Soricomys musseri ( Rickart et al., 1998 )

Balete, Danilo S., Rickart, Eric A., Heaney, Lawrence R., Alviola, Phillip A., Duya, Melizar V., Duya, Mariano Roy M., Sosa, Timothy & Jansa, Sharon A., 2012, Archboldomys (Muridae: Murinae) Reconsidered: A New Genus and Three New Species of Shrew Mice from Luzon Island, Philippines, American Museum Novitates 2012 (3754), pp. 1-60 : 40-41

Soricomys musseri ( Rickart et al., 1998)

Archboldomys musseri Rickart, Heaney, Tabaranza, and Balete, 1998: 17 .

HOLOTYPE: FMNH 147176 . Adult male collected on 15 May 1992, field number D.S. Balete 2092 (figs. 10–11; Rickart et al., 1998: figs. 8–10). Initially fixed in formalin, now preserved in ethyl alcohol with skull removed and cleaned. Fresh tissues were removed from the thigh at the time of capture and placed in ethanol. The holotype is currently housed at the FMNH, but will be transferred to the PNM.

TYPE LOCALITY: Philippines: Luzon Island: Cagayan Province: Peñablanca Municipality: Barangay Callao : Mt. Cetaceo , 1650 m elevation, 17°42´N, 122°02´E (fig. 1). See comments below .

MEASUREMENTS: Tables 3 and 4.

SPECIMENS EXAMINED (N = 5): Cagayan Province, Peñablanca Municipality, Mt. Cetaceo , 1650 m ( FMNH 147176 [holotype]) ; 1.5 km SW Mt. Cetaceo peak, 1550 m ( FMNH 185907 , 185910 ) ; 2.0 km SW Mt. Cetaceo peak, 1500 m ( FMNH 185908 , 185909 ) .

EMENDED DIAGNOSIS: A species of Soricomys distinguished from congeners by the following combination of characters: (1) dark, reddish-brown fur dorsally, shorter and paler ventrally; (2) absolutely and relatively shorter hind foot; (3) longer nasals; (4) dorsally inflated and higher cranium; (5) shorter and broader tympanic hook; (6) narrower squamoso-mastoid vacuity; (7) spacious postglenoid vacuity; (8) slender, backswept coronoid process; and (9) narrow, broadly angled angular process relative to condyle, and nearly straight-edged dorsally (figs. 9–11).

COMPARISONS: Externally most similar to S. leonardocoi , n. sp., but distinguished by the following combination of features (figs. 9–11, 13, 14, tables 3, 4, 11; Rickart et al., 1998: figs. 6–8, 12, 13): (1) absolutely and relatively shorter hind foot; (2) shorter, paler fur; (3) relatively longer tail; (4) narrower interorbit; (5) greater zygomatic breadth; (6) narrower zygomatic plate; (7) longer nasals; (8) shorter incisive foramina; (9) narrower squamoso-mastoid vacuity; (10) shorter maxillary molar tooth row; (11) narrower first upper molars, M1; and (12) broader incisors at their tips. Distinguished from S. kalinga by the following combination of features (figs. 9–11, tables 3, 4; Balete et al., 2006: figs. 4–6; Rickart et al., 1998: figs. 6–8, 12, 13): (1) relatively shorter tail; (2) absolutely and relatively shorter hind foot; (3) longer, darker fur; (4) dorsolaterally inflated cranium; (5) higher braincase; (6) broader interorbit; (7) wider zygomatic breadth; (8) longer nasals; (9) narrower squamoso-mastoid vacuity; (10) longer maxillary molar row; (11) wider palatal breadth at M1; and (12) wider labial breadth at M3. Distinguished from S. montanus , n. sp., by the following combination of features: (1) relatively shorter tail; (2) relatively shorter hind foot; (3) higher and dorsolaterally inflated cranium; (4) greater zygomatic breadth; (5) shorter and shallower rostrum; (6) longer nasals; (7) greater orbitotemporal length; (8) longer maxillary molar row (M1–M3); (9) wider palatal breadth at M1; (10) shorter diastema; (11) greater postpalatal length; (12) greater labial palatal breadth at M3; (13) wider incisors at their tips; (14) narrower zygomatic plate.

A PCA analysis of cranial and dental measurements (fig. 4, table 5) that included all species of Archboldomys and Soricomys (fig. 4, table 5) demonstrated clear separation of S. musseri from Soricomys leonardocoi , n. sp., on the second axis, with S. kalinga , S. montanus , n. sp., and S. musseri having a proportionately longer skull, more elongate diastema and postpalatal region, and broader upper incisors near their tips, and S. leonardocoi , n. sp., having the converse. Soricomys musseri differed from S. kalinga slightly on the first axis, an indication of its overall larger size. Soricomys musseri was most similar to S. montanus , n. sp., differing in scoring slightly higher on the first axis, indicating greater size. A PCA that included only the four species of Soricomys (fig. 5, table 6) produced similar results, with S. musseri loading less heavily on the first component and more heavily on the second component than S. leonardocoi , n. sp., indicating that S. musseri averages smaller overall and has shorter basioccipital length, rostral depth, rostral length, diastema length, and breadth of incisors near their tips. Soricomys musseri differed from S. kalinga and S. montanus , n. sp., in this PCA on the first component, which generally indicates its larger size.

DISTRIBUTION: Currently known only from Mt. Cetaceo, in the northern Sierra Madre from 1500 m to 1650 m (figs. 1, 15; Duya et al., 2011). We hypothesize that it will be found north from Mt. Cetaceo (1730 m) to the Twin Peaks (peak at 1603 m) to at least as far south as Mt. Cresta (1672 m) in Isabela Province, and possibly from Mt. Palanan (1212 m) in southern Isabela Province to Mt. Anacuao (1853 m) in Aurora Province; these areas are typically (though intermittently) above 1500 m (fig. 15).

ECOLOGY: Soricomys musseri has been documented in montane and mossy forest on Mt. Cetaceo, from 1500 m to 1650 m ( Rickart et al., 1998; Duya et al., 2007, 2011). Based on trapping success, S. musseri appeared to be uncommon, with only four captures in 2395 ground-trap nights; the majority (75%, N = 3) were caught with earthworm bait, possibly indicating a vermivorous diet ( Duya et al., 2011). Males with scrotal testes were captured in May and June; the two females, captured in June, were young adults with two pairs of small inguinal mammae. Also recorded in the montane and mossy forest habitat of S. musseri were two other members of the Chrotomys Division: Apomys musculus and A. sierrae ; another member of the clade, A. microdon , was documented slightly lower on the mountain, at 1400 m (table 12). Other nonvolant small mammals recorded on the mountain included Crocidura grayi , Bullimus luzonicus , and Rattus everetti ( Duya et al., 2011) .

COMMENTS: The attribution of the type locality in the original description to Callao Municipality was erroneous, as Callao is actually a barangay (a smaller political unit within a municipality), instead of Peñablanca, which is the correct name of the municipality. The first specimen, which later became the holotype of this species, was initially reported as Crunomys fallax (Danielsen et al., 1994) .