shelf, that it became apparent that remotus was as well as the Malay Peninsula, that has a really an insular population of R. sikkimen- morphology similar to those of the rats on sis. That species has not been recorded from islands beyond margins ofthe Shelfis Rattus the nearby peninsula. Therefore, populations tiomanicus. Whether that species is more on the four islands are more closely related closely related to the insular oceanic species to each other than to any species of Rattus or to Asian R. rattus and its allies has yet to now known from the adjacent peninsular be determined. Except for the population of mainland. large-bodied, dark rats in the Maratua Ar- A variant of the pattern is formed by the chipelago, the morphological evidence sup- relationships between populations of rats on ports the hypothesis that R. tiomanicus may island groups next to one another. Rattus be genetically isolated from populations of mindorensis is a good example. This species the dark and large-bodied rats from the Sulu has always been regarded as part of the Phil- Archipelago, Sulawesi, Pulau Enggano, the ippine Island fauna. However, it is found no- Mentawai and Simalur islands, the Nicobars, where in the Philippines outside of Mindoro and the Andaman Islands. We know this is and has no close relative on any other Phil- true on Pulau Enggano because both R. tio- ippine Island. In features of skin, skull, and manicus and R. adustus inhabit that island. teeth, it is closely similar to samples ofRattus We are analyzing the relationships between tiomanicus of the Sunda Shelf, and Musser R. tiomanicus and samples of Rattus from and Califia (1982, pp. 26-27) hypothesized the oceanic islands mentioned above and our that it represented an insular form of R. tio- results will be presented in another report. manicus. The latter has representatives on The picture of possible relationships be- the oceanic islands of Enggano, the Maratua tween R. tawitawiensis and species from oth- Archipelago, and, according to Musser and er islands is a pattern we frequently encounter Califia), "Mindoro, relative to the northeast in the Malayan region. Populations on is- segment of the Sunda Shelf, may be just lands may be closely related to those on an another island off ofthe Shelfand east of the adjacent mainland. Some insular popula- 100 fathom line that was reached by a pop- tions, however, have no close relatives on the ulation of what is recognized as R. tioman- nearby mainland; instead they tie to popu- icus on islands of the Shelf." lations on other islands. Rattus tawitawien- We return to the Tawitawi rat. We know sis, for example, appears to be more closely something of its distinctive morphology and allied to populations ofRattus on islands sit- we have formulated an hypothesis about its uated beyond margins ofthe Sunda Shelfthan relationship to other species ofRattus. There to any other population of the genus, and it is much we do not know. We are ignorant of has no close relative on the adjacent Bornean its natural history and we do not know the mainland. A similar situation is seen in the extent of its geographic range. Rattus tawi- distribution of Rattus sikkimensis on islands tawiensis may have a larger distribution than that are a part of the Sunda Shelf. The dis- is indicated by our sample from one island. tribution ofthat species is shown in figure 19. Tawitawi Island is the southwestern segment It is primarily Indochinese, extending from of a submerged ridge that extends northeast Nepal east through southern China and south to form Jolo Island. The sea is less than 45 28 AMERICAN MUSEUM NOVITATES NO. 2818

FIG. 19. Geographic distribution ofRattus sikkimensis. In addition to the mainland and the offshore islands of Hong Kong (locality 3), Hainan (localities 4 and 5), and Koh KIum (locality 45), the species also occurs on four islands in the South China sea opposite the Malay Peninsula: Koh Tau, Koh Pangan, Koh Samui, and Koh Kra (localities 46 to 49, respectively). See text for further discussion. m deep over this ridge. During late Pleisto- suitable habitat is present now and also ex- cene, when sea level has been estimated to isted when Jolo was part of the larger land have dropped 100 to 120 m below present area embracing Tawitawi. level (Chappell and Thom, 1977; Gascoyne, How and when Rattus tawitawiensis got to Benjamin, and Schwarcz, 1979; Bloom, Tawitawi Island are both mysteries. The large 1983), Tawitawi and Jolo would have been Philippine island ofMindanao to the east and part ofthe much larger island shown in figure Borneo to the west bracket the Tawitawi-Jolo 1. During middle Pleistocene, when sea level group ofislands. Jolo is separated from Min- was probably 160 to 180 m lower than at danao by a deep channel and deep waters present (Donn, Farrand, and Ewing, 1962; isolate Tawitawi from Borneo. During mid- Gascoyne, Benjamin, and Schwarcz, 1979), dle or late Pleistocene when sea levels were the island would have been even larger. As- lower than at present, there is no evidence suming populations of R. tawitawiensis were that the larger land area of Tawitawi-Jolo present on Tawitawi during late or middle would have been connected to either Min- Pleistocene times, we would expect to find it danao or Borneo. There is no way that these now on other islands between Tawitawi and connections could have occurred without a Jolo, and certainly on Jolo, provided that fair dose of either tectonics or magic. The 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 29

TABLE 5 Mammals from the Sulu Archipelago Island Sanga Genus and Species Sibutu Simunul Bongao Sanga Tawitawi Jolo Shrews Crocidura edwardsianaa T Bats Acerodon jubatus x x x x Cynopterus brachyotis x x x x x Eonycteris spelaea _ X - Ptenochirusjagori x x Pteropus hypomelanus T Pteropus pumilus x x x Pteropus speciosus x x x Rousettus amplexicaudatus x x x x x Rhinolophus virgo T

Rhinolophus sp. x - - ~~x Kerivoula pellucida T Miniopterus sp. x X - Myotis macrotarsus _ _ T Primates Nycticebus coucang - X G X TB - _ _ _ Macaca fascicularis - T Rodents Mus castaneus x Rattus exulans x T Rattus rattus mindanensis x x x x x Rattus tawitawiensisa x Carnivores Paradoxurus hermaphroditus T x _ Pigs Sus barbatus - - - - Gr Deer Cervus nippon GG a Endemic to the Sulu Archipelago. Abbreviations: T = Taylor, 1934; TB = Timm and Bimey, 1980; G = Groves, 1971; Gr = Groves, 1981; GG = Grubb and Groves, 1983; X = specimens in the Delaware Museum of Natural History. presence of an endemic species of Rattus on has considered this topic previously, we will Tawitawi likely represents the past dispersal do so here briefly. of a founding population from either Min- The available records of mammals from danao or what is now Borneo, perhaps at a the Sulu Islands are summarized in table 5. time in the past when sea levels were lower Most of these records are from specimens in than they are now and land areas closer to the Delaware Museum of Natural History. one another. Thirteen of the 23 species are bats. Four of One possible source ofinformation regard- the bats are Philippine endemics; the others ing the origin of R. tawitawiensis is the zoo- are widespread in Southeast Asia, including geography of the mammalian fauna of the the Philippines. Ofthe 10 non-volant species, Sulu Archipelago as a whole. Because no one three are introduced commensals (Rattus ex- 30 AMERICAN MUSEUM NOVITATES NO. 2818 ulans, R. rattus mindanensis, and Mus cas- currence ofRattus on the Shelfis not a Recent taneus), four are widespread in Southeast Asia event because a species of that genus, or a (Macacafascicularis, Paradoxurus hermaph- related genus with similar dental and man- roditus, Sus barbatus, and Cervus nippon), dibular morphology, was present during mid- two are endemic to the Sulus (Crocidura ed- dle Pleistocene in what is now the Trinil re- wardsiana and Rattus tawitawiensis), and one gion of Java (Musser, 1982b). That species, is otherwise found only on the Sunda Shelf R. trinilensis, is not part of the fauna now (Nycticebus coucang). The depauperate na- living in the Sunda region. We wonder what ture ofthe non-volant fauna is similar to that other species ofRattus may have been on the of oceanic islands in the Philippines (Cami- Sunda Shelfin the -past when Sundaland con- guin Island, for example; Heaney, 1984), ex- sisted of islands and peninsula during times cept for the presence of the two endemic of high sea levels and a large continental ex- species. None of the species characteristic of panse above water at times oflower sea levels. the southern Philippines is known to occur Perhaps an ancestral species occurred there in the Sulus, even though such species (for that is absent from the Recent fauna and now example, Cynocephalus volans, Exilisciurus represented by R. stoicus in the Andaman concinnus, and the Sundasciurus philippi- Islands, R. palmarum and R. burrus in the nensis group) occur on Basilan, and C. volans Nicobars, R. simalurensis in the Simalur Is- is known from the small islands ofthe Tonkil lands, R. lugens in the Mentawais, R. adustus Group between Basilan and Jolo, at the edge on Pulau Enggano, R. hoffmanni on Sula- of the 120 m bathymetric line around Min- wesi, and R. tawitawiensis in the Sulu Ar- danao (Taylor, 1934). Nycticebus coucang is chipelago. the only member of the Bornean fauna that We close with an alternative notion that occurs on the Sulus, and it is sufficiently pop- should be tested with data from a larger series ular as a pet that it may have been introduced. of R. tawitawiensis than is now available. The bat fauna is similar to that found on Judged by our three specimens of the Sulu many small islands in the southern Philip- rat, the species has close morphological sim- pines, both oceanic and Mindanao land- ilarity with R. hoffmanni from Sulawesi. bridge in origin. There is no evidence of a Could that large island have been the source close relationship to Borneo. ofthe Tawitawi animal, or does the similarity We believe that these data (presence oftwo between the two species represent derivation endemic species ofnon-volant mammals, ab- from an ancestral population that was present sence of characteristic members of the Bor- on what is now Borneo and dispersal to the nean or Mindanao faunas) are consistent with Sulu Archipelago and Sulawesi? the geological data in indicating that there were no continuous land-bridge connections LITERATURE CITED to either Borneo or Mindanao during the late Pleistocene. Thus, dispersal of the ancestor Bloom, Arthur L. 1983. Sea level and coastal morphology ofthe of R. tawitawiensis over a narrow salt-water United States through the Late Wiscon- channel is indicated. sin glacial maximum. In H. E. Wright, We look toward Borneo and the Sunda Shelf Jr. (ed.), Late-Quarternary environ- for that dispersal source. We know of no ments of the United States, vol. 1, The species of Rattus now living on Mindanao Late Pleistocene, Stephen C. Porter (ed.). that is closely related to R. tawitawiensis. On Minneapolis, Univ. Minnesota Press. the other hand, of several species of Rattus Chappell, J., and B. G. Thom native to the Sunda Shelf(to the west ofTaw- 1977. Sea levels and coasts. Pp. 275-291, figs. itawi Island), R. tiomanicus is similar to R. 1-3. In J. Allen, J. Golson, and R. Jones tawitawiensis in of its mor- (eds.), Sunda and Sahul. Prehistoric many aspects studies in Southeast Asia, Melanesia and phology. We have also suggested that R. taw- Australia. London, Academic Press. itawiensis is closely related to species ofRat- Chasen, F. N., and C. Boden Kloss tus inhabiting oceanic islands that rim the 1927. 41. Spolia Mentawiensia.-Mammals. margin of the Shelf; likely the Shelf was the Proc. Zool. Soc. London, no. LIII, pp. source for these insular populations. The oc- 797-840, pls. I-V, 1 map. 1985 MUSSER AND HEANEY: NEW SPECIES OF RATTUS 31

Donn, William L., William R. Farrand, and Mau- Miller, Gerrit S., Jr. rice Ewing 1902. The mammals ofthe Andaman and Ni- 1962. Pleistocene ice volumes and sea-level cobar Islands. Proc. U.S. Natl. Mus., lowering. Jour. Geol., vol. 70, no. 2, pp. vol. 24, pp. 751-795, pls. XLI-XLII. 206-214, figs. 1-3. 1903a. Mammals collected by Dr. W. L. Ab- duPont, John E., and Dioscoro S. Rabor bott on the coast and islands of north- 1973. South Sulu Archipelago birds. An ex- west Sumatra. Ibid., vol. 26, pp. 437- pedition report. Occas. Papers Dela- 484, pls. 1-2, 1 map. ware Mus. Nat. Hist., no. 9, pp. 1-63, 1903b. Seventy new Malayan mammals. figs. 1-2. Smithsonian Misc. Coll., vol. 45, pts. 1 Gascoyne, M., G. J. Benjamin, and H. P. Schwarcz and 2, pp. 1-73, pls. 1-19. 1979. Sea-level lowering during the Illinoian Musser, Guy G. glaciation: evidence from a Bahama 1970. Species-limits of Rattus brahma, a mu- "Blue Hole." Science, vol. 205, no. 4408, rid rodent of northeastern India and pp. 806-808, 1 fig. northern Burma. Amer. Mus. Novi- Groves, Colin P. tates, no. 2406, pp. 1-27, figs. 1-6. 1971. Systematics ofthe genus Nycticebus, pp. 1973. Zoogeographical significance ofthe rice- 44-53, figs. 1-3. In Proc. 3rd Int. Congr. field rat, Rattus argentiventer, on Ce- Primat., Zurich, 1970, vol. 1. Basel, lebes and New Guinea and the identity Karger. ofRattus pesticulus. Ibid., no. 2511, pp. 1981. Ancestors for the pigs: taxonomy and 1-30, figs. 1-5. phylogeny of the genus Sus. Tech. Bull. 1977. Epimyx benguetensis, a composite, and No. 3, Dept. Prehist., Res. School Pa- one zoogeographic view ofrat and mouse cific Stud., Australian Nat. Univ., pp. faunas in the Philippines and Celebes. i-iii + 1-96, figs. 1-14, pls. 1-9. Ibid., no. 2624, pp. 1-15, figs. 1-4. Grubb, Peter, and Colin P. Groves 1982a. Results of the Archbold Expeditions. 1983. Notes on the taxonomy of the deer No. 108. The definition of Apomys, a (Mammalia, Cervidae) of the Philip- native rat ofthe Philippine Islands. Ibid., pines. Jena, Zool. Anz., 2 10/2, pp. 119- no. 2746, pp. 1-43, figs. 1-19. 144, 1 fig. 1982b. The Trinil rats. Pp. 65-85, pls. 1-8. In Heaney, Lawrence R. G. J. Bartstra and W. A. Casperie (eds.), 1984. Mammals from Camiguin Island, Phil- Modern quarternary research in South- ippines. Proc. Biol. Soc. Wash., vol. 97, east Asia, vol. 7. Rotterdam, A. A. Bal- no. 1, pp. 119-125. kema. King, P. B., and E. M. McKee 1984. Identities ofsubfossil rats from caves in 1949. Terrain diagrams of the Philippine Is- southeastern Sulawesi. Pp. 61-94, pls. lands. Bull. Geol. Soc. Amer., vol. 60, 1-12. Ibid., vol. 8. Rotterdam, A. A. pp. 1829-1836, 1 fig., 5 pls. Balkema. Lyon, Marcus Ward, Jr. Musser, Guy G., and Debra Califia 1916. Mammals collected by Dr. W. L. Ab- 1982. Results of the Archbold Expeditions. bott on the chain ofislands lying offthe No. 106. Identities of rats from Pulau western coast ofSumatra, with descrip- Maratua and other islands of East Bor- tions of twenty-eight new species and neo. Amer. Mus. Novitates, no. 2726, subspecies. Proc. U.S. Natl. Mus., vol. pp. 1-30, figs. 1-5. 52, pp. 437-462. Musser, Guy G., and Cameron Newcomb Marshall, Joe T., Jr. 1983. Malaysian murids and the Giant Rat of 1977. Family Muridae: rats and mice. Pp. 396- Sumatra. Bull. Amer. Mus. Nat. Hist., 487. Reprinted in Mammals of Thai- vol. 174, art. 4, pp. 327-598, figs. 1- land [Boonsong Lekagul and J. A. 117. McNeely (eds.)]. Bangkok, Thailand, Sody, H. J. V. Assoc. Conserv. of Wildlife. 1940. On the mammals of Enggano. Treubia, Medway, Lord vol. 17, pp. 391-401, 1 map. 1977. Mammals of Borneo. Field keys and an Taylor, Edward H. annotated checklist. Monographs ofthe 1934. Philippine land mammals. Monograph Malaysian Branch of the Royal Asiatic Bur. Sci. (Manila), no. 30, pp. 1-548, Society, no. 7, Kuala Lumpur, Perche- figs. 1-12, pls. 1-25. takan Mas Sdn. Bhd., pp. xii-1 72, figs. Thomas, Oldfield 1-11, pls. 1-24. 1907. A subdivision ofthe old genus Nesokia, 32 AMERICAN MUSEUM NOVITATES NO. 2818

with descriptions ofthree new members Zelebor, Johann of the group, and of a Mus from the 1869. Reise der osterreichischen Fregatte No- Andamans. Ann. Mag. Nat. Hist., vol. vara um die Erde in den Jahren 1857, 20, ser. 7, pp. 202-207. 1858, 1859. Zoologischer Theil. (Wir- Timm, Robert M., and Elmer C. Birney belthiere.) 1. Saugethiere. Pp. 1-42, pls. 1980. Mammals collected by the Menage Sci- 1-3, Wien. entific Expedition to the Philippine Is- lands and Borneo, 1890-1893. Jour. Mammal., vol. 61, no. 3, pp. 566-571.