Soricomys kalinga (Balete, Rickart, and Heaney, 2006 )

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 : 41-52

Soricomys kalinga (Balete, Rickart, and Heaney, 2006)

Archboldomys kalinga Balete, Rickart, and Heaney, 2006: 491 .

HOLOTYPE: FMNH 175555 . Adult male collected on 23 February 2003, field number E.A. Rickart 5001 (figs. 9–11). Fresh tissues were removed from the thigh and placed in 95% ethanol. The rest of the specimen was initially fixed in formalin, now preserved in 70% ethyl alcohol with skull removed and cleaned. The holotype is currently housed at FMNH, but will be transferred to PNM.

TYPE LOCALITY: Philippines: Luzon Island: Kalinga Province: Balbalan Municipality: Mt. Bali-it , 1950 m elevation, 17°25.8´N, 121°00.1´E (fig. 1) .

MEASUREMENTS: Tables 3 and 4.

SPECIMENS EXAMINED (N = 22): Kalinga Province: Balbalan Municipality, Am-licao , 1800 m ( FMNH 169122–169124 , 170965–170967 ) , Magdallao , 1600 m ( FMNH 167304–167309 ) , Mt. Bali-it, 1950 m ( FMNH 175552–175555 [holotype], 175556), Mt. Bali-it , 2150 m ( FMNH 175557–175559 , 175720 , 175721 ) .

EMENDED DIAGNOSIS: A small shrew mouse of the genus Soricomys , distinguished from congeners by the following combination of features: (1) uniformly orange-brown dorsal pelage, shorter and paler on the venter; (2) narrow, dorsally flattened cranium; (3) long and slender tympanic hook; (4) deep rostrum; (5) long diastema; (6) narrow palate at M1; (7) short maxillary molar row; (8) short first upper molars; (9) robust, broadly backswept coronoid process; (10) robust, broadly tapered condyle; and (11) short, robust angular process (figs. 9–11).

KARYOLOGY: 2N = 44; FN unknown (fig. 6B; Rickart and Heaney, 2002).

COMPARISONS: Distinguished from S. musseri , n. sp., by the following features (tables 3, 4; figs. 9–11; Rickart et al., 1998: figs. 10, 12, 13; Balete et al., 2006: figs. 2–6): (1) larger body size overall; (2) relatively longer tail; (3) absolutely and relatively longer hind foot; (4) shorter and paler pelage; (5) flatter and lower cranium; (6) narrower interorbit; (7) narrower zygomatic breadth; (8) shorter nasals; (9) wider squamoso-mastoid vacuity; (10) shorter molar row; (11) narrower palate at M1; (12) narrower lingual palatal breadth at M3; (13) robust and broadly backswept coronoid process; (14) broader condyle; and (15) shorter, decurved angular process.

Distinguished from S. montanus , n. sp. (figs. 9, 14, 16; tables 3, 4), by the combination of the following features: (1) longer body size overall; (2) paler pelage; (3) relatively longer tail; (4) shorter skull with flatter cranium; (5) narrower interorbital region; (6) greater zygomatic breadth; (7) narrower mastoidal breadth; (8) shorter and shallower rostrum; (9) greater orbitotemporal length; (10) longer diastema; (11) longer postpalatal region; (12) wider incisors at their tips; (13) wider zygomatic plate.

Distinguished from S. leonardocoi , n. sp., by the following combination of features (figs. 9, 14, 17, tables 3, 4; Balete et al., 2006: figs. 2–6): (1) small body overall; (2) relatively longer tail; (3) relatively longer hind foot; (4) shorter, narrower skull; (5) lower and flatter braincase; (6) narrower interorbital region; (7) wider squamoso-mastoid vacuity; (8) longer diastema; (9) shorter postpalatal region; (10) shorter maxillary molar row; (11) smaller M1; (12) narrower palate at M1; (13) narrower labial breadth at M3; (14) broader incisors at their tips; (15) broader, more robust condyle; and (16) robust, backswept coronoid process.

A PCA analysis of cranial and dental measurements that included all species of Archboldomys and Soricomys (fig. 4, table 5) showed good separation from S. leonardocoi , n. sp., on the second axis, with S. kalinga , S. montanus , n. sp., and S. musseri having a proportionally longer skull, more elongate diastema and postpalatal region, and broader upper incisors near the tip, and S. leonardocoi , n. sp., having the converse. Soricomys musseri differed from S. kalinga and S. montanus slightly on the first axis, an indication of its overall larger size. A second PCA that included only the four species of Soricomys (fig. 5, table 6) showed separation of S. kalinga from S. musseri and S. leonardocoi , n. sp., on the first component, primarily reflecting the overall larger size of those species. Soricomys kalinga overlapped with S. montanus extensively on the first two components, but had less overlap on the third and fourth components, indicating that S. kalinga tends to have greater zygomatic breadth, shorter incisive foramina, greater orbito-temporal fossa length, greater lingual breadth of palate at M3, and broader incisors near their tips, and greater postpostatal length and broader zygomatic plates.

DISTRIBUTION: Soricomys kalinga is currently known from the northern portion of the Central Cordillera of northern Luzon, where it has been documented at localities on Mt. Bali-it in Balbalan Municipality, Kalinga Province (figs. 1, 15). Inspection of figure 15 leads us to suggest that this species occurs north of the drainages of the Agno and Chico rivers (including the Sabangan river, a tributary of the Chico); these two drainages form a declivity across the crest of the Central Cordillera, with their headwaters meeting at a narrow pass that reaches a maximum elevation of about 1800 m, a short distance to the northwest of Mt. Data. On this basis, we hypothesize that this species will be found to occur from approximately Mt. Tinangdanan (ca. 5 km SW of Sagada) along the chain of mountains stretching NNE to at least as far as Mt. Macopa, which lies along the boundary of Abra and Apayao provinces. The type locality lies slightly north of the center of this hypothesized distribution (fig. 15).

ECOLOGY: Soricomys kalinga occured in mature montane and mossy forest from ca. 1600 m to 2150 m on Mt. Bali-it in Balbalan Municipality, Kalinga Province, where it was predominantly diurnal and had significant preference for earthworm bait (Balete et al., 2006; Rickart et al., 2011a). The stomach contents included finely chewed arthropod exoskeletons, larval arthropods, and earthworms, suggesting an insectivore/vermivore feeding habit. Other species documented sympatrically with S. kalinga were: Crocidura grayi , Apomys abrae , A. datae , A. microdon , A. musculus , Batomys granti , Bullimus luzonicus , Carpomys phaeurus , Chrotomys silaceus , Chrotomys whiteheadi , Rattus everetti , and Rhynchomys soricoides ; Phloeomys pallidus also occurred in the vicinity (Balete et al., 2006; Rickart et al., 2011a).

Females have two pairs of inguinal mammae. Males with scrotal testes were captured in February, and pregnancy was recorded in April: two pregnant females each bore two embryos, and one also had one placental scar (Balete et al., 2006).

COMMENTS: The karyotype (fig. 6B; initially reported as A. musseri ; Rickart and Heaney, 2002) is based on a poor quality in vitro preparation. It is similar to S. montanus , n. sp. (2N = 44) and differs from A. luzonensis (2N = 26) as described above.

Soricomys montanus , new species

Figures 9 , 12B, 14, 16

Archboldomys kalinga, Heaney et al., 2010 (part, included series from Mt. Amuyao, Mt. Data, and Mt. Pulag).

Archboldomys kalinga, Rickart et al., 2011a: 532 (part, included series from Mt. Amuyao, Mt. Data, and Mt. Pulag).

HOLOTYPE: FMNH 188314 . Adult male collected on 3 March 2006; field number D.S. Balete 3788. Fresh tissues were removed from the thigh and placed in DMSO buffer. The rest of the specimen was initially fixed in formalin, now preserved in ethyl alcohol with skull removed and cleaned. It is currently housed at FMNH, but will be transferred to PNM.

TYPE LOCALITY: Philippines: Luzon Island: Mountain Province: 0.75 km N, 0.6 km E south peak of Mt. Data , 2241 m elevation, 16.86287° N, 120.86108° E (fig. 1) .

MEASUREMENTS: Tables 3 and 4.

SPECIMENS EXAMINED (N = 18): Benguet Province, Bokod Municipality, Mt. Pulag National Park , 0.5 km S, 0.4 km W Mt. Babadak peak, 2480 m ( FMNH 198175 ) ; Mountain Province: Barlig Municipality, Mt. Amuyao peak, 2690 m ( FMNH 193516 ) , 0.5 km N, 0.5 km W Mt. Amuyao peak, 2530 m ( FMNH 193514 , 193515 ) , 0.75 km W Mt. Amuyao peak, 2300 m ( FMNH 193517 ) , 1.0 km N, 1.0 km W Mt. Amuyao peak, 2150 m ( FMNH 193518–193520 ) ; Bauko Municipality, Mt. Data , 0.75 km E south peak, 2310 m ( FMNH 188318 ) , 0.75 km N, 0.6 km E south peak, 2241 m ( FMNH 188314–188317 ) , 0.75 km N, 0.75 km E south peak, 2289 m ( FMNH 188319 ) , 0.75 km N, 1.0 km E south peak, 2289 m ( FMNH 188320 , 188449 ) .

ETYMOLOGY: From the Latin montanus , meaning “pertaining to mountains,” in recognition of its distribution in the high mountains of the Central Cordillera, including Mountain Province. We suggest “southern Cordillera shrew mouse” as an English common name. DIAGNOSIS: A slender-bodied member of Soricomys , distinguished from congeners by the following combination of features: (1) smaller body size overall; (2) shorter length of combined head and body; (3) pelage dark reddish brown dorsally, shorter and paler orange-brown ventrally; (4) greater rostral depth; (5) greater orbitotemporal length; (6) shorter postpalatal region. DESCRIPTION AND COMPARISONS: Soricomys montanus is a small-bodied murid (20–31 g), with a tail equal to or slightly shorter than the combined length of head and body (table 3). The pelage of S. montanus is dark reddish brown dorsally, slightly shorter and paler ventrally (fig. 12B). The dorsal hair is tricolored, medium gray on the basal three-fourths, followed by a dark gray band with a reddishbrown distal quarter. The lips and rhinarium are pale grayish brown. The eyelids are edged in black, surrounded by a pale reddish-brown ring of short fur. The dark gray to black mys- FIG. 16. Cranium and mandible of Soricomys montanus, adult male (FMNH 188314, holotype) in tacial vibrissae are moderately long, extending dorsal, ventral, and lateral views. beyond the ears. The ears are rounded, uniformly dark gray, and covered with short, dark gray hairs. The hind feet are slender and with long digits bearing long, opaque claws. Their dorsal surface is uniformly grayish brown, darker on the plantar surface and plantar pads. The front feet of S. montanus are small and have slender digits bearing long, opaque claws with decurved tips, except the pollex, which is reduced to a stump and bears a nail. The dorsal surface of the forefeet and the palmar surface, including the palmar pads, is uniformly pale grayish brown. Soricomys montanus is similar to congeners in overall body form, but closest to S. kalinga in most external features and body proportions (fig. 12B, table 3; Balete et al., 2006: fig. 3). It differs from the latter by the following combination of features: (1) smaller and shorter body overall (larger and longer in S. kalinga ); (2) darker pelage (paler); and (3) shorter tail (longer). It is distinguished from S. musseri by the following combination of features: (1) smaller body overall;

(larger); (2) longer tail (shorter); and (3) relatively longer hind foot (shorter), and from S. leonardocoi , n. sp., by the following traits: (1) shorter body overall (longer); (2) shorter, paler pelage (longer and darker); (3) relatively longer tail (shorter); and (4) relatively longer hind foot (shorter).

Soricomys montanus has a smooth skull, with a short and tapered rostrum (fig. 16). The cranium is longer than wide, appearing triangular in general outline. The lateral dorsal profile is nearly straight from the top of the skull to the tip of the rostrum. The nasals are straight, and extend to the level of the anterior edges of the premaxillae. The upper incisor root is enclosed in a barely raised bony capsule within the premaxilla and terminates close to the suture with the maxilla, fronting the dorsal opening of the narrow lachrymal canal. The zygomatic plate has a straight anterior edge, and is slightly arched dorsally. The zygomatic process of the squamosal is anchored about 1.5 mm above the dorsal edge of the postglenoid foramen. The tympanic hook of the squamosal is narrow and slender, with a caudad slant. The large mastoid fenestra is situated close to the posterior margin of the mastoid, opposite the elongate mastoid foramen that runs along the barely ossified occipital suture, and merging with the squamosomastoid foramen. Various stages of ossification of the occipital suture and separation of the mastoid and squamoso-mastoid foramina are evident among the paratypes.

The incisive foramina of S. montanus are small, round-edged posteriad and smoothly tapered anteriad; nearly half as long as the diastema (fig. 16, table 4). The alisphenoid canal is small and narrow, partly hidden under the pterygoid ridge (as seen from ventral view), but otherwise fully exposed in the holotype, due to the missing alisphenoid strut reminiscent of the Crunomys pattern, though only partially evident in C. suncoides ( Musser, 1982a: fig. 23; Rickart et al., 1998: figs. 4, 7); in all the paratypes, however, the alisphenoid canal is positioned under the posterior edge of the thin pterygoid ridge, behind the short and narrow alisphenoid strut.

Because the pterygoid strut is absent in the holotype, the pterygoid ridge merges posteriad with the pterygoid bridge that extends over the foramen ovale to the anterior edge of the elongate middle lacerate foramen (fig. 16); in all the paratypes, as in the congeners, the pterygoid ridge terminates posteriad at its juncture with the alisphenoid strut (fig. 16; Rickart et al., 1998: fig. 12). The postglenoid vacuity is spacious and appears broadly triangular due to a blunt (and slightly arched) angle formed by the dorsal confluence of the backward-slanted anterior edge of the tympanic hook and forward-slanted posterior edge of the squamosal, with the straight ventral edge of the periotic part of the petromastoid as its base (fig. 16). This shape of the postglenoid vacuity in S. montanus approximates that of S. kalinga , but in the latter the shorter tympanic hook results in a pronounced anteriad skew (Balete et al., 2006: figs. 4–5); in contrast, it is smoothly arched in S. musseri ( Rickart et al., 1998: figs. 6, 13; Balete et al., 2006: figs. 4–5) and somewhat rectangular in S. leonardocoi , n. sp. (fig. 17). The auditory bulla is relatively small and ventrolaterally inflated, gradually tapering anteriad and smoothly merging with the pointed eustachian tube (fig. 16); in all congeners, this anterior bullar inflation is conspicuous and forms a pronounced constriction that clearly demarcates the boundary with the narrow eustachian tube (figs. 10, 17; Rickart et al., 1998: figs. 12–13; Balete et al., 2006: fig. 4).

The skull of S. montanus closely resembles those of its congeners, but is most similar to S. kalinga . However, it can be distinguished from S. kalinga by the following combination of traits:

(1) longer skull with slightly dorsolaterally inflated cranium (shorter and dorsolaterally flattened in S. kalinga ); (2) zygomatic breadth and zygomatic plate narrower (wider); (3) wider interorbit (narrower); (4) greater mastoidal breadth (narrower); and (5) longer, deeper rostrum (shorter and shallower). Soricomys montanus differs from S. musseri by the following combination of cranial features: (1) dorsolaterally flattened cranium (inflated in S. musseri );

(2) narrower interorbit (broader); (3) zygomatic breadth narrower (broader); (4) broader zygomatic plate (narrower); (5) longer and deeper rostrum (shorter and shallower); (6) shorter nasals (longer); (7) shorter incisive foramina

(longer); and (8) shorter orbito-temporal length

(longer). Soricomys montanus can be distinguished from S. leonardocoi , n. sp., by the following combination of features: (1) shorter skull with dorsolaterally flattened cranium (longer and inflated in S. leonardocoi , n. sp.); (2) narrower interorbital region (wider); (3) greater zygomatic breadth (narrower); (4) narrrower zygomatic plate (wider); (5) longer and deeper rostrum (shorter and shallower); (6) shorter orbito-temporal length (longer); (7) longer diastema (shorter); and (8) shorter postpalatal FIG. 17. Cranium and mandible of Soricomys region (longer). leonardocoi , adult male (FMNH 190972, holotype) The incisors of the new species are small in dorsal, ventral, and lateral views.

and have smooth anterior surfaces, as is typi-

cal of all other species of Soricomys . The upper incisors have orange enamel and emerge from the rostrum at a right angle (orthodont). The lower incisors are long and thinly pointed and have paler enamel. The ventral tips of the upper incisors are nearly straight edged. In ventral view, the outline of the base of each forms a broad “U” shape canted laterally, so that the two incisors form a deep, V-shaped gap along their posteromedial margin (fig. 9). As with congeners, the upper molars are small and narrow. The first upper molar is roughly rectangular in outline, with the convex projection of cusps t1 and t4 forming a distinct bilobed and broadly tapered lingual outline. Cusp t3 is barely discernible in the shallow and sloping labial edge of the coalesced laminar outline of the first row of M1, and difficult to detect in specimens with heavily worn molars; t3 is undetectable in M2 and M3. In both M1 and M2, cusp t9 is barely detectable on the broad laminar outline on their third row, which is largely comprised of the coalesced cusps t7 and t8. M3 is relatively large in relation to M1 and M2, with the broadly convex cusp t1 accounting for nearly half of its occlusal surface, and the rest formed by the coalesced cusps of the second row; the presence of the third row is not evident.

The dentition of S. montanus is similar to congeners, with differences evident mainly in relative sizes of teeth and cuspidation pattern (figs. 9, 14, 16, table 4; Balete et al., 2006: fig. 6; Rickart et al., 1998: fig. 8). The following combination of dental features readily distinguishes it from S. kalinga (figs. 10, 11): (1) slightly longer maxillary molar row (shorter in S. kalinga ); (2) broader first upper molar, M1 (narrower); and (3) narrower incisors at their tips (broader). Soricomys montanus is distinguished from S. musseri by: (1) shorter maxillary molar tooth row (longer in S. musseri ); (2) narrower M1 (broader); and (3) narrower incisors at tip (broader); and from S. leonardocoi , n. sp., by: (1) shorter maxillary molar tooth row (longer in S. leonardocoi , n. sp.); (2) narrower M1 (broader); and (3) wider incisors at their tips (narrower).

Soricomys montanus has mandibles that closely resemble those of its congeners in general shape and placement of mental and mandibular foramina. They differ mainly in relative size and shape of the processes (fig. 16, table 4; Balete et al., 2006: fig. 4; Rickart et al., 1998: fig. 13). The coronoid process is relatively long, robust, and broadly backswept to about two-thirds the length of the condyloid process. In contrast, the coronoid process of S. kalinga is shorter and slender, though equally broadly backswept; it is longer, more delicate, and narrowly backswept in S. musseri ; in S. leonardocoi , n. sp., it is about as long but more slender. The condyloid process of S. montanus is more robust and its angular process relatively shorter than in congeners.

KARYOLOGY: 2N = 44; FN = 52 (fig. 6C).

DISTRIBUTION: Currently known from the southern portion of the Central Cordillera of northern Luzon , in Benguet Province and Mountain Province (fig. 1). As noted above, inspection of figure 15 leads us to suggest that this species occurs south of the drainages of the Agno and Chico rivers (including the Sabangan river , a tributary of the Chico ). On this basis, we hypothesize that this species will be found from south of Mt. Pulag , possibly incuding the vicinity of Mt. Kotkot , near Baguio in Benguet Province, trending north and northeast past Mt. Pulag , Mt. Data , and Mt. Amuyao , ending near the level of Mts. Matingoy and Tangob , at the southern end of Kalinga Province at ca. 17°15´N, east of the Chico River . The type locality lies near the center of this distribution .

ECOLOGY: Soricomys montanus was recorded in old-growth and in lightly disturbed mossy forest from 1800 m to 2690 m on Mt. Amuyao; on Mt. Data it was recorded in heavily disturbed mossy forest at 2241–2310 m, and in similar forest on Mt. Pulag at 2480 m ( Heaney et al., 2006, unpubl. specimens and field notes at FMNH; Rickart et al., 2011b). It showed a high level of tolerance to forest disturbance on Mts. Amuyao, Data, and Pulag, but was absent in heavily disturbed habitats dominated by pine forest or by agriculture at the elevations where they occurred ( Rickart et al., 2011b). We found S. montanus to be predominantly diurnal and to show a preference for earthworm bait (Balete, Heaney, and Rickart field notes at FMNH). On Mt. Amuyao, five of six individuals examined for stomach contents had arthropod remains in their stomachs, and two of them had earthworms. A list of species that cooccurred with S. montanus on Mt. Amuyao is included in the species account for Archboldomys maximus , above.

Females have two pairs of inguinal mammae. On Mt. Amuyao, two of the four females caught in March had large mammae, but neither was pregnant; and four of the five males recorded during the same period had scrotal testes. On Mts. Data and Pulag, only males were documented and all had scrotal testes in March and April, respectively.

COMMENTS: Populations of Soricomys montanus from the three separate mountains (Amuyao, Data, and Pulag) exhibit little apparent variation in external, cranial, and dental features, suggesting their very close affinity (tables 3, 4). This species exhibits the highest intraspecific divergence values in cytochrome b, with populations from Mt. Amuyao differing from those from Mt. Data by 3% (fig. 7).

Soricomys leonardocoi , new species

Figures 9 , 12C, 14, 17

HOLOTYPE: FMNH 190972 . Adult male collected on 04 June 2006; field number D.S. Balete 4160. Fresh tissues removed from the thigh and placed in DMSO buffer. The rest of the specimen was initially fixed in formalin, now preserved in ethyl alcohol with skull removed and cleaned. It is currently housed at FMNH, but will be transferred to PNM.

TYPE LOCALITY: Philippines: Luzon Island: Aurora Province: Dingalan Municipality : 0.9 km S, 0.3 km W Mt. Mingan peak, 1785 m elevation, 15.47390° N, 121.40066° E (fig. 1) .

MEASUREMENTS: Tables 3 and 4.

SPECIMENS EXAMINED (N = 23): Aurora Province, Dingalan Municipality, Mt. Mingan , 0.9 km S, 0.3 km W Mt. Mingan peak, 1785 m elevation ( FMNH 190970–190972 [holotype], 190973); 1.5 km S, 0.5 km W Mt. Mingan peak, 1681 m elevation ( FMNH 190974–190979 ) ; 1.8 km S, 1.0 km W Mt. Mingan peak, 1677 m elevation ( FMNH 190961–190969 ) ; 1.9 km S, 1.6 km W Mt. Mingan peak, 1476 m elevation ( FMNH 190980–190982 ) .

ETYMOLOGY: We name this species in honor of our colleague and friend Leonardo Co, who devoted his life to studying the plants of the Philippines and their medicinal uses, promoting conservation, improving the lives of his fellow Filipinos, and enhancing our knowledge of this unique and threatened flora.

DIAGNOSIS: A slender-bodied member of Soricomys , distinguished from congeners by the following combination of features: (1) larger body size; (2) longer, dark reddish-brown dorsal pelage, shorter and paler orange-brown ventrally; (3) relatively shorter tail; (4) wider interorbital region; (5) wider zygomatic plate; (6) longer incisive foramina; (7) shorter diastema; (8) longer postpalatal region; (9) longer maxillary molar row; (10) broader first upper molars; and (11) narrower incisor breadth at their tips.

DESCRIPTION AND COMPARISONS: The pelage of S. leonardocoi is dark grayish chestnut dorsally, pale grayish brown and shorter ventrally, without distinct patterning. The lips and rhinarium are medium gray (fig. 12C). Mystacial vibrissae are dark gray with pale tips that extend beyond the ears. The eyelids are dark gray surrounded by a narrow paler band covered with short, dark, grayish-brown fur. The dark gray ears are small, rounded, and covered with short, dark hairs. The front feet of S. leonardocoi are small, with long, slender digits bearing long, opaque claws with decurved tips, except the pollex, which is short and bears a nail. The dorsal surface is pigmented medium grayish brown, and the palmar surface and palmar pads, consisting of three small interdigitals and two larger pads (thenar and hypothenar), are paler and uniformly pigmented. The hind feet are long and slender, with long, slender digits bearing long, opaque claws. They are dorsally pigmented medium grayish brown, darker on the digits, and covered with grayish-brown fur; dark gray to pale grayish-brown ungual tufts extend to about three-quarters of the length of claws. The plantar surface is uniformly pigmented dark grayish brown; six plantar pads, consisting of four interdigitals, a thenar, and a hypothenar, are small relative to the plantar surface, and uniformly pigmented the same darkness as the plantar surface except slightly paler at the distal tips.

Soricomys leonardocoi is similar to congeners in overall body form, but most similar to S. musseri in most external features and body proportions (fig. 12, table 3; Rickart et al., 1998: fig. 10). It is distinguished from the latter by the following external features: (1) longer and larger body (shorter in S. musseri ); (2) absolutely and relatively longer hind foot with darkly pigmented plantar pads (absolutely and relatively shorter, with paler plantar pads); (3) longer, darker fur (shorter and pale yellowish brown); and (4) relatively shorter tail (longer). Soricomys leonardocoi is distinguished from S. kalinga by the following external characters (fig. 12C, table 3; Balete et al., 2006: fig. 3): (1) large body size overall (smaller in S. kalinga ); (2) relatively shorter tail (longer); and (3) relatively shorter hind foot (longer); and from S. montanus by: (1) longer body overall (shorter in S. montanus ); (2) longer, darker pelage (shorter and paler); (3) relatively shorter tail (longer); and (4) relatively shorter hind foot (longer).

The skull of S. leonardocoi , as in congeners, is smooth and the braincase is longer than wide, appearing rectangular in general outline. The rostrum is short and tapered. Laterally, the dorsal profile is nearly straight from the top of the skull to the tip of the rostrum. The nasals of S. leonardocoi are straight, and terminate near the level of the anterior edges of the premaxillae. The upper incisor root is enclosed in a slightly raised bony capsule within the premaxilla and terminates medially near the suture with the maxilla, opposite the dorsal opening of the small and narrow lachrymal canal. The opening of this canal slants caudad and its swollen outer wall conspicuously broadens the base of the rostrum. The zygomatic plate has a nearly straight, vertical anterior edge relative to the upper molar row. The zygomatic process of the squamosal is anchored posteriorly about 1 mm above the dorsal edge of the postglenoid foramen and attached higher laterally on the cranium. The tympanic hook of the squamosal is broadly tapered ventrad and slanted caudad. This broadening of the tympanic hook dorsally is coupled by the intrusion mediolaterally of a small bony mastoidal spur into the squamoso-mastoid foramen, resulting in a very narrow opening (fig. 17). A relatively large mastoid fenestra is near the posterior margin of the mastoid, opposite the small mastoid foramen along the occipital suture (fig. 17).

In ventral aspect of the skull, the incisive foramina of S. leonardocoi are small, round edged posteriad and smoothly tapered anteriad; they are slightly more than half the length of the diastema (fig. 17, table 4). The alisphenoid canal is small and narrow. It is positioned under the posterior edge of the thin pterygoid ridge, behind the short and narrow alisphenoid strut. The pterygoid ridge itself terminates posteriad at the juncture with the alisphenoid strut, opposite which a relatively wide pterygoid bridge extends over the foramen ovale to the anterior edge of the elongate middle lacerate foramen. The postglenoid vacuity is relatively spacious and appears rectangular due to its straight dorsal edge (domed in congeners), and an almost straight ventral edge formed by the periotic part of the petromastoid (fig. 17). The auditory bulla is relatively small and ventrolaterally inflated, obscuring as much as the anterior half of the petrosal in ventral view. Soricomys kalinga and S. montanus have a similar pattern of bullar inflation; it is less pronounced in S. musseri .

The cranial features of S. leonardocoi are similar to all congeners, but most similar to S. musseri (figs. 10, 11, table 4; Balete et al., 2006: figs. 4, 5; Rickart et al., 1998: figs. 8–10, 13, 14). However, subtle but consistent differences are evident between S. leonardocoi and S. musseri , and the following combination of features distinguishes the former from the latter: (1) slightly longer skull (shorter in S. musseri ); (2) shorter nasals (longer); (3) longer incisive foramina (shorter); (4) narrower interorbital region (broader); (5) narrower zygomatic breadth (broader); (6) broader zygomatic plate with nearly straight anterior edge (narrower with slightly concave anterior edge); (7) long and slender squamosal strut (shorter and broader); (8) larger squamoso-mastoid vacuity; (9) narrower alisphenoid strut (wider), and (10) narrower pterygoid bridge (wider). Soricomys leonardocoi is distinguished from S. kalinga by the following combination of cranial features (figs. 9–11, 14, 17, table 4; Balete et al., 2006: figs. 4, 5): (1) longer and larger skull (shorter, narrower skull in S. kalinga ); (2) dorsolaterally inflated cranium (lower and flatter braincase; (3) broader interorbit (narrower); 4) narrower squamoso-mastoid vacuity (larger); (5) shorter diastema (longer); and (6) longer postpalatal region (shorter); and from S. montanus by: (1) longer skull with inflated cranium (shorter and flatter in S. montanus ); (2) wider interorbital region (narrower); (3) narrower zygomatic breadth (wider); (4) wider zygomatic plate (narrower); (5) shorter and shallower rostrum (longer and deeper); (6) shorter diastema (longer); and (7) greater orbito-temporal length (shorter).

The incisors of Soricomys leonardocoi are small and have smooth anterior surfaces. The upper incisors emerge from the rostrum at a right angle (orthodont) and have yellowish-orange enamel. The ventral tips are nearly straight edged. In ventral view, the outline of each incisor is U-shaped deflected laterally, forming a deep, V-shaped gap along their posteromedial margin (fig. 9). The lower incisors are long and thinly pointed and have pale yellow enamel. The upper molars are small and narrow, but with low and sloping labial cusps that do not have corresponding convexity. The first upper molar is only slightly more than half as wide as it is long, and appears roughly rectangular in outline (especially in individuals with worn molars). The convex projection of cusps t1 and t4 forms a distinct, shallowly bilobed and broadly tapered lingual outline on M1. Cusp t3 appears to be present in the shallow and sloping labial edge of the coalesced laminar outline of the first row of M1, but is difficult to detect in most specimens with worn molars; t3 is undetectable on M2. Cusp t 9 in both M1 and M2 is barely detectable on the broad laminar outline on the third row. M3 is relatively large in relation to M1 and M2, with the broadly convex cusp t1 accounting for about a third of the occlusal surface of this molar.

The dentition of S. leonardocoi is closely similar to congeners, differing mainly in relative sizes and cuspidation pattern (figs. 9, 14, 17, table 4; Balete et al., 2006: fig. 6; Rickart et al., 1998: fig. 8). It is readily distinguishable from S. musser i by the following combination of dental features: (1) longer maxillary molar tooth row (shorter in S. musseri ); (2) broader M1 (narrower); and (3) narrower incisors at their tips (broader), and from S. kalinga and S. montanus by: (1) longer maxillary molar tooth row (shorter in S. kalinga and S. musseri ); (2) broader first upper molar, M1 (smaller); (3) greater palatal breadth at M1 (narrower); (4) greater labial breadth at M3 (narrower); and (5) narrower incisors at their tips (broader).

The mandible of S. leonardocoi is closely similar to congeners in general shape and placement of mental and mandibular foramina, differing mainly in relative size and shape of the processes (fig. 17, table 4; Balete et al., 2006: fig. 4; Rickart et al., 1998: fig. 13). The coronoid process is relatively short and broadly slanting to about two-thirds the length of the slender condyloid process. In contrast, the coronoid process of S. kalinga is about as long, but more robust than in the new species; it is more delicate in S. musseri (fig. 10). The angular process of S. leonardocoi is slender and narrowly tapered; it is robust and broadly tapered in S. kalinga and S. montanus ; slender, broadly angled and nearly straight edged dorsally in S. musseri .

DISTRIBUTION: Currently known only from the Mingan Mountains, in the Central Sierra Madre (fig. 1).

ECOLOGY: We found Soricomys leonardocoi in montane and mossy forest from 1476 m to 1785 m elevation (Balete et al., 2011). It appeared to be active both day and night, with almost equal numbers of diurnal and nocturnal/crepuscular captures (Balete et al., 2011). In contrast, S. kalinga , S. montanus , and S. musseri appeared to be predominantly diurnal (Balete et al., 2006, 2011; Duya et al., 2011; Rickart et al., 2011a; Balete and Heaney, unpubl. data). Individuals were significantly more frequently caught with earthworm bait than coconut bait, indicating vermivorous habits (Balete et al., 2011). Soricomy s kalinga had similar statistically significant response to earthworm bait; S. musseri also was similar, but the sample size was small (Balete et al., 2006; Duya et al., 2011; Rickart et al., 2011a). Females have two pairs of inguinal mammae, as do congeners. Four of nine females caught in June had large mammae, but none was pregnant or lactating. A single male caught in late May had scrotal testes, as did six of seven during June.

We documented six members of the Chrotomys Division to occur sympatrically with S. leonardocoi on Mt. Mingan: Apomys microdon , A. musculus , A. aurorae , A. minganensis , and Rhynchomys sp. ; another member of this clade, Chrotomys cf. mindorensis , occurred at ca. 100 m, in a reforestation site planted with exotic species of trees (table 11; Balete et al., 2011; Heaney et al., 2011). Crocidura grayi , Bullimus luzonicus , Phloeomys pallidus , and Rattus everetti also occurred sympatrically with S. leonardocoi on Mt. Mingan (Balete et al., 2011).

Figures

FIG. 9. View of the posterior edge of the upper incisors of A, Archboldomys luzonensis (FMNH 147172); B, A. maximus, n. sp. (FMNH 193531, holotype); C, Soricomys kalinga (FMNH 175555, holotype); D, Soricomys leonardocoi, n. sp. (FMNH 190972, holotype); E, Soricomys montanus, n. sp. (FMNH 188314, holotype); F, Soricomys musseri (FMNH 147176, holotype).