Panolopus hylonomus ( Schwartz 1964 )

Schools, Molly & Hedges, Blair, 2024, A new forest lizard fauna from Caribbean islands (Squamata, Diploglossidae, Celestinae), Zootaxa 5554 (1), pp. 1-306 : 165-169

Panolopus hylonomus ( Schwartz 1964)

Southeastern Smooth-scaled Forest Lizard

(Fig. 61–62)

Diploglossus curtissi hylonomus Schwartz, 1964:49 . Holotype: MCZ R-77160, collected by Albert Schwartz, Jr. and Richard Thomas from 0.5 mi. N. Boca de Yuma on 30 August 1963 (18.383, -68.609; 28 m).

Celestus curtissi hylonomus — Schwartz & Henderson, 1988:98.

Celestus curtissi hylonomus — Schwartz & Henderson, 1991:371.

Celestus curtissi hylonomus — Hedges et al., 2019:17.

Celestus curtissi hylonomus — Schools & Hedges, 2021:214.

Material examined (n=12). DOMINICAN REPUBLIC. AMNH 49771 , William G. Hassler, at caves near Rio Chavon , E of La Romana, 30 July 1935 . Distrito Nacional. AMNH 92799 , D. C. Leber, 7 mi E Boca Chica , 14 June 1963 . La Altagracia. KU 226274 , 0.5 mi NW Boca de Yuma , 30 August 1963 ; KU 226275–6 , 4 mi SE San Rafael del Yuma , 30 August 1963 ; KU 226281–2 , Juanillo, 18 August 1969 ; KU 226387 , 1.2 km SSW Punta Cana , 25 November 1971 ; MCZ R-75028–9, Clayton E. Ray, Robert Ross Allen, Juanillo, 29 March 1963 ; USNM 259954 , “Caldera” Pigeon shooting camp on Lagoon E of Punta Palmillas , 18 February 1965 . La Romana. MCZ R-77160, Albert Schwartz, Jr., Richard Thomas, 0.5 mi. N. Boca de Yuma, 30 August 1963 .

Diagnosis. Panolopus hylonomus has (1) a dorsal pattern of absent/irregular flecks, (2) head markings absent, (3) markings in the longitudinal paramedian area absent/present, (4) dots arranged in bars in the lateral band absent, (5) an adult SVL of 59.3–76.5 mm, (6) ventral scale rows, 80–97, (7) midbody scale rows, 33–39, (8) total lamellae on one hand, 34–47, (9) total strigae on ten scales, 169–222, (10) relative length of all digits on one hindlimb, 22.8– 28.2 %, (11) relative distance between the angled subocular and mouth, 0.424 –0.873 %, (12) relative eye length, 2.78–3.72 %, (13) relative forelimb length, 17.1–20.7 %, (14) relative ear width, 0.902–2.08 %, (15) relative rostral height, 1.72–2.28 %, (16) relative head length, 15.1–18.5 %, (17) relative mental width, 1.63–2.11 %, (18) relative postmental width, 2.67–2.89 %, (19) relative cloacal width, 7.98–8.57 %, (20) relative prefrontal width, 4.23–4.87 %, (21) relative largest supraocular width, 2.65–2.90 %, (22) relative longest finger length, 4.47–5.27 %, (23) relative distance between the ear and eye, 6.78–8.05 %, (24) relative head width, 73.8–76.4 %, (25) relative frontal width, 64.0–74.5 %, (26) relative nasal height, 0.961–1.37 %, (27) relative angled subocular height, 0.690–1.13 %, (28) relative distance between the eye and naris, 4.03–4.98 %, (29) relative canthal iii length, 1.95–2.03 %, (30) relative angled subocular width, 1.61–2.75 %, and (31) relative nasal length, 1.48–2.01 %. The species stem time is 0.85 Ma and no data are available to estimate the species crown time (Fig. 4).

We distinguish Panolopus hylonomus from the other species of Panolopus based on a complex of traits. From Panolopus aenetergum , we distinguish P. hylonomus by the dorsal pattern (absent/irregular flecks versus irregular dots), the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 83.0– 92.0), the total strigae on ten scales (169–222 versus 267), the relative postmental width (2.67–2.89 versus 2.62), the relative cloacal width (7.98–8.57 versus 7.60), the relative prefrontal width (4.23–4.87 versus 4.15), the relative largest supraocular width (2.65–2.90 versus 2.49), the relative distance between the ear and eye (6.78–8.05 versus 8.40), the relative frontal width (64.0–74.5 versus 88.2), and the relative width of canthal iii (1.95–2.03 versus 1.86). From P. aporus , we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present) and the adult SVL (59.3–76.5 versus 77.8–100). From P. chalcorhabdus , we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present), the relative length of digits on one hindlimb (22.8–28.2 versus 31.3–36.0), and the relative longest finger length (4.47–5.27 versus 5.29–6.97). From P. costatus , we distinguish P. hylonomus the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 83.6–107), the total lamellae on one hand (34–47 versus 49–58), the relative length of digits on one hindlimb (22.8–28.2 versus 31.5–37.8), the relative longest finger length (4.47–5.27 versus 5.53–6.66), the relative distance between the eye and naris (4.03–4.98 versus 5.08–5.50), and the relative width of canthal iii (1.95–2.03 versus 1.82–1.90). From P. curtissi , we distinguish P. hylonomus by the relative width of canthal iii (1.95–2.03 versus 1.75–1.93). From P. diastatus , we distinguish P. hylonomus by the relative largest supraocular width (2.65–2.90 versus 1.88–2.57). From P. emys , we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 99.0–113), the total strigae on ten scales (169–222 versus 238–311), and the relative length of digits on one hindlimb (22.8–28.2 versus 28.9–35.2). From P. lanceolatus sp. nov., we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 78.5–104), the relative length of digits on one hindlimb (22.8–28.2 versus 28.4–35.9), and the relative postmental width (2.67–2.89 versus 2.36–2.66). From P. lapierrae sp. nov., we distinguish P. hylonomus by the total strigae on ten scales (169–222 versus 228–231), the relative head width (73.8–76.4 versus 77.7–78.1), the relative frontal width (64.0–74.5 versus 77.6–79.0), the relative distance between the eye and naris (4.03–4.98 versus 5.21), and the relative width of canthal iii (1.95–2.03 versus 1.54–1.86). From P. leionotus , we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 86.3–105), the relative largest supraocular width (2.65–2.90 versus 1.94–2.50), and the relative width of canthal iii (1.95–2.03 versus 1.55–1.89). From P. marcanoi , we distinguish P. hylonomus by the dorsal pattern (absent/irregular flecks versus irregular dots/dots in chevrons), the head markings (absent versus present), and the dots arranged in bars in the lateral areas (absent versus present). From P. melanchrous , we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 93.2–124), the relative length of digits on one hindlimb (22.8–28.2 versus 30.7–41.3), the relative longest finger length (4.47–5.27 versus 5.76–7.09), the relative nasal height (0.961–1.37 versus 0.897 –0.952), and the relative width of canthal iii (1.95–2.03 versus 1.67–1.94). From P. neiba , we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 77.9–102), the relative length of digits on one hindlimb (22.8–28.2 versus 29.5–36.6), and the relative longest finger length (4.47–5.27 versus 5.61–6.66). From P. nesobous , we distinguish P. hylonomus by the dorsal pattern (absent/irregular flecks versus irregular dots/dots in series), the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 82.3–108), the total lamellae on one hand (34–47 versus 50–59), the relative length of digits on one hindlimb (22.8–28.2 versus 35.1), the relative forelimb length (17.1–20.7 versus 23.3–25.1), the relative longest finger length (4.47–5.27 versus 6.19–6.33), the relative frontal width (64.0–74.5 versus 60.8–63.5), and the relative distance between the eye and naris (4.03–4.98 versus 5.62–5.73). From P. oreistes , we distinguish P. hylonomus by the dorsal pattern (absent/irregular flecks versus irregular dots/dots in series/dots in chevrons), the dots arranged in bars in the lateral areas (absent versus present), the adult SVL (59.3–76.5 versus 77.3–103), the relative length of digits on one hindlimb (22.8–28.2 versus 31.2–40.1), and the relative distance between the eye and naris (4.03–4.98 versus 5.01–5.63). From P. psychonothes , we distinguish P. hylonomus by the dorsal pattern (absent/irregular flecks versus irregular dots/dots in series/dots in chevrons). From P. saonae , we distinguish P. hylonomus by the adult SVL (59.3–76.5 versus 90.9–98.3), the relative mental width (1.63–2.11 versus 1.52), the relative postmental width (2.67–2.89 versus 2.43), the relative prefrontal width (4.23–4.87 versus 4.14), the relative head width (73.8–76.4 versus 73.5), and the relative distance between the eye and naris (4.03–4.98 versus 6.43). From P. semitaeniatus sp. nov., we distinguish P. hylonomus by the SVL (59.3–76.5 versus 77.4–84.1), the relative length of digits on one hindlimb (22.8–28.2 versus 30.4–34.6), the relative forelimb length (17.1–20.7 versus 21.3– 23.8), the relative rostral height (1.72–2.28 versus 2.41–2.63), the relative head width (73.8–76.4 versus 58.8–63.8), the relative angled subocular height (0.690–1.13 versus 0.654), and the relative width of canthal iii (1.95–2.03 versus 1.80). From P. unicolor sp. nov., we distinguish P. hylonomus by the dots arranged in bars in the lateral areas (absent versus present), the midbody scale rows (33–39 versus 40), the total lamellae on one hand (34–47 versus 48), the total strigae on ten scales (169–222 versus 144), the relative length of digits on one hindlimb (22.8–28.2 versus 36.8), the relative forelimb length (17.1–20.7 versus 23.5), the relative cloacal width (7.98–8.57 versus 7.61), the relative largest supraocular width (2.65–2.90 versus 3.12), the relative longest finger length (4.47–5.27 versus 6.65), the relative head width (73.8–76.4 versus 70.8), the relative frontal width (64.0–74.5 versus 58.2), the relative distance between the eye and naris (4.03–4.98 versus 5.52), the relative width of canthal iii (1.95–2.03 versus 1.79), and the relative angled subocular width (1.61–2.75 versus 2.90).

Description of holotype. MCZ R-77160. An adult male; SVL 72.3 mm; tail nearly cylindrical, broken in life midway, regenerated, 67.0 mm (92.7% SVL); axilla-to-groin distance 40.6 mm (56.2% SVL); forelimb length 14.1 mm (19.5% SVL); hindlimb length 20.5 mm (28.4% SVL); head length 13.2 mm (18.3% SVL); head width 9.96 mm (13.8% SVL); head width 75.5% head length; diameter of orbit 2.69 mm (3.72% SVL); horizontal diameter of ear opening 1.02 mm (1.41% SVL); vertical diameter of ear opening 1.18 mm (1.63% SVL); length of all toes on one foot 19.8 mm (27.4% SVL); shortest distance between angled subocular and lip 0.41 mm (0.567% SVL); shortest distance between the ocular and auricular openings 5.59 mm (7.73% SVL); longest finger length 3.81 mm (5.27% SVL); largest supraocular width 2.00 mm (2.77% SVL); cloacal width 6.00 mm (8.30% SVL); mental width 1.35 mm (1.87% SVL); postmental width 1.96 mm (2.71% SVL); prefrontal width 3.52 mm (4.87% SVL); frontal width 74.5% frontal length; nasal height 0.99 mm (1.37% SVL); angled subocular height 0.82 mm (1.13% SVL); shortest distance between the eye and naris 3.52 mm (4.87% SVL); canthal iii width 1.45 mm (2.01% SVL); angled subocular width 1.99 mm (2.75% SVL); nasal width 1.45 mm (2.01% SVL); rostral 1.75X 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 concave posterior margin, wider than long, bordered by posterior internasals, 1 st loreals, 1 st median oculars, and the frontal; frontal much 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 above 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 –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 lower preocular (left)/upper and lower preoculars (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)/1 st median ocular, anterior supraciliary, upper preocular, and 1 st and 2 nd loreals (right); 9 (left)/10 (right) median oculars, 1 st contacting the prefrontal (left)/(right); 2 (left)/1 (right) upper preoculars; an irregular anterior supraciliary (left)/(right); 5 lateral oculars (left)/(right); 5 temporals (left)/ (right); 3 suboculars (left)/(right); posterior subocular large and elongate (left)/(right); anterior suboculars small (left)/(right); 9 supralabials (left)/(right), 6 to level below center of eye (left)/(right); 10 (left)/9 (right) infralabials, 5–7 (left)/5 (right) to level below center of eye; mental small, followed by a single, larger postmental; 4 pairs of enlarged chin shields, followed by 1 pair of reduced chin shields; 1 st pair in contact with one another; 2 nd –4 th pairs separated by 1–3 scales; 90 transverse rows of dorsal scales from interoccipital to base of tail; 97 transverse rows of ventral scales from mental to vent; 38 scales around midbody; 5 digits; finger lengths 3>4>2>5>1; 10 (right) lamellae under longest finger; 41 total lamellae on one hand; toe lengths 4>3>5>2>1; 17 (right) lamellae under longest toe; keelless and striate dorsal body and caudal scales; ventral scales smooth to faintly striated; 195 total strigae counted on ten scales.

FIGURE 61. (A–F) Panolopus hylonomus (MCZ R-77160, holotype), SVL 72.3 mm.

FIGURE 62. Panolopus hylonomus (SBH 267793), in life. From ca. 2 km S Juanillo, Altagracia Province, Dominican Republic. Photo by SBH.

Color (in alcohol): dorsal surface of head gray-tan, patternless; lateral surfaces of head grading from pale tan to cream with darker brown eye masks and other darker brown areas on the supralabial, infralabial, and throat scales; dorsal surfaces of the body are red-gray with a few paler brown flecks; dorsal surface of tail red-gray to yellow-gray (on regenerated section) with a few pale brown spots; lateral areas fading from dark gray-brown to cream with darker brown spots arranged in vertical lines; dorsal surfaces of the limbs are pale brown with darker brown mottling; lateral and ventral areas of the limbs fade to pale cream, patternless; ventral surfaces of the head, body, and tail are pale cream with some brown mottling under the throat and nearer to the sides.

Variation. No specimen has a patterned head and only AMNH 92799 shows markings in the longitudinal paramedian area (small dots in series). The lateral band is reduced in this species with no specimen showing dots arranged in bars in the lateral band before it ends. Measurements and other morphological data for the holotype and other examined material are presented in Table 1.

Distribution. Panolopus hylonomus is distributed along the extreme southeastern coast of the Dominican Republic at elevations of 0–80 m (Fig. 49).

Ecology and conservation. No ecological data are associated with this species. We consider the conservation status of Panolopus hylonomus to be Least Concern, based on IUCN Redlist criteria ( IUCN 2023). It is likely a common species tolerant of some habitat disturbance, based on what is known of most species of Panolopus . However, it faces a primary threat of habitat destruction resulting from deforestation.A secondary threat is predation from introduced mammals, including the mongoose and black rats. Studies are needed to determine the health and extent of remaining populations and better understand the threats to the survival of the species.

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

Etymology. The species name is from the Greek hylo- (forest) and nomus (wanderer), in likely allusion to the relatively isolated range of this mesic, forest-dwelling species in eastern Hispaniola ( Schwartz 1964).

Remarks. Previously considered a subspecies of Panolopus curtissi , herein we elevate P. hylonomus to the species level based on genetic and morphological differences. Additional specimens categorized as P. costatus and P. curtissi in museum collections should be examined for the diagnostic characters reported herein to potentially assign them to this species.

Panolopus hylonomus was included in our genetic dataset and has significant support in both Bayesian and ML likelihood analyses at the stem node that places it as the closest relative of P. unicolor sp. nov. Based on our timetree (Fig. 4), P. hylonomus diverged from its closest relative 0.85 Ma, consistent with typical species of vertebrates (> 0.7 Ma; Hedges et al. 2015). We also recognize P. hylonomus as a distinct species because of the multiple morphological traits that separate it from P. unicolor sp. nov., its closest relative. Panolopus hylonomus was recognized as a distinct species by our ASAP analysis.