Bunomys coelestis ( Thomas, 1896 )

Musser, Guy G., 2014, A Systematic Review Of Sulawesi Bunomys (Muridae, Murinae) With The Description Of Two New Species, Bulletin of the American Museum of Natural History 2014 (392), pp. 1-313 : 106-116

Bunomys coelestis ( Thomas, 1896)

Mus coelestis Thomas, 1896: 248 .

Fourteen years after naming and describing Mus coelestis, Thomas (1910) used it as the type species for the genus Bunomys . In the years to follow, coelestis was shuttled between Bunomys and Rattus (table 4): it was retained in Bunomys by Tate (1936), later transfered to subgenus Rattus of Rattus ( Ellerman, 1941, 1949; Laurie and Hill, 1954), placed in subgenus Bullimus of Rattus ( Misonne, 1969) , returned to Bunomys in the early 1980’s ( Musser, 1981b; Musser and

TABLE 29 Results of Principal-Components Analysis of Bunomys chrysocomus and B. coelestis The sample of B. coelestis from Gunung Lompobatang (southwestern peninsula), B. chrysocomus from Sadaunta (west-central region), and two subfossils from Ulu Leang I (southwestern peninsula) are compared. Upper graph: AMNH 266975 is the subfossil (m2 is missing). Lower graph: AMNH 269954 is the subfossil (clm1–3 could not be measured). Correlations (loadings) of four dental log-transformed variables are based on 41 specimens; see figure 34.

Newcomb, 1983), and eventually renewed as a distinct species of Bunomys endemic to Gunung Lompobatang on the southwest peninsula of Sulawesi ( Corbet and Hill, 1992; Musser, 1991; Musser and Holden, 1991; Musser and Carleton, 1993, 2005).

HOLOTYPE: BMNH 97.1 .3.12, the skin and skull of an old adult female collected sometime during October, 1895, by A.H. Everett. Measurements (external, cranial, and dental) and other relevant data are listed in table 18. The skin, a conventional museum preparation, is intact and the pelage coloration is not noticeably altered. The cranium and mandible are whole, all incisors and molars are present.

TYPE LOCALITY: ‘‘ Piek van Bonthain’ ’ (the volcano, Gunung Lompobatang [see fig. 1], 05 ° 20 9 S, 119 ° 55 9 E), 6000 ft (1830 m; locality 1 in the gazetteer and map in fig. 22), southwestern arm of the island, Propinsi Sulawesi Selatan, Indonesia ( caelestis means ‘‘belonging to heaven or of the sky/skies,’’ and presumably Thomas was referring to the high collection site on the flank of Gunung Lompobatang) .

EMENDED DIAGNOSIS: A montane member of Bunomys with long, dark brown fur that among species of Bunomys is morpho- logically most similar to B. chrysocomus , but is distinguished from it by the following traits: (1) longer head and body, tail, and hind feet, longer claws on the front feet; (2) darker brown upperparts, brownish gray underparts; (3) dorsal coat averages longer (18–22 mm; lowland samples of B. chrysocomus have a shorter coat [12–15 mm], those from middle elevations and mountains have slightly longer coats [15–20 mm]) with more of a woolly texture (smooth and silky in B. chrysocomus ); (4) most specimens with a bicolor tail, brown over the dorsal surface and unpigmented ventral surface from base to tip (the range extends from monocolor brown through various degrees of ventral speckling and mottling to bicolored in B. chrysocomus ), and all specimens in the sample lack white tail tips (of the 393 B. chrysocomus surveyed, 77 [20 %] have a white tip); (5) average larger cranium with an appreciably longer rostrum, longer and narrower incisive foramen, longer diastema, wider zygomatic plate, and higher braincase; (6) more elongate dentary and longer, more slender lower incisors; (7) cranial and dental proportional distinctions that are mirrored in the scatter plots derived from multivariate analyses; (8) cusp t3 present on second upper molar in 89 % of sample (only in 17 % of sample of B. chrysocomus ); (9) anterior labial cusplets absent from first lower molar of all specimens examined (present in half the sample of B. chrysocomus ); and (10) anterior labial cusp typically present on second lower molar but infrequent on third lower molar (present in 25 % of the sample; found in the third molars in 65 % of the sample of B. chrysocomus ).

GEOGRAPHIC AND ELEVATIONAL DISTRI- BUTIONS: All material of B. coelestis preserved in collections of museums was obtained at sites between 1800 and 2500 m on Gunung Lompobatang, and the species is likely restricted to montane rainforest formations there. Support for this supposition comes from collections made on the volcano in 1931 by G. Heinrich. He obtained 28 of the 30 documented specimens of B. coelestis in montane evergreen forest between 2000 and 2500 m. Heinrich also had a lower camp at Lombasang (05 ° 16 9 S, 119 ° 55 9 E), 1100 m, in the northwestern foothills of Gunung Lom- pobatang (see the maps in Heinrich, 1932, and Stresemann, 1940) where he trapped a large sample of B. andrewsi but no B. coelestis ; Biror, which is near Lombasang, is the site of a more recent survey that yielded one example of B. andrewsi . Lowland tropical evergreen rainforest usually occurs at that elevation and constitutes the formation from which nearly all samples of B. andrewsi have been collected. Bunomys coelestis seems to be a montane species endemic to Gunung Lompobatang, the only highland massif with appreciable height on the southwestern peninsula of the island, but how low it once occurred will probably never be known. Except for steep slopes at 1000 m, former

TABLE 30 Results of Principal-Components Analysis of Bunomys andrewsi and B. chrysocomus Comparisons are among the sample of B. andrewsi from Lombasang (southwestern peninsula), B. chrysocomus from Sadaunta (west-central region), two subfossils from Ulu Leang I, and one subfossil from Batu Ejaya II (southwestern peninsula). Upper graph: AMNH 266975 is the subfossil from Ulu Leang I (m2 is missing). Lower graph: AMNH 269954 is the other subfossil from Ulu Leang I (clm1–3 could not be measured). AMNH 265013 is the subfossil from Batu Ejaya II and is compared in both ordinations. Correlations (loadings) of four dental log-transformed variables are based on 39 specimens; see figure 35.

forest cover has been converted to farms and tree plantations below about 1700 m ( Fraser and Henson, 1996), and the upper forested slopes of the volcano form an island ‘‘in a sea of densely-populated agricultural land east of Ujung Pandang’’ ( Whitten et al., 1987: 519). The only lowland records of Bunomys from the southwestern peninsula consist of subfossil fragments I identify as B. andrewsi and B. chrysocomus (see those accounts) found in cave sediments near sea level. Except for the sites at Lombasang and Biror, no extant specimens of any species of Bunomys are known from altitudes between 1100 m and sea level, a zone now mostly deforested. Unless archaeological or fossil remains are discovered within this interval, the upper altitudinal limits of B. chrysocomus and the actual lower boundary of its close montane relative, B. coelestis will remain unclear.

SYMPATRY WITH OTHER BUNOMYS: No other species of Bunomys has ever been collected within the elevational range on Gunung Lompobatang in which B. coelestis is documented by specimens (table 4). Samples of B. chrysocomus and B. andrewsi come from lower elevations either on the volcano or elsewhere on the southwestern peninsula (see those two accounts of species).

DESCRIPTION: Here is Thomas’s (1896: 248) original description of Mus coelestis :

Size rather less than Mus fratrorum . Fur long and soft, hairs of back about 18 millim. in length; no longer bristles intermixed. Muzzle unusually long, cylindrical. Eyes small. Ears large, rounded, laid forward in a spirit-specimen they reach to the anterior canthus of the eye. Palate-ridges 3–5. General colour above rich rufous brown (perhaps, in a bright light, nearest to Ridgway’s ‘hazel’), the hairs dark slate for the greater part of their length and just tipped with rufous. The belly is also of much the same colour, only lighter, and the line of demarcation on sides is quite imperceptible. Fore feet with the dark colour extending on to the metacarpals, fingers white; claws exceptionally long and strong, little curved, quite different to those of ordinary rats. Hind feet similarly coloured to the fore; claws long and strong; fifth hind toe without claw reaching to the end of the first phalanx of the fourth; pads, as usual, six in number, large and rounded. Mammae 0–2 5 4; clitoris very long and slender. Tail about equal in length to the head and body, finely scaled (about 14 scales to the centimetre), uniformly thinly haired, blackish above, white below, the two colours intergrading on the sides. Skull less different from that of ordinary rats than the very peculiar external characters would lead one to expect. Muzzle long and cylindrical, slightly concave upwards near the middle of the nasals. Interorbital region very broad, rounded above, its edges slightly beaded. Interparietal narrow antero-posteriorly. Projection of anterior zygoma-root medium. Anterior palatal foramina about the length of the molar series, and narrow, little open, not reaching backwards nearly to the level of [first upper molar]. Bullae small.

Thomas aptly captured the essence of B. coelestis . It has a compact body, long muzzle, dark and thick fur, tail slightly shorter than the combined length of head and body, long front claws, and is one of the physically smaller species of Bunomys (LHB 5 147– 179 mm, LT 5 136–165 mm, LHF 5 35– 39 mm, LE 5 21–25 mm, ONL 5 37.6– 41.8 mm), more similar in size to B. chrysocomus rather than the larger B. prolatus or B. torajae , n. sp. (table 19). The dorsal coat is very long (18–25 over the back), soft to the touch, and woolly in appearance. It is a rich dark brown highlighted by buffy speckling (produced by the combination of dark brown and buffy bands of the overhairs) over most of the head and body; sides of the body are slightly paler. Because guard hairs and overhairs are about the same length, the surface of the coat is smooth.

Fur covering the underparts of the head and body is also long (8–15) and soft. Dark grayish white pelage predominates in the sample, which characterizes 17 of the 27 adults in AMNH. Four have dark grayishwhite coats tinged with buff (tips of the hairs are unpigmented or pale buff), and six express a rich buffy dark gray or ochraceous-gray ventral fur; the contrast between upperparts and underparts is evident but not sharply marked.

The ears (external pinnae) appear naked, but are scantily covered by short hairs. The dried ears on the stuffed museum skins are dark brown (I have not seen freshly caught animals).

Typically, the tail is slightly shorter than the combined length of head and body (LT/ LHB 5 95 %). Of the 30 specimens (adults and juveniles) stored in AMNH, 28 have sharply bicolored tails (as does the holotype): dorsal surface of the tail, from its base to its tip, is dark brown ; the ventral surface, from base to tip, is unpigmented (white). In two specimens, the ventral surface is speckled brown (both scales and hairs are brown). None of the specimens exhibit a white tail tip.

Tarsal and metatarsal surfaces are typically brown and covered by unpigmented (silvery) hairs, all digits are white. The front claws are long and sharp, their lengths relative to lengths of the front digits exceeded only by the elongate claws of B. prolatus (fig. 36), and are not concealed by the short ungual tufts; comparable tufts of silvery hairs sparsely cover the hind claws. Palmar and plantar surfaces are typically unpigmented except for gray near the heel.

Females exhibit the number of teats usual for all species of Bunomys (four, arranged in two inguinal pairs). Testes are likely large relative to body size, as in the close relative B. chrysocomus (table 9), but I have not seen fluid-preserved material to verify this possible proportion in B. coelestis .

Juveniles have soft and woolly dorsal pelage that is darker brown than the adult coat and slightly shorter (overhairs reach 18 mm). Underparts are dark grayish white. Coloration of the ears and feet match those of adults, and the tail is bicolored (dark brown on the dorsal surface, white along the ventral surface) and without a white tip.

The gracile skull is marked by a long rostrum, moderately wide interorbit, and deep braincase; each dentary is elongate, particularly that part of the ramus between incisor and first molar (figs. 37–39). Molars are smaller relative to size of cranium and mandible than is typical of B. chrysocomus , but the basic occlusal patterns formed by cusp rows are similar in the two species (compare the occlusal views of molar rows from B. chrysocomus in fig. 12 with those of B. coelestis in fig. 40); the primary distinction between the two species lies in different frequencies of certain cusps and cusplets, as I describe below.

KARYOTYPE: Not yet determined.

COMPARISONS: Among species of Bunomys , the montane B. coelestis is phenetically most similar to B. chrysocomus in traits associated with skins, skulls, and dentitions. While the two species bear a general resemblance to each other in body size and coat color, there are conspicuous differences between them. Compared with all samples of B. chrysocomus I examined, B. coelestis typically has a longer head and body, tail, and hind foot (table 19), and darker and longer fur (mean 5 20.1 mm, range 5 18– 23 mm, for 23 adult B. coelestis ; mean 5 15.5, range 5 13–18 mm in 41 adult B. chrysocomus from Sungai Sadaunta, 675 m). Bunomys coelestis has a darker brown dorsal coat that appears somewhat woolly in texture (dark brown with buff and gray highlights in B. chrysocomus , and sleek, silky fur), underparts are dark grayish brown (the range is grayish white to gray tinged or washed with pale or rich buff in most examples of B. chrysocomus ). All individuals of B. coelestis lack a white tail tip (20 % of the 396 B. chrysocomus surveyed exhibit a white tip; table 8); most have bicolored tails, brown along the dorsal surface, white ventrally from base to tip (in B. chrysocomus , tails range from bicolor to monocolor brown with intermediate patterns consisting of brown above and white below patterned by a range of mottling or speckling); and have appreciably longer claws on the four digits of each front foot than do specimens of B. chrysocomus (fig. 36).

Differences in absolute size and proportions of cranial and dental dimensions provide noticeable contrasts between B. coelestis and B. chrysocomus , which is evi- denced by illustrations of skulls (figs 37–39), univariate summary statistics (table 31), and results of multivariate analyses. Specimen scores projected on first and second principal components form two parallel elliptical clouds, one identifying specimens of B. chrysocomus , the other representing B. coelestis (fig. 42, upper graph). Axes of these clusters are phenetically distinct: their Yintercepts are significantly different between the two species (‾ 0.189 versus +2.746; F 5 10.94, P 5 0.001), but not their slopes (‾ 0.279 versus ‾ 0.255; F 5 0.47, P 5 0.384). The spread of scores along the first axis is influenced by the positive and moderate to high loadings for cranial variables that highlight the overall larger skull of B. coelestis (indexed by occipitonasal length and zygomatic breadth); its longer facial skeleton (lengths of rostrum, diastema, incisive foramina, and bony palate) and postpalatal region; wider zygomatic plate, rostrum, bony palate, and incisive foramina; wider and deeper braincase, and larger bulla (r 5 0.24–0.86; table 32) compared with the bulk of specimens forming the sample of B. chrysocomus .

Dispersion of scores along the second axis and the moderate to high positive and negative correlations (table 32) point to the relatively higher braincase, longer diastema and incisive foramina, but more slender anterior cranial region of B. coelestis (indexed by breadths of rostrum, bony palate, mesopterygoid fossa, and incisive foramina), and weaker molars (shorter molar rows and narrower molars) compared to those variables in most examples of B. chrysocomus .

Specimen scores for samples of the two species projected on first and second canonical variates segregate into two discrete clusters along the first axis, a large one formed by combined population samples of B. chrysocomus , and a smaller group representing specimens of B. coelestis (fig. 42, lower graph). The dispersal is influenced by moderate to high negative correlations (r 5 ‾ 0.25 to ‾ 0.76; table 32) reflecting the generally larger skull and greater internal dimensions of B. coelestis (revealed also in univariate means; table 31) as compared with B. chrysocomus ; covariation in lengths of diastema and incisive foramina, along with height of braincase, exerts the most force (table 32). In contrast, B. coelestis has a narrower incisive foramina and mesopterygoid fossa compared to B. chrysocomus .

The high positive loading on the second axis for breadth of zygomatic plate (r 5 0.74) and lesser negative values for lengths of bulla and molar row, and molar breadth (r 5 ‾ 0.43, ‾ 0.27, and ‾ 0.14, respectively) reflect the relatively wider plate of B. coelestis and its relatively smaller bullae and weaker molars compared to most specimens in the sample of B. chrysocomus .

In summary, B. coelestis has an overall larger cranium than B. chrysocomus , in which the rostrum is especially longer and thinner, the incisive foramina longer and narrower, the zygomatic plate wider, and the braincase higher. The mesopterygoid fossa and first upper molar are narrower, and bulla and molar row shorter relative to overall cranial size as compared with B. chrysocomus .

Results of UPGMA cluster analysis derived from Mahalanobis distances among centroids as a phenetic measure of resemblance also highlights the separation of B. coelestis from all population samples of B. chrysocomus (fig. 49).

Cranial contrasts between the two species are mirrored by mandibular distinctions (fig. 39). Compared with B. chrysocomus , the region between anterior margin of first molar and the incisor alveolus (diastema) is longer in B. coelestis and body of the ramus is not as high, resulting in a lower and more elongate structure. Bunomys coelestis also has appreciably longer and more slender lower incisors.

Occlusal patterns of molars are similar in B. chrysocomus and B. coelestis except for frequency of small cusps and cusplets found on certain molars. Nearly all specimens (25 of 28) in the sample of B. coelestis have a small cusp t3 on the second upper molar, but t3 is lost in most examples (164 of 197) of B. chrysocomus (table 10). Anterior labial cusplets could not be identified on first lower molars of any of the 24 specimens of B. coelestis surveyed, and occurred on the third lower molars only in 8 of the 24 examples. By contrast, first lower molars in about half of the sampled B. chrysocomus (62 of 120 specimens) exhibit anterior labial cusplets, and third lower molars in appreciably more than half of the sample (78 of 120) have such cusplets (table 11).

The morphological external, cranial, and dental configuration of B. coelestis is basically a slight but distinguishable modification of the anatomy seen in B. chrysocomus . Samples of the latter collected in montane forest habitats come from Gunung Kanino (1189–1555), Gunung Lehio (1880–2185 m), and Pegunungan Latimojong (2200 m) in the west-central mountain block; Gunung Tambusisi (1372–1830 m) at the western margin of the eastern peninsula; and Pegunungan Mekongga (2000 m) on the southeastern peninsula. Except for their long fur, none of these specimens exhibit the traits diagnostic of B. coelestis , and closely resemble the external, cranial, and dental features in samples of B. chrysocomus collected from lower elevations in the west-central region and southeastern peninsula (see account of B. chrysocomus ).

GEOGRAPHIC VARIATION: There is no evidence that B. coelestis occurs anywhere else than above 1800 m on the forested slopes of Gunung Lompobatang, the high volcano that looms over the tip of the southwest peninsula (fig. 1). The specimens listed here constitute a single population sample of the species, and is large enough to be composed of age categories ranging from young to old adults. What intrasample variation I detected is expressed as differences in external, cranial and dental measurements reflecting age composition as well as individual differences among specimens of comparable ages. The extent of morphometric variation, for example, is indicated in summary statistics (table 31) and the generally tight cluster of specimen scores in the ordinations derived from principal-components and discriminant-function analyses (fig. 42).

NATURAL HISTORY: I lack firsthand experience with B. coelestis in its natural habitat, and field journals of collectors are devoid of useful ecological information. Long, thick, and dark fur, long claws on the forefeet, elongate rostrum and mandible, and protracted lower incisors, which are characteristic of B. coelestis , are traits associated with murine species living in cool and wet habitats of montane evergreen rain forests, at least in Sulawesi. Because in its morphology, B. coelestis appears to be a montane relative of B. chrysocomus , I suspect it to be terrestrial and have a similar diet—primarily earthworms, snails, arthropods, small vertebrates, along with some fruit. Its reproductive traits are also probably similar to those of B. chrysocomus . Results of extended fieldwork in patches of montane forest remaining on the volcano would test these suppositions.

ECTOPARASITES: Bunomys coelestis is parasitized by the tiny fur mite Listrophoroides (Marquesania) cucullatus (table 14), which is also found on Sulawesian Rattus hoffmanni and R. xanthurus as well as a variety of murines from the Indoaustralian region and Philippines ( Bochkov and Fain, 2003: 577).

SYNONYMS: None.

A species so far known only from montane habitats on Gunung Tambusisi at the western end of the eastern peninsula is the subject of the following account.