Alinea pergravis ( Barbour 1921 ) Hedges, S. Blair & Conn, Caitlin E., 2012

Hedges, S. Blair & Conn, Caitlin E., 2012, A new skink fauna from Caribbean islands (Squamata, Mabuyidae, Mabuyinae) 3288, Zootaxa 3288 (1), pp. 1-244 : 54-56

Alinea pergravis ( Barbour 1921) comb. nov.

Providencia Skink

( Figs. 12D , 13D , 17 )

Mabuya pergravis Barbour, 1921:85 . Holotype: USNM 13875 (not examined), collected by the Albatross Expedition on Isla de Providencia, Department of San Andrés , Colombia, April 1884.

Mabuya pergravis — Dunn, 1936:536.

Mabuya mabouya pergravis —Dunn & Saxe, 1950:154.

Mabuya mabouya pergravis —Peters & Donoso-Barros, 1970:200.

Mabuya mabouya pergravis — Schwartz & Thomas, 1975:141.

Mabuya mabouya pergravis — MacLean et al., 1977:40 (part).

Mabuya mabouya pergravis — Schwartz & Henderson, 1988:150.

Mabuya mabouya pergravis — Schwartz & Henderson, 1991:457.

Mabuya pergravis — Miralles, 2006:1.

Material Examined (n = 6). Isla de Providencia , Colombia. MCZ R-14294 (paratype; no collector, specific locality, or date available) ; ANSP 25791–95 , collected by the Catherwood-Chaplin Expedition, no specific locality, 4 May 1948 .

Material not examined (n = 1). Isla de Providencia , Colombia. USNM 13875 (holotype), Albatross Expedition , Isla de Providencia, April, 1884 .

Diagnosis. Alinea pergravis is characterized by (1) maximum SVL in males, 87.7 mm; (2) maximum SVL in females, 90.9 mm; (3) snout width, 2.65–3.07% SVL; (4) head length, 17.5–19.2% SVL; (5) head width, 10.8– 12.8% SVL; (6) ear length, 1.54–1.84% SVL; (7) toe-IV length, 11.4–13.2% SVL; (8) prefrontals, two; (9) supraoculars, four; (10) supraciliaries, four; (11) frontoparietals, two; (12) supralabial below the eye, five (20%), six (80%); (13) nuchal rows, one (80%), two (20%); (14) dorsals, 62–63; (15) ventrals, 70–73; (16) dorsals + ventrals, 132–136; (17) midbody scale rows, 28–30; (18) finger-IV lamellae, 15–16; (19) toe-IV lamellae, 17–20;

(20) finger-IV + toe-IV lamellae, 32–36; (21) supranasal contact, Y; (22) prefrontal contact, N; (23) supraocular-1/ frontal contact, Y (80%), N (20%); (24) parietal contact, Y; (25) pale middorsal stripe, N; (26) dark dorsolateral stripe, N; (27) dark lateral stripe N; (28) pale lateral stripe, N; and (29) palms and soles, pale ( Tables 3–5).

Within the Genus Alinea , it is separated from all other species by having a higher number of dorsals (62–63 versus 54–61 in those other species) and combined dorsals and ventrals (dorsals + ventrals 132–136 versus 116– 130 in those other species). It also differs from A. berengerae and A. luciae in having more ventrals (70–73 versus 61–69 in those other species) and by having a larger auricular opening (ear length 1.54–1.84% SVL versus 1.43% SVL in A. berengerae and 0.983% SVL in A. luciae ). From A. lanceolata it differs, additionally, by having a longer toe (toe-IV length 11.4–13.2% SVL versus 9.25–10.8% SVL in A. lanceolata ). Alinea pergravis also differs from A. lanceolata and A. luciae in body shape (attenuate versus expanded at midbody) and ventral coloration (unpatterned versus ventral striping).

Description of material. Five adults (four male and one female) in excellent state of preservation, without injuries and with an abdominal slit. SVL 82.1–90.9 mm; tail length 116–164 mm (complete); HL 15.6–16.7 mm; HW 9.78–10.8 mm; SW 2.25–2.69 mm; EL 1.35–1.61 mm; and toe-IV length 10.4–10.8 mm; ear-openings large and round; toe length in the following order: I <II = V <III <IV.

Head scalation. Rostral wider than high, contacting first supralabials, nasals and supranasals. Paired supranasals in median contact, contacting anteriormost loreal. Frontonasal diamond-shaped, wider than long or approximately as wide as long, laterally in contact with anterior loreal scale. A pair of quadrilateral prefrontals, separated medially, and in contact with frontonasal, both anterior and posterior loreals, first supraciliary, first (and sometimes second) supraoculars, and frontal. Frontal roughly heptagonal, in contact with the first and/or second supraoculars and paired frontoparietals. Frontoparietals also in contact with parietals and interparietal. Interparietal tetragonal and lanceolate, separated from nuchals by parietals; parietal eye distinct. Parietals in contact with upper secondary and tertiary temporal scales. Four supraoculars, the second one being the longest and largest. Four supraciliaries, the second the longest. Nostril in posterior part of the nasal. A small postnasal, bordered by supranasal, anterior loreal and first supralabial. Anterior and posterior loreals rectangular with posterodorsal projection on latter. Two or three upper preoculars and two lower preoculars. Seven or eight supralabials, the fifth temporals, and three tertiary temporals; all imbricate, smooth, cycloid, not distinctly delimited from the scales on the nape and the sides of the neck. Seven or eight infralabials. Mental scale wider than long, posterior margin straight. Postmental scale and two or three pairs of adjoining chin shields in contact with anterior infralabials. First one or two pairs of chin shields in contact medially; second and/or third (and sometimes fourth) pair(s) separated by a smaller cycloid scale.

Body and limb scalation. One to two rows of paired nuchal scales. Other scales on nape similar to dorsals. On lateral sides of neck, scales slightly smaller. Dorsal scales cycloid, imbricate, smooth, 62–63 in a longitudinal row; ventrals similar to dorsals; 70–73 in a longitudinal row; 28–30 scales around midbody. No distinct boundaries between dorsals, laterals and ventrals. Scales on tail and limbs similar to dorsals, except smaller on limbs. Palmar and plantar regions with small tubercles, subequal in size and delimited by a surrounding region of flatter scales. Subdigital lamellae smooth, single, 15–16 under finger-IV and 17–20 under toe-IV. Preanal scales similar to ventrals. Enlarged median subcaudal scales on tail.

Pattern and coloration. Dorsal ground color pale grayish-green with medium-sized dark brown spots, distributed on body, tail, and limbs and on the head of one specimen ( ANSP 25791 ). Dark dorsolateral stripes absent. Dark lateral stripes absent; instead a series of discontinuous brown spots (not a stripe) extend from loreal region to region of forelimbs. Pale middorsal stripe absent, pale dorsolateral stripes, and pale lateral stripes absent. Ventral surface of body without pattern. Palmar and plantar surfaces pale, but with scattered brown flecks on ventral surface of some digits. No information is available on color in life of the holotype .

Distribution. This species is known only from the Caribbean island of Providencia, which lies about 240 km due east of the Nicaraguan coast ( Fig. 1 ). However, there are no specific localities recorded from that island, and therefore no distribution map is shown.

Ecology and conservation. An individual was first spotted on the ground and then went "high into" a tree (Dunn & Saxe 1950). The long toes, high digital lamellae counts, and gracile body shape of this species—the most attenuate species in the Subfamily Mabuyinae —agree with tree-climbing habits. Spondylurus fulgidus ( Jamaica) , another species known to have scansorial habits, comes close to Alinea pergravis in these traits ( Mabuya dominicana , although not known to be scansorial, has long digits and high lamellae counts). Also, the two species of Psychosaura gen nov. have similar traits and habits. One can only speculate that it found this open niche on Isla de Providencia after dispersing there from the Lesser Antilles, with selective pressures strongly favoring survival in trees. This species has not been recorded since 1950 (Dunn & Saxe 1950). The tropical rainforests of Isla de Providencia that once covered the island are "now almost completely destroyed", being replaced with agriculture (especially citrus fruits) and cattle farming ( World Wildlife Fund 2007). Heavy use of pesticides and expanding urbanization stemming from tourism are cited as severe threats to the biodiversity of the island ( World Wildlife Fund 2007).

Based on IUCN Redlist criteria ( IUCN 2011), we assess the conservation status of Alinea pergravis as Critically Endangered (CR A2ace). It faces a primary threat from habitat alteration and a secondary threat from introduced predators. Studies are needed to determine if the species still exists, the health of any remaining populations, and threats to the survival of the species. Captive breeding programs should be considered, if the species still exists. There have been no records of this species for 60 years.

Reproduction. No data on reproduction are available for this species.

Etymology. Not given in original description ( Barbour 1921). However, the species name is from the Latin per (very) and gravis (heavy), apparently in reference to the larger size of Alinea pergravis compared with a species (in the Genus Lygosoma ) that Barbour considered it to be its close relative. It is not an exceptionally large species of mabuyine skink and is not closely related to Lygosoma .

Remarks. The species was described ( Barbour 1921) based on four specimens collected in 1884 on the Albatross Expedition to what is now called Isla de Providencia (formerly "Old Providence Island"). The island is only 17 km 2. No diagnosis was given, and no ecological or collecting notes were provided. Later, Dunn (1936) lumped nearly all species of mabuyines known at that time from Caribbean islands into Mabuya mabouya , although he recognized Alinea pergravis as a distinct species based on its unique, pallid coloration and near absence of stripes. He had available the type series and one other specimen (USNM 78947). Later, Dunn and Saxe (1950) examined five additional specimens collected on the Catherwood-Chaplin expedition of 1948 and discussed pergravis ) rather than a distinct species. They noted similarities with skinks from the southern Lesser Antilles, especially from Barbados ( A. lanceolata ), and pointed out that the winds and current are favorable for dispersal from that region to Providencia. After examining A. pergravis , and before reading Dunn and Saxe (1950), we independently came to the same conclusion regarding the affinities of that species and its possible biogeographic origin. Miralles (2006a) examined two specimens of A. pergravis and briefly mentioned this species in his description of A. berengerae , noting a sample size of 20 individuals in his Table 1. However, that appears to be in error because he referred to Dunn and Saxe (1950), who took counts on the 10 known specimens. As far as we know, no other material of this species has become available. The local name for the species apparently is "Snakewaiting-boy" (Dunn & Saxe 1950).

Figures

FIGURE 1. Map of Caribbean region. Neotropical skinks occur, or once occurred, on the islands indicated.

FIGURE 12. Head scalation in species of the Genus Alinea (left, side view; right, dorsal view). (A) A. berengerae (UMMZ 127884, holotype); (B) A. lanceolata (BMNH 89.7.5.13); (C) A. luciae (BMNH 89.8.14.20); and (D) A. pergravis (MCZ R- 14294, paratype).

FIGURE 13. Representative patterns in species of the Genus Alinea (top, dorsal view; bottom, side view). (A) A. berengerae; (B) A. lanceolata; (C) A. luciae; and (D) A. pergravis.

FIGURE 17. Alinea pergravis, from Isla de Providencia, Colombia. (A–D) MCZ R-14294, paratype, Isla de Providencia (no specific locality).