Sauresia gracilis, Schools & Hedges, 2024

Schools, Molly & Hedges, Blair, 2024, A new forest lizard fauna from Caribbean islands (Squamata, Diploglossidae, Celestinae), Zootaxa 5554 (1), pp. 1-306 : 231-234

Sauresia gracilis sp. nov.

Slender Four-toed Forest Lizard

(Fig. 85)

Sauresia sepsoides — Schwartz & Henderson, 1988:162 (part).

Sauresia sepsoides — Schwartz & Henderson, 1991:463 (part).

Celestus sepsoides — Henderson & Powell, 2009:105 (part).

Celestus sepsoides — Hedges et al., 2019:17 (part).

Sauresia sepsoides — Schools & Hedges, 2021:231 (part).

Sauresia sepsoides — Landestoy et al., 2022: 205 (part).

Holotype. USNM 328852 , an adult from 10.3 km NW of Port Salut , Sud Department, Haiti, collected by S. Blair Hedges and Richard Thomas on 28 October 1984 (18.1419, -73.9711; 10 m).

Diagnosis. Sauresia gracilis sp. nov. has (1) a dorsal pattern of mottled/lineate, (2) head markings absent, (3) markings in the longitudinal paramedian area present, (4) dots arranged in bars in the lateral band absent, (5) a maximum SVL of 51.1 mm, (6) ventral scale rows, 103, (7) midbody scale rows, 36, (8) total lamellae on one hand, 18, (9) total strigae on ten scales, 100, (10) relative length of all digits on one hindlimb, 13.8 %, (11) relative distance between the angled subocular and mouth, 0.254 %, (12) relative eye length, 2.97 %, (13) relative forelimb length, 10.8 %, (14) relative ear width, 0.665 %, (15) relative rostral height, 1.90 %, (16) relative head length, 15.7 %, (17) relative mental width, 1.76 %, (18) relative postmental width, 2.76 %, (19) relative cloacal width, 7.18 %, (20) relative prefrontal width, 3.81 %, (21) relative largest supraocular width, 2.44 %, (22) relative longest finger length, 1.96 %, (23) relative distance between the ear and eye, 7.63 %, (24) relative head width, 67.6 %, (25) relative frontal width, 82.9 %, (26) relative nasal height, 0.998 %, (27) relative angled subocular height, 0.958 %, (28) relative distance between the eye and naris, 3.15 %, (29) relative canthal iii length, 1.82 %, (30) relative angled subocular width, 1.96 %, and (31) relative nasal length, 1.33 %. The species stem time is 4.21 Ma and no data are available to estimate the species crown time (Fig. 4).

Sauresia gracilis sp. nov. has a larger relative postmental width (2.76), relative cloacal width (7.18), and relative canthal iii length (1.82) than all other species of the genus. The only known specimen of S. gracilis sp. nov. is a small adult specimen, which may contribute to a bias towards larger measurements.

From Sauresia agramma sp. nov., we distinguish S. gracilis sp. nov. by the dorsal pattern (mottled/lineate versus absent), the adult SVL (51.1 versus 53.8–69.1), the ventral scale rows (103 versus 121–127), the midbody scale rows (36 versus 37–39), the total lamellae on one hand (18 versus 17), the total strigae on ten scales (100 versus 103–138), the relative rostral height (1.90 versus 1.92–2.12), the relative head length (15.7 versus 13.6– 15.2), the relative postmental width (2.76 versus 2.30–2.70), the relative cloacal width (7.18 versus 6.09–6.82), the relative longest finger length (1.96 versus 2.11–2.86), the relative head width (67.6 versus 69.7–74.6), the relative frontal width (82.9 versus 80.2–81.9), the relative width of canthal iii (1.82 versus 1.17–1.30), the relative angled subocular width (1.96 versus 2.07–2.47), and the relative nasal width (1.33 versus 1.36–1.57). From S. cayemitae sp. nov., we distinguish S. gracilis sp. nov. by the relative eye length (2.97 versus 2.14–2.90), the relative head length (15.7 versus 13.0–15.6), the relative postmental width (2.76 versus 2.27–2.51), the relative cloacal width (7.18 versus 5.59–6.24), the relative prefrontal width (3.81 versus 3.11–3.64), the relative largest supraocular width (2.44 versus 1.67–2.25), the relative longest finger length (1.96 versus 2.36–2.65), the relative distance between the ear and eye (7.63 versus 6.02–6.88), the relative head width (67.6 versus 68.5–77.1), the relative nasal height (0.998 versus 0.792 –0.951), and the relative width of canthal iii (1.82 versus 1.07–1.30). From S. habichi , we distinguish S. gracilis sp. nov. by the head markings (absent versus present), the adult SVL (51.1 versus 51.9–63.3), the ventral scale rows (103 versus 122–125), the midbody scale rows (36 versus 38–41), the relative length of digits on one hindlimb (13.8 versus 11.2–13.1), the relative distance between angled subocular and mouth (0.254 versus 0.000594 –0.201), the relative eye length (2.97 versus 2.22–2.95), the relative head length (15.7 versus 13.3–15.0), the relative postmental width (2.76 versus 2.11–2.34), the relative cloacal width (7.18 versus 5.86–6.68), the relative largest supraocular width (2.44 versus 1.96–2.23), the relative longest finger length (1.96 versus 2.26–2.71), the relative distance between the ear and eye (7.63 versus 6.64–7.30), the relative head width (67.6 versus 77.7–78.6), the relative frontal width (82.9 versus 71.8–77.5), and the relative width of canthal iii (1.82 versus 1.10–1.41). From S. manicula sp. nov., we distinguish S. gracilis sp. nov. by the dorsal pattern (mottled/lineate versus absent), the ventral scale rows (103 versus 121–129), the midbody scale rows (36 versus 37–38), and the total lamellae on one hand (18 versus 15–17). From S. pangnolae sp. nov., we distinguish S. gracilis sp. nov. by the dorsal pattern (mottled/lineate versus absent/irregular dots), the adult SVL (51.1 versus 53.8–66.7), the ventral scale rows (103 versus 104–119), the relative forelimb length (10.8 versus 11.4–12.6), the relative ear width (0.665 versus 0.681– 1.11), the relative head length (15.7 versus 13.0–15.4), the relative postmental width (2.76 versus 2.04–2.47), the relative cloacal width (7.18 versus 6.07–6.81), the relative longest finger length (1.96 versus 2.29–2.54), the relative distance between the ear and eye (7.63 versus 6.94–7.46), the relative head width (67.6 versus 70.8–78.2), the relative frontal width (82.9 versus 69.6–81.5), the relative width of canthal iii (1.82 versus 1.09–1.51), the relative angled subocular width (1.96 versus 2.16–2.39), and the relative nasal width (1.33 versus 1.38–1.62). From S. sepsoides , we distinguish S. gracilis sp. nov. by the ventral scale rows (103 versus 104–119), the relative postmental width (2.76 versus 1.92–2.61), the relative cloacal width (7.18 versus 5.11–6.77), and the relative width of canthal iii (1.82 versus 0.943–1.62). From S. synoria sp. nov., we distinguish S. gracilis sp. nov. by the dorsal pattern (mottled/lineate versus absent), the adult SVL (51.1 versus 53.5–72.0), the ventral scale rows (103 versus 114–127), the relative length of digits on one hindlimb (13.8 versus 10.5–12.3), the relative eye length (2.97 versus 2.47–2.94), the relative mental width (1.76 versus 1.21–1.70), the relative postmental width (2.76 versus 2.09–2.75), the relative cloacal width (7.18 versus 5.62–6.94), the relative prefrontal width (3.81 versus 3.01–3.30), the relative largest supraocular width (2.44 versus 1.57–1.91), the relative head width (67.6 versus 70.8–76.0), and the relative width of canthal iii (1.82 versus 0.943–1.31).

Description of holotype. USNM 328852. An adult; SVL 51.1 mm; tail nearly cylindrical, broken, 5.65 mm (11.1% SVL); axilla-to-groin distance 33.1 mm (64.8% SVL); forelimb length 5.54 mm (10.8% SVL); hindlimb length 10.4 mm (20.4% SVL); head length 8.03 mm (15.7% SVL); head width 5.43 mm (10.6% SVL); head width 67.6% head length; diameter of orbit 1.52 mm (2.97% SVL); horizontal diameter of ear opening 0.34 mm (0.665% SVL); vertical diameter of ear opening 0.25 mm (0.489% SVL); length of all toes on one foot 7.07 mm (13.8% SVL); shortest distance between angled subocular and lip 0.13 mm (0.254% SVL); shortest distance between the ocular and auricular openings 3.90 mm (7.63% SVL); longest finger length 1.00 mm (1.96% SVL); largest supraocular width 1.25 mm (2.45% SVL); cloacal width 3.67 mm (7.18% SVL); mental width 0.90 mm (1.76% SVL); postmental width 1.41 mm (2.76% SVL); prefrontal width 1.95 mm (3.82% SVL); frontal width 82.9% frontal length; nasal height 0.510 mm (0.998% SVL); angled subocular height 0.49 mm (0.959% SVL); shortest distance between the eye and naris 1.61 mm (3.15% SVL); canthal iii width 0.93 mm (1.82% SVL); angled subocular width 1.00 mm (1.96% SVL); nasal width 0.68 mm (1.33% SVL); rostral 1.90X as wide as high, visible from above, not in contact with nasals, in contact with 1 st supralabial and anterior internasal (left)/(right); anterior internasals are narrower than posterior ones; frontonasals and prefrontal fused into a single large plate with a straight posterior margin, much wider than long, bordered by posterior internasals, 1 st loreals, 1 st median oculars, 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 smaller than parietals and separating them, posteriorly touching the interoccipital, which is wider than long; parietal separated from supraoculars by 1 st and 2 nd temporals and frontoparietal (left)/(right); nasal single; nostril just posterior to suture between 1 st and 2 nd supralabials (left)/(right); 1 postnasal (left)/(right); 2 loreals (left)/ (right); 1 st loreal higher than wide (left)/(right), in contact with postnasal, posterior internasal, prefrontal/frontonasal complex, 1 st median ocular, canthal iii, 2 nd loreal, and 3 rd supralabial (left)/(right); 2 nd loreal shorter than 1 st, higher than wide (left)/(right), excluded from contact with supraocular by canthal iii (left)/(right); 2 nd loreal posteriorly bordering the lower preocular (left)/(right); canthal iii wider than high (left)/(right), contacting 1 st median ocular, anterior supraciliary, upper and lower preoculars, and 1 st and 2 nd loreals (left)/(right); 10 (left)/9 (right) median oculars, 1 st contacting the prefrontal (left)/(right); 1 upper preocular (left)/(right); an irregular anterior supraciliary (left)/(right); 6 lateral oculars (left)/(right); 5 temporals (left)/(right); 2 (left)/3 (right) suboculars; posterior subocular large and elongate (left)/(right); anterior subocular small (left)/(right); 10 supralabials (left)/(right), 6 to level below center of eye (left)/(right); 8 (left)/9 (right) infralabials, 5 (left)/6 (right) to level below center of eye; mental small, followed by a single, larger post mental; 4 pairs of enlarged chin shields; 1 st pair in contact with one another; 2 nd –4 th pairs separated by 1–2 scales; 99 transverse rows of dorsal scales from interoccipital to base of tail; 103 transverse rows of ventral scales from mental to vent; 36 scales around midbody; 4 digits; finger lengths 3>2>4>1; 5 (left)/6 (right) lamellae under longest finger; 18 total lamellae on one hand; toe lengths 3>2>4>1; 9 lamellae under longest toe (left)/(right); keelless and striate dorsal body and caudal scales; smooth ventral scales; 100 total strigae counted on ten scales.

FIGURE 85. (A–F) Sauresia gracilis sp. nov. (USNM 328852, holotype), SVL 51.1 mm.

Color (in alcohol): dorsal surface of head rusty brown with some darker brown mottling; lateral surfaces of head grading from rusty brown to dark cream with darker brown eye masks and spotting on the labial scales; dorsal surfaces of the body are rusty brown with darker areas in the center of scales, giving a lineate appearance that is most prominent around the neck; dorsal surface of tail the same as the body; lateral areas grade from dark brown to dark cream; dorsal surfaces of the limbs are dark brown; lateral and ventral areas of the limbs grading from dark brown to yellow-cream; ventral surfaces of the head, body, and tail are yellow-cream with some darker brown mottling especially under the chin and posteriorly, where it becomes the predominant color on the tail.

Variation. No other specimens are known. Measurements and other morphological data for the holotype are presented in Table 1.

Distribution. Sauresia gracilis sp. nov. is known only from the type specimen, which was collected on the southwestern coast of the Tiburon Peninsula of Haiti at an elevation of 10 m (Fig. 80). It has an extent of occurrence of ~ 40 km 2.

Ecology and conservation. The holotype of this species was collected during the day under an object in leaf litter. SBH has visited this region of the type locality (not necessarily the specific location) on many occasions in the intervening 40 years and has not found another specimen. It likely is very localized and secretive.

We consider the conservation status of Sauresia gracilis sp. nov. to be Critically Endangered B1ab(iii), based on IUCN Redlist criteria ( IUCN 2023). It faces a primary threat from habitat destruction resulting from agriculture and charcoaling. Haiti, in general, is heavily deforested with <1% of the nation’s primary forest remaining ( Hedges et al. 2018). Secondary threats to this species include predation from introduced predators, including the mongoose and black rats. Studies are needed to determine the health of any remaining populations and threats to the survival of the species. Captive-breeding programs should be undertaken, because eradication of introduced mammalian predators is currently not possible on large islands.

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

Etymology. The species name ( gracilis ) is a Latin nominative singular adjective meaning “slender,” alluding to the thin body shape and unusually low number of midbody scale rows in the holotype and only known representative of this species.

Remarks. Previously, this species was considered to be a member of Sauresia sepsoides . Additional material in museum collections currently catalogued as S. sepsoides from in or near the distribution of S. gracilis sp. nov. should be examined to determine if they represent additional material of S. gracilis sp. nov. This species is represented in our genetic dataset and the stem node places it outside of S. agramma sp. nov., S. manicula sp. nov., S. sepsoides , and S. synoria sp. nov. is significantly supported in our ML and Bayesian analyses. Based on our timetree (Fig. 4), S. gracilis sp. nov. diverged from its closest relative 4.21 Ma, consistent with typical species of vertebrates (> 0.7 Ma; Hedges et al. 2015). Our ASAP analysis also recognized S. gracilis sp. nov. as a distinct species.