Bunomys prolatus Musser, 1991

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 : 116-124

Bunomys prolatus Musser, 1991

Bunomys prolatus Musser, 1991: 4 .

HOLOTYPE: MZB 12190, the skin and skull of an adult male (original number 25) collected March 9, 1980, by C.H.S. Watts. External, cranial, and dental measurements, along with other data, are listed in table 18. Pieces are missing from both skin and skull; I have already described the extent of this damage (Musser, 1991: 4).

TYPE LOCALITY: Gunung Tambusisi (‘‘Tambusisi Ridge’’) (01 ° 38 9 S, 121 ° 23 9 E), 6000 ft (1830 m; locality 1 in gazetteer and the map in fig. 22), near the western end of the eastern peninsula of the island, Propinsi Sulawesi Tengah, Indonesia (see fig. 1) .

EMENDED DIAGNOSIS: One of the largest in physical size among members of the Bunomys chrysocomus group ( LHB 5 156– 179 mm, ONL 5 40.4–43.2 mm) and further distinguished from members in that assemblage by the following combination of traits: (1) long, dense, and very soft fur; (2) tail that is much shorter than combined lengths of head and body (LT/ LHB 5 79 %), dorsal surface brown, ventral surface grayish brown, white, or white speckled with brown; (3) white tail tip typically absent (a 2 mm white tip present on one of seven specimens); (4) short hind foot relative to body size; (5) large, darkly pigmented epidermal scales on dorsal surfaces of fore- and hind feet as well as digits; (6) large and strong elongate claws with curved and sharp tips; (7) elongate cranium and mandible, long and tapered rostrum (with an associated long diastema and incisive foramina), wide interorbital region, and large braincase and auditory bulla; (8) narrow across zygomatic arches and narrow zygomatic plates; (9) long molar rows and wide molars; (10) cusp t3 absent from second and third upper molars; and (11) no anterolabial cusp on first lower molar and most specimens with anterolabial cusp on third molar.

GEOGRAPHIC AND ELEVATIONAL DISTRI- BUTIONS: The sample of B. prolatus was collected at 1830 m, an elevation that Whitten et al. (1987: 521) surmise is in the zone of upper montane forest on Gunung Tambusisi (‘‘between 1700 and 2500 m’’). Trapping efforts by members of the expedition did not extend higher. Presumably the species occurs in suitable habitat elsewhere on the mountain, possibly up to the summit (which is at 2422 m according to Whitten et al., 1987: 521). I suspect B. prolatus to be confined to montane evergreen rainforest formations—its actual altitudinal limits can be determined only by future survey.

Maryanto and Yani (2003) and Maryanto et al. (2009) have recorded B. prolatus from Lore Lindu National Park in central Sulawesi, which is certainly based on a misidentification (DNA has recently been extracted from a voucher specimen in Maryanto’s Lore Lindu collection that was labeled ‘‘ Bunomys prolatus , ’’ but the DNA sequence identifies it as B. chrysocomus ; Ken Aplin, personal commun., 2011). My transect was in what is now Lore Lindu National Park, and I never encountered the species, even during the months camped in montane forests on Gunung Kanino and Gunung Nokilalaki. Highland regions surveyed by other collectors outside but adjacent to the Park boundaries, and those sampled farther south in the west-central mountain block have never yielded B. prolatus ; the species is recorded only from Gunung Tambusisi, which is at the western part of the eastern

TABLE 31

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from All Population Samples for Bunomys chrysocomus , B. coelestis , B. prolatus , and B. torajae n. sp.

Mean ± 1 SD and observed range (in parentheses) are listed.

peninsula (fig. 1). Outside of Gunung Tambusisi, the places to expect B. prolatus are in the other highland regions of the eastern arm: Pegunungan Tokala to the east of Gunung Tambusisi; Gunung Katopasa to the north; and Pegunungan Balinggara (containing Gunung Bulutumpu) farther out on the peninsula (see the map in Whitten et al., 1987: 498). These mountains and stretches of highlands connecting them are high enough to support montane forest, and all, including Gunung Tambusis, are isolated from the expansive west-central mountain block in the central core of the island. Except on Gunung Lompobatang in the southwestern peninsula, and on the northern peninsula, B. penitus is the common Bunomys occurring in all montane forests surveyed outside of the eastern peninsular highlands. Bunomys prolatus may represent its ecological replacement

TABLE 32 Results of Principal-Components and Discriminant-function analyses Comparing All Population Samples of Bunomys chrysocomus with the Sample of B. coelestis Correlations (loadings) of 16 cranial and two dental log-transformed variables are based on 232 B. chrysocomus and 18 B. coelestis ; see figure 42.

on Gunung Tambusisi, as well as the other nearby mountain expanses; those highlands have yet to be surveyed for their small mammal faunas.

SYMPATRY WITH OTHER BUNOMYS : Bunomys prolatus and B. chrysocomus have been collected on the slopes of Gunung Tambusisi (see Musser, 1991, and tables 6, 20). The eight known specimens of B. prolatus were trapped on a ridge at 1830 m in upper montane forest. One B. chrysocomus was taken ‘‘just below the same ridge, at about the same altitude (6000 ft [1830 m]) but a few meters downslope, and on the same day (March 9) as were four examples of B. prolatus . Six specimens of B. chrysocomus were collected at 4500 [1372 m] and 4700 ft [1433 m] during the same period, March 6– 27, 1980 ’’ (Musser, 1991: 6). C.H.S. Watts, the collector, wrote me (Musser, 1991: 40) that he ‘‘recalls catching the B. prolatus in traps set in short and very mossy forest along a ridgetop and the example of B. chrysocomus about 10 m below the ridge itself. He clearly remembers being impressed by the sharp and sudden vegetative transition between the ridgetop and just below it, and the concordant change in species of Bunomys . ’’ Watts’ samples of both species are small and whether the altitudinal ranges of each narrowly overlap or the two are truely altitudinally parapatric can only be determined by careful trapping efforts during future surveys.

DESCRIPTION: Bunomys prolatus is the largest in physical size among species in the B. chrysocomus group (LHB 5 156–179 mm, LT 5 125–142 mm, LHF 5 33–35 mm. LE 5 24–26 mm, ONL 5 40.4–43.2 mm), has a protracted face between eyes and nose, short tail and hind feet relative to combined lengths of head and body (LT/LHB 5 79 %, LHF/ LHB 5 20 %), and brownish-gray fur that is long, soft, and dense. The elongate skull and mandible are portrayed in figures 37–39, and occlusal patterns of the molars in figure 40. I have elsewhere provided a full description of the skin, skull, and dentition of the species (Musser, 1991).

The Latin prolatus means ‘‘elongate’’ and is an appropriate name for this species of Bunomys characterized by its elongate face, skull, and front claws.

KARYOTYPE: No information.

COMPARISONS: Among species of Bunomys , B. prolatus is morphologically (and phenetically) most similar to B. chrysocomus , B. coelestis , and B. torajae , n. sp. Here I compare B. prolatus with the first two species; contrasts between B. prolatus and B. torajae , n. sp., will be presented in the following account where that new species is described. Bunomys prolatus will be compared with certain population samples of B. andrewsi and B. penitus —members of the B. fratrorum group—in each of those respective accounts.

Bunomys prolatus and B. chrysocomus: Elsewhere I detailed contrasts and similarities between the two species (Musser, 1991), and here will only summarize major differences. Compared with samples of B. chrysocomus from throughout its documented geographic range (see the map in fig. 22), the sample of B. prolatus averages larger in body size (indicated by combined length of head and body), has shorter hind feet and tail (absolutely and relative to length of head and body; table 19), longer pelage, strikingly more robust and longer claws on the forefeet (fig. 36), and more extensive brown epidermal scutellation on dorsal surfaces of feet and digits.

Differences in absolute size and proportions summarize the primary morphometric cranial and dental contrasts between the two species: B. prolatus has a larger skull and molars and differs in proportions of internal cranial dimensions. The contrast is evident in the cranial illustrations of B. prolatus and B. chrysocomus (figs. 37–39), univariate descriptive statistics (table 31), and the ordination of specimen scores for samples of B. prolatus and B. chrysocomus projected on first and second principal components (fig. 43). Size is the primary factor dispersing the spread of scores along the first axis with scores for B. prolatus and the larger specimens of B. chrysocomus falling in the right half of the scatter plot; positive and moderate to high loadings for nearly all variables are respon- sible for this distribution (r 5 0.19–0.81; table 33). Univariate means of most measurements are greater in the sample of B. prolatus than in samples of B. chrysocomus (table 31). The isolation of the B. prolatus cluster along the second axis (shape factor) underscores its relatively wider interorbit; larger braincase; and longer rostrum, diastema, bony palate, incisive foramina, bullar capsule, and molar row compared with B. chrysocomus (table 33). Also predominant in isolating the scores for B. prolatus at the top of the scatter plot is its relatively narrower skull (breadth across the zygomatic arches) and rostrum compared with the conformation in B. chrysocomus , its relatively much narrower zygomatic plate, and relatively slightly narrower bony palate, mesopterygoid fossa, and incisive foramina; univariate mean values for these measurements are similar in the two species, indicating that the dimensions are relatively smaller in B. prolatus compared with B. chrysocomus . This quantification reinforces the visual contrast between the two species when skulls are compared side by side: B. prolatus has larger molars than B. chrysocomus , a cranium that is about as wide (except for interorbit and braincase) but significantly longer—protract- ed by comparison with the skull of B. chrysocomus —with a relatively narrower zygomatic plate, rostrum, and bony palate (figs. 37–39).

The primary mandibular difference between the two species mirrors the cranial contrasts. Bunomys prolatus has longer dentaries, particularly in the more elongate bony stretch between incisor alveolus and anterior margin of the molar row (fig. 39).

Frequency of some cusps and cusplets differ. A cusp t3 is not present on any example of Bunomys prolatus , but is part of the occlusal surface on the second molar in 17 % of the B. chrysocomus sample, and on the third molar in 5 % of the sample (table 10). All specimens of B. prolatus lack an anterior labial cuspet on the first lower molar; such a cusp occurs in 52 % of the sample of B. chrysocomus (table 11).

Bunomys prolatus and B. coelestis: These two species have been collected only from montane forest habitats. Both have dark, soft, and long fur, long front claws (fig. 36), a large cranium with an elongate rostrum, and long and gracile mandible (figs. 37–39). Bunomys prolatus is larger than B. coelestis , as indexed by its average longer head and body, hind foot, and ears, but has a shorter tail (absolutely relative to length of head and body; LT/LHB 5 79 % for B. prolatus , 95 % for B. coelestis ). The Tambusisi rat has larger, longer, and more robust claws on digits of the front feet (fig. 36) as well as more extensive brown epidermal scutellation on dorsal surfaces of the feet and digits.

Bunomys prolatus has a larger skull than B. coelestis , as indicated by the greater size of most of its cranial and dental dimensions; however, a few other cranial variables are of lesser magnitude than comparable dimensions in B. coelestis (table 31). These two sets of contrasts are quantitatively summarized through principal-components analysis. Specimen scores for B. coelestis and B. prolatus

TABLE 33 Results of Principal-Components Analysis Contrasting Samples of Bunomys prolatus with Those of B. chrysocomus , and B. coelestis Correlations (loadings) of 16 cranial and two dental log-transformed variables are based on 232 B. chrysocomus , 18 B. coelestis , and 8 B. prolatus ; see figure 43.

projected onto first and second principal components form two widely separated clusters along the first axis (fig. 43). Their positions are determined primarily by the large and positive loadings for skull length; breadths of interorbit and braincase; lengths of rostrum, bony palate, bullar capsule; and size of molars (r 5 0.57–0.77; table 33). Compared with B. coelestis , the Tambusisi species has a longer skull, wider interorbital region and braincase, longer rostrum and bony palate, larger bullar capsule, and heavier molars. The negative loadings associated with the first principal component points to the less-flared zygomatic arches (narrower zygomatic breadth) of B. prolatus compared with B. coelestis , along with its shallower braincase, much narrower zygomatic plate, and shorter diastema (the counterpoint to the longer bony palate and molar rows in B. prolatus ). These dimensional contrasts between the two species are reflected in univariate means for the variables (table 31) and can be visually appreciated in the illustrations of skulls (figs. 37–39).

Frequency of particular cusps and cusplets differ. Cusp t3 is absent from second and third upper molars of all examples of B. prolatus , but in B. coelestis is present on the second upper in 89 % of the sample and on the third molar in 5 % (table 10). An anterolabial cusp is present on the third lower molar in 75 % of the B. prolatus sample but only in 25 % of the sample of B. coelestis (table 11).

GEOGRAPHIC VARIATION: Because all the specimens of B. prolatus were taken in one trapline at a single locality, I cannot assess variation associated with geography. The differences in coat color among the specimens I have already described (Musser, 1991) and the range in measurements for each variable reflect individual variation and variation attributable to age among the adult specimens. Age-related size differences among crania, ranging from old adult (the largest) to adult and finally young adult (the smallest) individuals, is illustrated elsewhere (Musser, 1991: 20).

NATURAL HISTORY: All information concerning B. prolatus comes from the collector, C.H.S. Watts (in litt., 1980). The specimens were trapped on a ridgetop at 1830 m in forest where the trees were short (4 m) and gnarled, and on exposed areas the vegetation was heathlike. Pitcher plants (Nepheris) abounded and the ground was deeply covered in moss. On Gunung Tambusisi, 1830 m is in the zone of upper montane forest ( Whitten et al., 1987: 521). One individual was caught in deep moss during the day between 10 and 11 A.M.; all the others were taken during the night.

A female had one recent placental scar.

The external morphology of B. prolatus is that of a terrestrial rat. Its long muzzle, very long and strong claws, and overall skull conformation suggests a diet consisting primarily of invertebrates, likely containing a range of items similar to those eaten by B. chrysocomus (see that account and table 13).

ECTOPARASITES: Bunomys prolatus is host to the flea Sigmactenus alticola pilosus (table 14), and that ectoparasite has also been recorded from 14 other species of endemic Sulawesi murine rodents ( Bunomys penitus , B. chrysocomus , and B. karokophilus , n. sp.; Margaretamys elegans ; Maxomys hellwaldii , M. wattsi , and Maxomys sp. ; Melasmothrix naso and Tateomys rhinogradoides ; Paruromys dominator ; Taeromys celebensis and Taeromys sp. ; Rattus hoffmanni and R. facetus [recorded as R. marmosurus ]) and the nonnative Rattus exulans ( Durden and Beaucournu, 2000) .

The nematode, Syphacia rifaii (Oxyuroidea, Oxyuridae ), was extracted from host specimens identified as B. prolatus that were collected in Lore Lindu ( Dewi and Hasegawa, 2010), but the host rats are likely examples of B. chrysocomus and not B. prolatus .

SYNONYMS: None.

The next account also deals with another montane isolate, one phenetically closely allied with Bunomys prolatus but occurring far to the south of Gunung Tambusisi in the high mountainous landscape of the Quarles Range in the southern part of the westcentral mountain block. The species is named and described here by the four authors listed and they should be cited as the authorities for the name.

Bunomys torajae , new species, G.G. Musser,