Spondylurus culebrae, Hedges & Conn, 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 : 149-154

publication ID	https://doi.org/ 10.11646/zootaxa.3288.1.1
persistent identifier	https://treatment.plazi.org/id/39191A7F-079D-FF64-2DA9-EDE97DCFFAD4
treatment provided by	Felipe
scientific name	Spondylurus culebrae
status	sp. nov.

Treatment

Spondylurus culebrae sp. nov.

Culebra Skink

( Figs. 54C View FIGURE 54 , 55C View FIGURE 55 , 60 View FIGURE 60 )

Mabuya sloanii — Stejneger, 1904:608 (part).

Mabuya sloanii — Barbour, 1914:320 (part).

Mabuya sloanii — Schmidt, 1928:121 (part).

Mabuya sloanii —Barbour, 1930:105 (part).

Mabuya semitaeniatus — Grant, 1931:217 (part).

Mabuya semitaeniatus — Grant, 1932a:162 (part).

Mabuya mabouia — Barbour, 1935:129 (part).

Mabuya mabouya sloanii — Dunn, 1936:544 (part).

Mabuya mabouia — Barbour, 1937:147 (part).

Mabuya sloanii — Grant, 1937:504 (part).

Mabuya mabouya sloanei — Schwartz & Thomas, 1975:141 (part).

Mabuya mabouya sloanei — MacLean et al., 1977:29 (part).

Mabuya mabouya sloani — Rivero, 1978:71 (part).

Mabuya mabouya sloanei — Heatwole et al., 1981:34 (part).

Mabuya mabouya sloanei — Schwartz & Henderson, 1988:151 (part).

Mabuya mabouya sloanei — Schwartz & Henderson, 1991:457 (part).

Mabuya bistriata — Powell et al., 1996:82 (part).

Mabuya mabouya sloani — Rivero, 1998:394 (part).

Mabuya sloanii — Mayer & Lazell, 2000:883 (part).

Mabuya sloanii —Miralles, 2005:49 (part).

Mabuya sloanii — Henderson & Powell, 2009:293 (part).

Holotype. UMMZ 73823 View Materials , an adult male, collected April 1932 on Culebra, Puerto Rico, United States (no specific locality within Culebra) by Chapman Grant.

Paratypes (n = 49). Culebra, Puerto Rico. AMNH R-14005–06, K. P. Schmidt & B. A. Wall, no specific locality, 5 October 1919 ; UMMZ 73819–20 View Materials , UMMZ 73822–23 View Materials , UMMZ 73826 View Materials , UMMZ 239548–80 View Materials and 239582–

Diagnosis. Spondylurus culebrae sp. nov. is characterized by (1) maximum SVL in males, 88.0 mm; (2) maximum SVL in females, 97.6 mm; (3) snout width, 2.28–3.50% SVL; (4) head length, 16.0–21.6% SVL; (5) head width, 11.4–16.1% SVL; (6) ear length, 1.36–2.36% SVL; (7) toe-IV length, 8.42–12.9% SVL; (8) (2%); (13) nuchal rows, one (4%), two (88%), three (8%); (14) dorsals, 57–65; (15) ventrals, 60–70; (16) dorsals + ventrals, 121–134; (17) midbody scale rows, 30–36; (18) finger-IV lamellae, 13–16; (19) toe-IV lamellae, 14–19; (20) finger-IV + toe-IV lamellae, 28–34; (21) supranasal contact, Y (80%), N (20%); (22) prefrontal contact, N; (23) supraocular-1/frontal contact, Y (29%), N (71%); (24) parietal contact, Y (98%), N (2%); (25) pale middorsal stripe, Y; (26) dark dorsolateral stripe, Y; (27) dark lateral stripe, Y; (28) pale lateral stripe, Y; and (29) palms and soles, pale ( Tables 3–5).

Within the Genus Spondylurus , S. culebrae sp. nov. differs from S. caicosae sp. nov., S. fulgidus , S. haitiae sp. nov., S. macleani , S. magnacruzae sp. nov., S. martinae sp. nov., S. nitidus , S. powelli sp. nov., S. spilonotus , and S. turksae sp. nov. by having a higher dark dorsolateral stripe width/middorsal stripe width ratio (0.953–2.24 versus 0.115 –0.916 in those other species). It differs from S. anegadae sp. nov., S. macleani , and S. turksae sp. nov. by having dark dorsal spots posterior to the dark dorsolateral stripes (versus essentially no dorsal pattern posterior to the dark dorsolateral stripes in those other species). It differs from S. haitiae sp. nov. and S. lineolatus by having a longer head (head length 16.0–21.6% SVL versus 12.9–15.8% SVL in those other species). From S. anegadae sp. nov., it is separated by a plot of interparietal width versus SVL ( Fig. 57 View FIGURE 57 ). It is distinguished from S. fulgidus by having a higher number of combined dorsals and ventrals (121–134 versus 108–120 in S. fulgidus ). It is separated from S. lineolatus by having a higher number of midbody scale rows (30–36 versus 26–28). It differs from S. monae sp. nov. by having a higher, shorter rostral scale ( Fig. 61 View FIGURE 61 ). From S. monitae sp. nov., it differs by having straighter dark dorsolateral stripes (versus dark dorsolateral stripes that bow inward on the parietal scales). From S. semitaeniatus , it is distinguished by having longer total head scalation ( Fig. 62A View FIGURE 62 ). From S. sloanii , it is distinguished by having a relatively longer head and more finger-IV lamellae ( Fig. 62B View FIGURE 62 ).

The following frequency differences also distinguish Spondylurus culebrae sp. nov. from other species. It differs by having supranasal contact in 80% of specimens versus no contact in 81–100% of specimens belonging to S. martinae sp. nov., S. powelli sp. nov., and S. turksae sp. nov. It is distinguished from S. monitae sp. nov. by having a higher number of supralabial scales (supralabial six or seven below the eye in 84% of specimens versus supralabial five below the eye in S. monitae sp. nov.). Spondylurus culebrae sp. nov. tends to have more midbody scale rows (30–36) than S. nitidus (28–33); 78% of S. culebrae sp. nov. have 32 or more whereas 53% of S. nitidus have 30 or fewer. Spondylurus culebrae sp. nov. also tends to have more dorsals + ventrals (121–134) than S. nitidus (117–129); 88% of S. culebrae sp. nov. have 123 or more whereas 46% of S. nitidus have 122 or fewer. From S. sloanii , it differs by having more finger-IV + toe-IV lamellae (30–34 in 81% of S. culebrae sp. nov. versus 24–29 in 95% of S. sloanii ) and by having a greater separation of the prefrontals (frontal/frontonasal suture length 0.51–1.2% SVL in 84% of S. culebrae sp. nov. versus 0–0.38% SVL in 81% of S. sloanii ). Additionally, S. culebrae sp. nov. is a large species (maximum adult SVL 97.6 mm versus 63.7–95.5 mm in all others within Spondylurus except S. magnacruzae sp. nov. and S. spilonotus ).

Description of holotype ( Figs. 54C View FIGURE 54 , 60A–B, D View FIGURE 60 ). An adult male in excellent state of preservation, without injuries and with an abdominal slit. SVL 85.6 mm; tail length 50.2 mm (broken); HL 14.8 mm; HW 11.0 mm; SW 2.60 mm; EL 1.67 mm; and toe-IV length 8.30 mm; ear-opening average in size and round; toe length in the following order: I <II = V <III <IV.

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 supraoculars, and frontal. Frontal octagonal, semi-lanceolate, elongate, in contact with the first and second supraoculars and paired frontoparietals. Frontoparietals also in contact with parietals and interparietal. Interparietal tetragonal and acorn-shaped, separated from nuchals by parietals; parietal eye distinct. Parietals in contact with upper secondary and tertiary temporal scales. Four supraoculars (supraoculars three and four fused on the right), 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 squarish with posterodorsal projection on latter. One upper preocular and two lower preoculars. Eight supralabials, the sixth being the widest and forming the lower border of the eyelid. Three moderately enlarged scales behind eye comprising the postoculars; similar to temporal scales but smaller. One primary temporal, two secondary temporals, and three tertiary temporals; all imbricate, smooth, cycloid, not distinctly delimited from the scales on the nape and the sides of the neck. Eight infralabials. Mental scale wider than long, posterior margin straight. Postmental scale and one pair of adjoining chin shields in contact with anterior infralabials. First two pairs of chin shields in contact medially; third pair separated by a smaller cycloid scale.

Body and limb scalation. Two rows of nuchal scales, the first paired. Other scales on nape similar to dorsals. On lateral sides of neck, scales slightly smaller. Dorsal scales cycloid, imbricate, smooth, 59 in a longitudinal row; ventrals similar to dorsals; 63 in a longitudinal row; 33 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, 14 under finger-IV and 18 under toe-IV. Four preanals larger than adjacent ventral scales. No enlarged median subcaudal scales on tail.

Pattern and coloration. Dorsal ground color pale green with small-to-medium dark brown spots, uniformly distributed on body and tail. Dark dorsolateral stripes present, wide (2.85 mm), dark brown, extending from top of head to first third of body. Dark lateral stripes present, dark brown, extending from loreal region to last third of body. Pale middorsal stripe present, narrow (1.69 mm), pale green, extending from tip of snout to first third of body. Pale dorsolateral stripes present, whitish, extending from tip of snout to first third of body. Pale lateral stripes present, whitish, extending from below eye to midbody, bordered below by some dark spotting but not a narrow dark line. Ventral surface of body without pattern. Forelimbs and hindlimbs with distinct barring or mottling, darker on forelimbs. Palmar and plantar surfaces unpigmented. No information on color in life is available on the holotype.

Variation. In coloration and scalation, most specimens resembled the holotype ( Tables 4–5), except that dorsal ground color varied among shades of brown, gray, bluish-green, and green in adults and gray or tan in juveniles. In some specimens, only a few dark dorsal spots were present; in others, many dark dorsal spots were arranged in broken stripes extending the length of the body. The pale dorsolateral stripes differed in coloration between specimens but often appeared white or some shade of pale blue. In some specimens, the color of the pale middorsal stripe matched that of the pale dorsolateral stripes, but in others, the pale middorsal stripe was darker. Grant (1931) agreed, stating, “The median line on the head is as light as the white dorso-lateral line in some from Mona and Culebra islands,” but he noted cream-colored pale dorsolateral stripes in those specimens. Therefore, the bluishgreen coloration we observed probably resulted from preservative. Grant (1931) mentioned similar coloration between adults and juveniles but said that juvenile tails, in life, were lavender with white tips, something that we did not observe in a live juvenile S. culebrae sp. nov. ( Fig. 60C View FIGURE 60 ).

Distribution. The species is distributed on Culebra and the adjacent islet of Culebrita ( Fig. 10D View FIGURE 10 ). We tentatively assign the skinks from the islets of Cayo Luis Peña and Cayo Norte to S. nitidus , a species which is also sympatric with S. culebrae sp. nov. on Culebra.

Ecology and conservation. Grant (1931) found specimens among the cactus Opuntia "at sea level just above the beaches and among the rocks on the hills.” He also stated that they can be found inside houses. Culebra has a human population of ~2,000, and the major threats to the skink are introduced mammals, especially the rats. These introduced predators do not recognize the boundaries of the wildlife refuge on Culebra, and therefore the skinks are not actually protected. All of the original, virgin forest on Culebra has been destroyed, including that in the

Based on IUCN Redlist criteria ( IUCN 2011), we assess the conservation status of Spondylurus culebrae sp. nov. as Critically Endangered (CR A2ace). It faces a primary threat from predation by introduced mammals, including black rats, and a secondary threat from habitat alteration. Studies are needed to determine the health of remaining populations, and threats to the survival of the species. Captive breeding programs should be considered.

Reproduction. Eleven females (78.6–97.6 mm SVL) contained 2–5 (mean = 3.55) developing young. The dates of collection for those specimens were 1 February 1932, March 1932, April 1932, and August 1936.

Etymology. The species name ( culebrae ) is a feminine genitive singular noun referring to the distribution of the species on the island of Culebra.

Remarks. Wiegmann (1837) described Euprepes semitaeniatus (= Spondylurus semitaeniatus ), but its locality was unknown. Although color differences between S. semitaeniatus and S. sloanii were noted by Stejneger (1904) and Schmidt (1928), S. semitaeniatus was later lumped with S. sloanii because of a lack of other distinct morphological differences. Grant (1931) resurrected the name S. semitaeniatus for the skinks on Mona and Culebra based on the color and pattern of his specimens, noting a number of differences between them and skinks from other islands. However, a few years later ( Grant 1937) he treated them again as S. sloanii , without comment. As will be shown below, S. sloanii and S. semitaeniatus are both valid species, distinct from S. culebrae sp. nov. and restricted to the Virgin Islands. Although the range of S. sloanii is only ~ 10 km from that of S. culebrae sp. nov. whereas S. monitae sp. nov. is ~ 300 km from both (and separated by the entire island of Puerto Rico, where S. nitidus occurs), the three species show similar levels of sequence divergence ( Fig. 5–6 View FIGURE 5 View FIGURE 6 ), lending additional support to their recognition as distinct species.

One specimen of the long series of skinks (n = 51) from Culebra, UMMZ 239581, collected by Grant in April 1932, appears to belong to S. nitidus based on scalation and the non-overlapping pattern character noted above. It has a dark dorsolateral stripe width/middorsal stripe width ratio of 0.742 versus 0.953–2.24 in S. culebrae sp. nov. and 0.292 –0.619 in S. nitidus . It has 118 dorsals + ventrals, consistent with S. nitidus (117–129) but nonoverlapping with S. culebrae sp. nov. (121–134). It also has 30 midbody scale rows, typical of S. nitidus but at the low extreme of S. culebrae sp. nov. (84% of S. culebrae sp. nov. with> 30 midbody scale rows). Specimens from Cayo Luis Peña (UMMZ 73827) and Cayo Norte (UPRRP 5055), small islets off of Culebra, similarly agree with S. nitidus and not S. culebrae sp. nov. It seems remarkable that these two species occur on and around the small island of Culebra, given the taxonomic history of Caribbean island skinks. But when one considers the reduction in abundance, and likely extinctions, caused by the mongoose, the coexistence of multiple species—as also documented in the Virgin Islands and Windward Islands—should not be surprising. Genetic data from S. nitidus , including those from Puerto Rico and Culebra, would help confirm this apparent case of sympatry in two very closely related species.