Caribicus darlingtoni ( Cochran 1939 )

Schools, Molly & Hedges, Blair, 2024, A new forest lizard fauna from Caribbean islands (Squamata, Diploglossidae, Celestinae), Zootaxa 5554 (1), pp. 1-306 : 30-34

Caribicus darlingtoni ( Cochran 1939)

Hispaniolan Striped Forest Lizard

(Fig. 7–8)

Celestus darlingtoni Cochran, 1939:2 . Holotype: MCZ R-44374, collected by Philip J. Darlington, Jr. from Valle Nuevo , La Vega Province, Dominican Republic, in August 1938 (18.809, -70.682; 2,290 m).

Celestus darlingtoni — Cochran, 1941:253.

Celestus darlingtoni — Schwartz & Henderson, 1991:372.

Celestus darlingtoni — Powell et al., 1999:105.

Celestus darlingtoni — Hedges et al., 2019:17.

Caribicus darlingtoni — Schools & Hedges, 2021:218.

Caribicus darlingtoni — Landestoy et al., 2022:204.

Material examined (n=17). DOMINICAN REPUBLIC. La Vega. MALT 00988–91 , 00997 , Miguel A. Landestoy T., 16.9 km SSE of Constanza ; MCZ R-44374–76, Philip J. Darlington, Jr., Valle Nuevo , 1–31 August 1938 ; USNM 107563–4 , Valle Nuevo, SE of Constanza, Cordillera Central, August 1938 ; USNM 328801–4 , S. Blair Hedges and Richard Thomas, 36.7 km SE of Constanza , via old road to San Jose de Ocoa, 6 August 1983 ; USNM 328805–7 , S. Blair Hedges and Richard Thomas, ca. 37 km SE of Constanza , via new road to San Jose de Ocoa, 13 July 1986 .

Diagnosis. Caribicus darlingtoni has (1) a lineate dorsal pattern, (2) head markings absent/present, (3) markings in the longitudinal paramedian area absent/present, (4) dots arranged in bars in the lateral band absent/present, (5) an adult SVL of 61.1–74.9 mm, (6) ventral scale rows, 69–92, (7) midbody scale rows, 33–39, (8) total lamellae on one hand, 33–39, (9) total strigae on ten scales, 90–120, (10) relative length of all digits on one hindlimb, 26.1– 31.9 %, (11) relative distance between the angled subocular and mouth, 0.768–1.13 %, (12) relative eye length, 3.45–3.92 %, (13) relative forelimb length, 20.2–23.3 %, (14) relative ear width, 1.17–1.85 %, (15) relative rostral height, 1.76–2.22 %, (16) relative head length, 17.4–20.0 %, (17) relative mental width, 2.05–2.52 %, (18) relative postmental width, 2.70–3.21 %, (19) relative cloacal width, 7.08–8.48 %, (20) relative prefrontal width, 4.51–7.09 %, (21) relative largest supraocular width, 2.70–3.12 %, (22) relative longest finger length, 4.86–6.14 %, (23) relative distance between the ear and eye, 6.83–8.58 %, (24) relative head width, 72.5–93.4 %, (25) relative frontal width, 74.3–80.7 %, (26) relative nasal height, 1.14–1.45 %, (27) relative angled subocular height, 0.810–1.05 %, (28) relative distance between the eye and naris, 4.38–5.61 %, (29) relative canthal iii length, 1.68–2.03 %, (30) relative angled subocular width, 2.24–2.81 %, and (31) relative nasal length, 1.63–1.92 %. The species stem time is 6.83 Ma and the species crown time is 0.47 Ma (Fig. 4).

Caribicus darlingtoni differs from all other species of the genus in having a lineate dorsal pattern. This species has the lowest counts in the genus of total lamellae on one hand (33–39) and total strigae on ten scales (90–120). Caribicus darlingtoni has the smallest SVL (61.1–74.9), relative distance between the angled subocular and mouth (0.768–1.13), relative cloacal width (7.08–8.48), and the relative frontal width (74.3–80.7) of the genus. This species also has the largest relative mental width (2.05–2.52) and relative nasal height (1.14–1.45) of any species of Caribicus . Notably, Caribicus darlingtoni has a smaller SVL than other observed members of the genus by at least 152 mm.

FIGURE 7. (A–F) Caribicus darlingtoni (MCZ R-44374, holotype), SVL 66.0 mm.

From Caribicus anelpistus , we distinguish C. darlingtoni by the dorsal pattern (lineate versus bands), the adult SVL (61.1–74.9 versus 279), the total lamellae on one hand (33–39 versus 43–48), the total strigae on ten scales (90–120 versus 471), the relative length of digits on one hindlimb (26.1–31.9 versus 24.6), the relative distance between angled subocular and mouth (0.768–1.13 versus 1.24), the relative ear width (1.17–1.85 versus 1.15), the relative head length (17.4–20.0 versus 23.8), the relative mental width (2.05–2.52 versus 1.82), the relative postmental width (2.70–3.21 versus 3.87), the relative cloacal width (7.08–8.48 versus 10.8), the relative largest supraocular width (2.70–3.12 versus 2.31), the relative distance between the ear and eye (6.83–8.58 versus 10.6), the relative frontal width (74.3–80.7 versus 89.3), the relative nasal height (1.14–1.45 versus 1.11), the relative angled subocular height (0.810–1.05 versus 1.89), and the relative width of canthal iii (1.68–2.03 versus 1.64). From C. warreni , we distinguish C. darlingtoni by the dorsal pattern (lineate versus absent/bands), the adult SVL (61.1–74.9 versus 227–300), the total lamellae on one hand (33–39 versus 41–47), the total strigae on ten scales (90–120 versus 458–500), the relative distance between angled subocular and mouth (0.768–1.13 versus 1.51–1.57), the relative mental width (2.05–2.52 versus 1.46–1.87), the relative cloacal width (7.08–8.48 versus 9.33–10.3), the relative longest finger length (4.86–6.14 versus 3.41–4.71), the relative frontal width (74.3–80.7 versus 82.3), the relative nasal height (1.14–1.45 versus 1.06), and the relative nasal width (1.63–1.92 versus 1.49).

Description of holotype. MCZ R-44374. An adult; SVL 66.0 mm; tail nearly cylindrical, broken in life near tip, regenerated, 56.7 mm (85.9% SVL); axilla-to-groin distance 32.7 mm (49.5% SVL); forelimb length 15.4 mm (23.3% SVL); hindlimb length 21.7 mm (32.9% SVL); head length 12.7 mm (19.2% SVL); head width 9.80 mm (14.8% SVL); head width 77.2% head length; diameter of orbit 2.43 mm (3.68% SVL); horizontal diameter of ear opening 0.83 mm (1.26% SVL); vertical diameter of ear opening 0.66 mm (1.00% SVL); length of all toes on one foot 19.0 mm (28.8% SVL); shortest distance between angled subocular and lip 0.66 mm (1.00% SVL); shortest distance between the ocular and auricular openings 5.66 mm (8.58% SVL); longest finger length 4.05 mm (6.14% SVL); largest supraocular width 1.78 mm (2.70% SVL); cloacal width 5.08 mm (7.70% SVL); mental width 1.35 mm (2.05% SVL); postmental width 1.99 mm (3.02% SVL); prefrontal width 4.68 mm (7.09% SVL); frontal width 80.7% frontal length; nasal height 0.84 mm (1.27% SVL); angled subocular height 0.57 mm (0.864% SVL); shortest distance between the eye and naris 2.99 mm (4.53% SVL); canthal iii width 1.11 mm (1.68% SVL); angled subocular width 1.84 mm (2.79% SVL); nasal length 1.26 mm (1.91% SVL); rostral width 2.22X as wide as high, visible from above (missing), not in contact with nasals, in contact with 1 st supralabial (missing), and anterior internasal (missing) (left)/(right); anterior internasals are narrower than posterior ones; a pair of prefrontals, slightly smaller than the frontonasal; frontonasal quadrilateral, bordered by posterior internasals, prefrontal, and the frontal; frontal longer than wide; a pair of frontoparietals, separated by the posterior prolongation of the frontal and the interparietal plate; interparietal plate approximately the size of parietals and separating them, posteriorly touching the interoccipital, which is wider than long; parietal separated from supraoculars by 1 st temporals and frontoparietal (left)/(right); nasal single; nostril just posterior to suture between 1 st and 2 nd supralabials (left)/above suture between 1 st and 2 nd supralabials (right); 1 postnasal (left)/(right); 2 loreals (left)/(right); 1 st loreal higher than wide (left)/(right), in contact with postnasal, posterior internasal, frontonasal, 1 st median ocular, canthal iii, 2 nd loreal, and 3 rd and 4 th supralabials (left)/(right); 2 nd loreal shorter than 1 st, approximately as high as wide (left)/(right), excluded from contact with supraocular by canthal iii (left)/(right); final loreal posteriorly bordering the upper and lower preoculars (left)/(right); canthal iii wider than high (left)/(right), contacting 1 st median ocular, anterior supraciliary, upper preocular, and 1 st and 2 nd loreals (left)/(right); 8 (left)/9 (right) median oculars, 1 st contacting the prefrontal (left)/(right); 1 upper preocular (left)/(right); an irregular anterior supraciliary (left)/(right); 5 lateral oculars (left)/(right); 5 temporals (left)/(right); 2 suboculars (left)/(right); posterior subocular large and elongate (left)/(right); anterior subocular small (left)/(right); 10 supralabials (left)/(right), 6 (left)/6–7 (right) to level below center of eye; 9 infralabials (left)/(right), 5 (left)/6–7 (right) to level below center of eye; mental small, followed by a single, slightly larger postmental; 4 pairs of enlarged chin shields; 1 st pair in contact with one another; 2 nd –4 th pairs separated by 1–3 scales; 84 transverse rows of dorsal scales from interoccipital to base of tail; 92 transverse rows of ventral scales from mental to vent; 37 scales around midbody; 5 digits; finger lengths 3>4>2>5>1; 10 lamellae under longest finger (left)/(right); 38 total lamellae on one hand; toe lengths 4>3>5>2>1; 14 (left)/15 (right) lamellae under longest toe; keelless and striate dorsal body and caudal scales; smooth ventral scales; 111 total strigae counted on ten scales.

Color (in alcohol): dorsal surface of head medium brown with darker brown areas on scale borders; lateral surfaces of head grading from medium brown to gray-tan ventrally with irregular brown spots and darker brown eye masks; dorsal surfaces of the body are pale brown with approximately 10 dark brown dorsal stripes, the central two of which are not continuous; dorsal surface of tail same as body with a continuation of the stripes; lateral areas are the same dark brown of the dorsal stripes, heavily interspersed with cream spots grading to gray-tan; dorsal surfaces of the limbs are dark brown with pale dots; lateral and ventral areas of the limbs fade to muted brown with the same pattern as the dorsal areas; ventral surfaces of the head, body, and tail are pearl gray with pale brown markings that fade closer to the tail.

Variation. The examined material resembles the pattern of the holotype closely with dark lines extending down their dorsums. USNM 107564 is unique in lacking both a black outline on the head scales and longitudinal paramedian lines. The lateral areas of the examined material range from being patternless to mottled to having paler dots. Measurements and other morphological data for the holotype and other examined material are presented in Table 1.

Distribution. Caribicus darlingtoni is distributed in the Cordillera Central, Dominican Republic at elevations of 1360–2500 m (Fig. 5).

FIGURE 8. Caribicus darlingtoni (USNM 328807, SBH 161688), in life. From ca. 37 km SE Constanza on road to San Jose de Ocoa, La Vega Province, Dominican Republic. Photo by SBH.

Ecology and conservation. This species is often found in high, moist, well-drained areas of pine forests, often near bogs ( Schwartz & Henderson 1991). These lizards have reportedly been collected from under rocks, under bark, from the ruins of buildings, and from piles of boards and lumbering slash in sawdust at sawmill sites ( Schwartz & Incháustegui 1976; Schwartz & Henderson 1991). S. Blair Hedges (SBH) and Richard Thomas collected animals under rocks and logs 37 km (by road) SE of Constanza (18.7465, -70.6114) in 1983 and 1986. The species Panolopus marcanoi is found in similar situations and localities, with the type series of P. marcanoi originally assumed to be Caribicus darlingtoni ( Schwartz & Incháustegui 1976) . Schwartz & Incháustegui (1976) reported that individuals of this species occurred in more open areas than P. marcanoi and that they would burrow in the grass and leaf litter to escape capture. Schwartz & Incháustegui (1976) also commented that even in the cooler months of December and January, this species was active by midmorning.

The IUCN Redlist ( IUCN 2023) considers the conservation status of Caribicus darlingtoni to be Endangered B1ab(iii) due to its “limited distribution (with an extent of occurrence of 2,782 km 2),a severely fragmented population, and ongoing threats from agriculture expansion, wildfires due to anthropogenic causes and wood extraction.” The introduced mongoose and black rats are probably additional threats. Studies are needed to determine the health of remaining populations and more thoroughly assess threats to the survival of the species.

Reproduction. Ovoviviparous. Litter size, two, based on two females, one female weighing 1.9 g ( SBH, field data) .

Etymology. Named after Dr. Philip Jackson Darlington, Jr., the collector of the type specimen.

Remarks. Whereas the original description of this species ( Cochran 1939) is not detailed, Cochran (1941) gave a more expanded description. Underwood (1959) speculated that Caribicus darlingtoni represented the most “isolated” form of many of the Antillean species (not including Celestus microblepharis , Diploglossus delasagra , and Diploglossus pleii , which he placed in their own group). Prior to Schools & Hedges (2021), this species was never placed in a phylogenetic group with the large diploglossids ( C. anelpistus and C. warreni ), although Hass et al. (2001) found it to be close to C. warreni in immunological distance.

Caribicus darlingtoni is included in our genetic dataset and has significant support in both Bayesian and ML likelihood analyses at the crown node of the species and the stem node that identifies it as the closest relative of C. warreni . Based on our timetree (Fig. 4), C. darlingtoni diverged from its closest relative 6.83 Ma, consistent with typical species of vertebrates (> 0.7 Ma; Hedges et al. 2015). Caribicus darlingtoni was recognized as a distinct species by our ASAP analysis.