Lagidium ahuacaense, Ledesma, Karim J., Werner, Florian A., Spotorno, Angel E. & Albuja, Luis H., 2009

Ledesma, Karim J., Werner, Florian A., Spotorno, Angel E. & Albuja, Luis H., 2009, A new species of Mountain Viscacha (Chinchillidae: Lagidium Meyen) from the Ecuadorean Andes, Zootaxa 2126, pp. 41-57 : 47-51

Lagidium ahuacaense , sp. nov.

Holotype. Adult male, skin and skull with mandibles, MEPN 10237, collected by Danny Hidalgo on 22 March 2006. The skin is well preserved, except for one small hairless patch on the neck.

Variable Principal component

Eigenvalue 8.11 1.32 0.89 0.69 Variance [%] 62.35 10.15 6.88 5.34

Type locality. Cerro El Ahuaca, Parroquia Cariamanga, Canton Calvas, Loja Province, Ecuador (04º18΄2ʺS, 79º32΄47ʺW).

Distribution. Lagidium ahuacaense is known only from the type locality. Cerro El Ahuaca is a steep granite peak of inselberg nature situated 1 km from the town of Cariamanga. The species inhabits the entire altitudinal range of the peak (1,950–2,480 m) as evident from faecal pellets and feeding marks, but appears restricted to the immediate vicinity of extensive rocky surfaces ( Werner et al. 2006). A more detailed habitat description is provided by Werner et al. (2006).

Etymology. The specific epithet refers to Cerro El Ahuaca. Common names: Ecuadorean mountain viscacha (English); viscacha de montaña ecuatoriana (Spanish).

Diagnosis. This is a medium-sized species of Lagidium , with a brown-grey fur coloration of the dorsal area and yellowish-grey coloration ventrally. Ears are blackish with cream-colored fringes. Hands and feet bear black hairs, palms and soles are naked and of blackish color. Dorsally, the tail has long coarse hairs, maroon with some cream in coloration, while the bottom of the tail has short, blackish brown hairs. The tip of the tail is covered with long hairs. Vibrissae are mostly black.

Comparisons. In L. peruanum , fur coloration can vary from creamy buff to dark grey ( Meyen 1833; Pearson 1948). The holotype of L. ahuacaense is darker in color (dorsally and ventrally) than the dark grey individuals of L. peruanum examined for this study (n = 20), which were suffused with more light hairs. Moreover, no L. peruanum showed such dark (almost black) coloration on the dorsum of the feet as the new species. As in L. peruanum , fur color in L. viscacia is highly variable. Dark grey individuals from Patagonia present a more conspicuous dark dorsal line than L. ahuacaense . Populations of L. wolffsohni are known by their ochre coloration ( Canevari & Vaccaro 2007).

In dorsal view, L. ahuacaense has much more pronounced bending premaxillo-frontal sutures than L. peruanum ; a wider rostrum and a narrower interorbital constriction than L. viscacia and L. wolffsohni . In lateral view, the braincase of L. ahuacaense is much less arched (vaulted) than that of L. peruanum , and slightly less arched than that of L. viscacia and L. wolffsohni ; in addition, L. peruanum shows a slender jugal and L. wolffsohni exhibits somewhat longer paraoccipital processes, more separated from the bullae.

In ventral view, the posterior margin of the hard palate of L. peruanum is either smoothly squared or concave, with few individuals showing a rather poorly developed postpalatal process. The mesopterygoid fossa in L. peruanum and L. viscacia has less diverging sides than in L. ahuacaense . This fossa has parallel sides in L. wolffsohni , resembling a letter ‘U’. The basioccipital is relatively wider in L. peruanum than in L. ahuacaense . In L. viscacia and L. wolffsohni the basioccipital is less constricted by the bulla at its middle region and noticeably wider than in L. ahuacaense .

Measurements. External and craniodental measurements are listed in Table 1 and discussed below.

Description. Total length is 803 mm. Body pelage wooly and grayish brown (Smoke Gray 45). Tail long with coarse hairs. Anterior dorsal pelage shorter than posterior pelage. Dorsal fur grayish with buffy and black tints. Medial dorsal area has a black longitudinal stripe. Length of dorsal hairs variable, with mean length ranging from 24 mm in the anterior region to 45 mm in the posterior region of the body. Dorsal cover hairs with a grey basal band (Medium Neutral Gray 84), a dark grey medium band (Dark Neutral Gray 83), and a cream-colored distal band (Cream 54). Guard hairs longer than cover hairs with two bands, a thin grey basal band (Medium Neutral Gray 84) and a thick black apical band (Jet Black 89). Length of guard hairs variable, averaging from 24 mm on the anterior region to 45 mm on the posterior region. Pelage of head resembling dorsal hair but shorter. Mystacial vibrissae thick and long (18–147 mm) and primarily dark brown with few scattered white hairs. Superciliary vibrissae scarce, up to 71 mm in length, thick and dark brown. In the holotype, one thick, dark brown genal vibrissa present (54 mm in length). Ear length is 60 mm. Skin inside and outside of ears black, with abundant hairs on the upper basal area. Remainder outside of the ears covered with fine brown hairs bordered by white hairs, inside of ear sparsely covered with fine white hairs. Hairs in mentonian region, flanks of the body, sides of the throat and ventral region creamy white with a grey basal band (Medium Neutral Gray 84) and cream-colored white distal band (Cream 54). Fur of inguinal region ochre, with bands similar to those of ventral region. Length of ventral hairs 15–24 mm in the anterior region, 17–31mm in the central region, and 21–31 mm in the posterior region. Fore feet substantially shorter than hind feet (36 versus 85 mm). The four digits of fore- and hind feet each with a small and slightly curved claw of 4.0– 6.5 mm. Tips of fingers large, spherical and fleshy. Hand and foot have three black pads with small cream-colored spots. First interdigital pad of hand spherical, smaller than the two other pads; medial pad on foot larger than the others; thenar and hypothenar long ( Fig. 4 ).

Fur on fore feet primarily brown intermixed with few cream-colored hairs ( Fig. 5 ). Fur on hind feet composed of cream-colored hairs intermixed with brown hairs from base to middle of foot, and dark brown hairs from middle to tip of the foot. Tail 400 mm in length, with long (21–143 mm) coarse hairs dorsally and short (12.5–29 mm) coarse hairs ventrally. Hairs of tail tip longer than those on the rest of tail, reaching up to 150 mm in length. Hair coloration on the upper tail divided into three categories: (1) basal region similar in color to dorsal region; (2) hairs of middle region including distal tail vertebrae light brown and medium brown hairs intermixed with cream-colored hairs; (3) tip of tail dark reddish brown (Raw Umber 223). Ventral tail hairs uniformly blackish brown (Sepia 119).

Skull elongated and compact with long axis slightly curved and depression in the supraorbital region ( Fig. 6 ). Zygomatic arch relatively broad. Nasal bones slightly concave at the proximal region, curved and inflated toward the distal region. Lacrimal capsule well developed. Frontal bones constricted in the middle region (16.5 mm long). Frontal sinuses slightly inflated. Neither occipital external crest nor nuchal crest well developed. In contrast, occipital external protuberance well defined and most prominent posterior point of skull. In lateral view, posterior region of skull curved, nasal bones appear swollen. Premaxilla protrudes slightly beyond front of incisors. Zygomatic process broad in the posterior region. Tympanic bulla small (15.6 mm in length) and rounded at base with external auditory meatus point directed towards the superior region.

Post-glenoid foramen large and cone-shaped with tip directed towards back of skull. From the ventral view, foramen magnum prominent, with maximum diameter of 11.2 mm. Incisive foramina long and narrow, with a central crease that forms two indentations. Palate narrow in the anterior region and broader in the posterior region. Length of palate raised and extends to near M3. Pterigoid crest extends to posterior region of M2. Posterior margin of palate indented in the shape of a ’W‘. Mesopterygoid fossa deep. Oval foramen large (4.9 mm diameter); located at the posterior region and positioned lateral to pterygoid fossa.

Structure of mandible robust with a blunt coronoid process directed towards the posterior and exterior regions. Rear mandible of symphysis located at same level as procingulum of p4. Condyle mandibles long. Foramen mandible located at internal base of coronoid process.

Dental rows converge in anterior region. Teeth of holotype characterized by low crowns. Dental formula: I 1 /1, C 0/0, P 1/1, M 3/3, in total 20 teeth.

Incisors whitish, large and elongated. Anterior surfaces of teeth with grooves that extend over the entire length of teeth, but most apparent on upper incisors. Grooves of upper incisors yellowish. Tip of one of upper incisors of the holotype broken. Lower incisors distinctively beveled. Upper dental row, 19.95 mm in length. Molars with low crowns and of continuous growth. Each molar characterized by a flat crown with two transverse lamellae of enamel oriented diagonally to the extreme posterior lingual. P4 slightly larger than remainder teeth. Posterior lamella of M1 and M2 angled and curved towards posterior region, posterior lamellae of M3 form a straight right angle. Lower dental row, 18.1 mm in length, and converges in the anterior region, similar to upper row. Each molar with two transverse lamellae of enamel. Cingulum of p4 on the labial side with two prominent depressions, posterior depression more pronounced. In labial region of m1-m3, posterior lamellae more pronounced than those of the anterior region. Lingual region of m1-m3 with concave cingulum in the anterior lamella region; posterior region convex ( Fig. 6 ).

Figures

FIGURE 4. Plantar view of right hind foot (A) and right fore foot (B) of L. ahuacaense sp. nov. h = hypothenar pad, t = thenar pad; 1 – 3 = first through third interdigital pad. Scale bar = 10 mm.

FIGURE 5. Skin of the holotype of Lagidium ahuacaense sp. nov. (MEPN 10237). Scale bar = 100 mm.

FIGURE 6. Skull of the holotype of Lagidium ahuacaense sp. nov. (MEPN 10237). Scale bar = 10 mm.