Arthrosaura hoogmoedi

Kok, Philippe J. R., 2008, A new highland species of Arthrosaura Boulenger, 1885 (Squamata: Gymnophthalmidae) from Maringma tepui on the border of Guyana and Brazil, Zootaxa 1909, pp. 1-15 : 5-14

Arthrosaura hoogmoedi species novum

Figs. 5–6 , 7 C, 8–9

Holotype. IRSNB 2653 (field number PK 2031), an adult female collected by Philippe J. R. Kok, Paul Benjamin and Claudius Perry, 27 November 2007 at 11h00, summit plateau of Mount Maringma, Cuyuni-Mazaruni District, Guyana (5° 12’ 60” N, 60° 35’ 06” W, 2112 m elevation).

Etymology. The specific epithet is a noun in the genitive case, honoring Dutch herpetologist Marinus Steven Hoogmoed. Marinus was curator of reptiles and amphibians at the National Museum of Natural History (Leiden, The Netherlands) for 38 years (1966–2004) before retiring as research associate at the Museu Paraense Emílio Goeldi in Belém, Brazil, where he is still very active. His contribution to the knowledge of the Guiana Shield herpetofauna is extensive, and most of his papers on the lizard fauna of the area are still authoritative.

Diagnosis. The new species is assigned to the genus Arthrosaura because of the following combination of characters (modified from Ávila-Pires 1995, and MacCulloch & Lathrop 2001): (1) distinctive ear opening and moveable eyelids, (2) limbs pentadactyl with all digits clawed, (3) nasal scales separated by a single frontonasal, (4) prefrontals present (although absent in Arthrosaura synaptolepis Donnelly, McDiarmid & Myers, 1992 ), (5) frontoparietals, parietals and interparietal present, (6) parietals and interparietal longer than wide, (7) interparietal and parietals forming a straight posterior margin, (8) occipitals present, (9) second pair of enlarged genials in contact with two infralabials, (10) enlarged median pairs of gulars, (11) dorsal scales hexagonal, keeled, in transverse rows only, (12) ventral scales quadrangular, smooth, in both transverse and longitudinal rows, (13) tongue dorsally covered by scalelike papillae (although papillae are reported as interrupting oblique plicae in Arthrosaura montigena Myers & Donnelly, 2008 ).

In addition to the generic characteristics, the new species is characterized by the following features: four supraoculars; prefrontals in contact with loreals; palpebral disc completely opaque; 32–33 smooth temporal scales; scales around midbody 37; 3–4 middorsal scales distinctly narrower than adjacent dorsal scales; dorsal scales strongly keeled, in 29 transverse rows; trunk length 1.4x length of forelimb; overlap of limbs equivalent to seven lateral scales when they are adpressed along the body; dark brown dorsum with a black middorsal stripe from nape to tail, and a tan ill-defined dorsolateral line from nape to midbody; flanks black; ventrally cream with dark mottling.

The new species is immediately distinguished from Arthrosaura montigena , A. reticulata ( O’Shaughnessy, 1881) , A. synaptolepis , A. tyleri ( Burt & Burt, 1931) , and A. versteegii Lidth de Jeude, 1904 in having four supraoculars (vs. three) and a black middorsal stripe from nape to tail (absent in the above-mentioned species). The new species agrees with A. guianensis MacCulloch and Lathrop, 2001 , A. kockii (Lidth de Jeude, 1904), and A. testigensis Gorzula and Señaris, 1998 in having four supraoculars. Arthrosaura guianensis mainly differs (characters of A. hoogmoedi in parentheses) in having keeled parietals and interparietal (a feeble keel on interparietal only), unpigmented tympanum (pigmented), lower eyelid with semitransparent disc (disc opaque), 45 scales around midbody (37), 40–42 keeled temporals (32–33, smooth), and absence of a black middorsal stripe (present). Arthrosaura kockii mainly differs (characters of A. hoogmoedi in parentheses) in having broadly keeled temporals (smooth), unpigmented tympanum (pigmented), lower eyelid with semitransparent disc (disc opaque), a wide light vertebral stripe (black middorsal stripe), and in having an immaculate venter (dark mottled). Arthrosaura testigensis shares many characteristics with A. hoogmoedi , from which it mainly differs (characters of A. hoogmoedi in parentheses) in having less than 20 temporals (more than 30), lower eyelid with semitransparent disc (disc opaque), prefrontals separated from loreals by frontonasal-first supraocular contact (prefrontals in contact with loreals), weakly keeled dorsal scales (strongly keeled), middorsal scales not noticeably narrower than adjacent dorsal scales (3–4 middorsal scales distinctly narrower), and in having four narrow yellowish longitudinal stripes on dorsum (one middorsal black stripe and a tan ill-defined dorsolateral line).

Description of the Holotype. Adult female 59.3 mm SVL. Head length 21 % SVL, 1.37x head width, head width 1.48x head height. Head slightly wider than neck, temporal region swollen, neck approximately as wide as anterior body. Snout blunt, rising gently posteriad. Body oval in transverse section, depressed, wider than high. Tail complete (regenerated distally), 97.0 mm, 1.63x SVL, circular in cross-section, tapering toward the tip. Limbs well-developed, moderately long, forelimbs 31% SVL, hindlimbs 48% SVL. Limbs pentadactyl, all fingers and toes with terminal claw. Overlap of limbs equivalent to seven lateral scales when they are adpressed along the body. Trunk length 25.7 mm, 43 % SVL, 1.4x forelimbs ( Fig. 5 ).

Tongue lanceolate, dorsally covered by oblique rows of small scalelike papillae; tip bifid, smooth; three well defined pairs of subequal infralingual plicae on the anterior part of the tongue, after fork. Anterior teeth conical, posterior teeth laterally compressed, tricuspid.

Rostral rectangular, twice as wide as high, visible from above, in broad contact with frontonasal. Frontonasal single, heptagonal, laterally in contact with nasal and in broad contact with loreal, not in contact with first supraocular. Prefrontals roughly pentagonal, as broad as long, with a long medial suture, laterally in broad contact with first supraocular, touching the loreal and the anterior point of the second supraocular. Frontal hexagonal, 2.1x as long as wide, slightly wider anteriorly, laterally markedly concave; laterally in contact over the entire length of second supraocular, separated from first supraocular by prefrontal-second supraocular contact, in point contact with third supraocular. Frontoparietals roughly hexagonal, 1.5x as long as wide with relatively broad medial suture; frontoparietals in contact with frontal, distinctly separated from second supraocular by frontal-third supraocular contact, in broad contact with third and fourth supraoculars, one parietal and interparietal. Interparietal 1.6x as long as wide, roughly pentagonal with curved sides converging anteriad, distinctly longer and narrower than parietals. Parietals and interparietal form a relatively straight posterior margin; anteriorly each is angulate. Interparietal with a short median, feeble, longitudinal keel. A row of seven occipitals of various shapes, the central largest; all of them feebly keeled, except the first left one. Four supraoculars, first smallest, about half the size of the fourth; third distinctly larger, second largest. Six superciliaries, first much larger than the others, last two smallest, others subequal ( Fig. 6 ).

Nasal entire, with a very short division running ventrad from naris to supralabial on the left side; naris just below centre; directed laterally. Loreal trapezoidal, anteriorly inclined, in contact with nasal, frenocular, first superciliary, first supraocular, and prefrontal and frontonasal, separated from supralabials by frenocular-nasal contact and an odd, very small, quadrangular, supernumerary scale located at the intersection of nasal, frenocular, and first and second supralabials, present on both sides. Three small preoculars on the right side, two on the left, between first superciliary and first subocular. Frenocular quadrangular, longer than wide, subequal to loreal, separated from the first supralabial by a small supernumerary scale. Four suboculars on the right side, five on the left. Two postoculars, the lower smallest. Seven supralabials on both sides, fifth highest, with suture between third and fourth below middle of the eye; suture between second and third supralabials in contact with first subocular, suture between first and second supralabials in contact with a small supernumerary scale on both sides ( Fig. 6 ).

Upper eyelid with 10 ciliaries. Ocular recess with median row of five small scales separating median ciliaries from superciliaries. Lower eyelid with 12 ciliaries on the right side, 11 on the left side. Lower eyelid with a palpebral disc of four large, vertical, completely opaque (pigmented), palpebral scales ( Figs. 6 , 7 C).

Temporal region with 32 irregularly shaped, juxtaposed, smooth scales on the right side, 33 on the left. Temporals arranged in six ill-defined oblique rows, much larger in the upper part [a distinct cluster of 16 (on the right) and 18 (on the left) smaller temporals in the lower part]. Ear opening moderately large, vertically oval, posteriorly bordered by many small, smooth, mostly granular scales; anteriorly bordered by four (on the right side) or six (on the left side) smooth, enlarged, juxtaposed scales. Auditory meatus moderately deep, tympanum pigmented ( Fig. 6 ).

Mental trapezoidal, its posterior edge slightly concave. Postmental large, roughly heptagonal, laterally in contact with first and second infralabials. Three pairs of large genials, first two pairs in contact with each other medially, in lateral contact with infralabials, medial suture of second pair twice as long as that of first pair; third pair in contact with infralabials, but separated medially by small scales. A pair of enlarged postgenials separated medially by scales of varying sizes and widely separated from infralabials. Six infralabials on the right side, five on the left side. Six rows of two transversely enlarged gulars. Collar row with nine scales, decreasing in size laterally, forming a scalloped margin. Gular fold distinct, concealing three rows of very small scales ( Figs. 6 , 8 B).

Head scales with numerous small pits, especially concentrated on rostral, frontonasal, supraoculars and lateral head scales, absent on ventral head scales and body scales. Scales on nape posterior to the row of occipitals longer than wide, keeled, mucronate, in transverse rows, grading posteriorly into dorsal body scales. Sides of neck with distinctly smaller granular scales, juxtaposed, not in rows, slightly decreasing in size posteriorly. Three (left side) or four rows (right side) of distinctly enlarged scales before arm insertion.

Dorsals imbricate, appearing hexagonal because of imbrication, elongate, strongly keeled, mucronate, in transverse rows only, 29 rows between the interparietal and posterior edge of hindlimbs (including row of occipitals). Three to four middorsal scales, between anterior margin of forelimbs and anterior margin of hindlimbs, distinctly narrower than adjacent dorsals and very similar to laterals ( Fig. 9 A), 37 scales around midbody. A zone of small granular scales extending from anteriorly of forelimb insertion to above arm and becoming wider in the axilla. Small granular scales at hindlimb insertion. Flank scales similar to, but narrower than, most dorsal scales (except three to four middorsal ones, see above); no abrupt demarcation between dorsals and laterals. Lateral scales becoming smaller toward groin. Below the laterals, two rows of ventrolateral scales (see Myers & Donnelly 2008); some short, smaller scales intercalated between the transverse rows of laterals; no distinct demarcation between laterals and ventrolaterals.

Ventrals imbricate, smooth, longer than wide, with posterior margins slightly rounded, arranged in transverse and longitudinal rows ( Fig. 8 A). Eighteen transverse rows between collar and preanal plate, six longitudinal rows of ventrals at midbody (10 rows including the ventrolaterals). Preanal plate consisting of eight scales, three anterior scales, five posterior scales (four elongate large scales and a small distal medial triangular scale); lateral posterior preanal scales narrow, almost as long as adjacent scales. No preanal or femoral pores ( Fig. 9 B).

Scales on tail keeled, mucronate (except distally), imbricate, appearing hexagonal because of imbrication, similar to, but slightly shorter than, dorsal scales, in transverse rows only except two middorsal caudal scales that form an almost complete longitudinal row from the seventh dorsal caudal scale (from posterior margin of hindlimbs) to tip of tail. Regenerated portion of tail (distal 31.0 mm) with much shorter scales ventrally and dorsally. Pigmented subcaudal scales smooth, imbricate, with rounded ends, in both transverse and longitudinal rows, becoming keeled laterally, grading into laterals.

Dorsal surfaces of upper and lower arms with smooth, variably polygonal scales, ventral surface of upper arms with small, juxtaposed, granular scales, ventral surface of lower arms with scales similar to those on dorsal surface, except for a band on inner side with small juxtaposed granular scales. Thighs with a row of enlarged, smooth, hexagonal scales on anterior surface, bordered ventrally by two rows of slightly smaller, smooth, polygonal scales; bordered dorsally by 2–3 rows of keeled scales, diminishing in size dorsad, grading into small, granular, juxtaposed scales, which cover posterodorsal and posterior surfaces of thighs. Shanks ventrally and posteriorly with large, smooth, polygonal, imbricate scales; scales on anterior surface smaller, keeled, imbricate, grading into small, granular, juxtaposed scales, which cover distal portion of anterior side (near the ankle) and dorsal portion of shanks.

Dorsal surface of hands, feet, and digits with imbricate, smooth scales, except on the posterodorsal surface of feet where 2–3 scales are keeled; palms and soles covered with small roundish or elongate scales, juxtaposed, not projecting anteriorly. Two enlarged thenar scales on inner margin of palm below pollex, two enlarged hypothenar scales on outer margin of palm. Subdigital lamellae protuberant, slightly divided basally on some digits, single on distal halves of most digits; lamellae rounded laterally.

Subdigital lamellae as follows (Roman numbers indicate digits, Arabic numbers indicate paired or single lamellae on left/right; lower ungual sheath scale is omitted from the counts): hands I 4 /4, II 8 /8, III 14/13, IV 15/14, V 8/8; feet I 6 /6, II 9/19, III 14/14, IV 20/20, V 11/11.

Color of Holotype in life. Dorsum dark brown, with a black middorsal stripe (about two-three dorsal scales wide) extending from nape to tail, where it quickly becomes inconspicuous due to the dark coloration of the tail; subtle, irregular, tan dorsolateral line extending from nape to about midbody; flanks black, lower part of flanks peppered with reddish brown, and with some small pale brown spots ventrolaterally, forming an irregular ventrolateral line. Axilla region and underside of arms marbled with reddish brown and black. Head blackish brown with tan dorsolateral lines extending above eyes, from the anterior part of the loreals to the parietals. Tip of snout paler; diffuse paler blotches on lower part of lateral surface of head. Tympanum black, surrounded by some tan scales. Arms black, legs and tail blackish brown. Iris black ( Fig. 5 ). Tongue dark gray. Palms and soles black. Chin, throat, chest, belly, and ventral surface of upper legs cream with dark mottling; lower legs ventrally reddish brown with dark mottling; tail ventrally black, except proximally where it is dirty white peppered with black ( Fig. 8 A).

Color of Holotype in preservative. After four months in 70 % ethanol, color pattern is similar to that in life. The dorsolateral line became white and is more conspicuous, the cream coloration of the ventral surface also became white.

Distribution and ecology. The species is currently known only from the type locality, the summit of Maringma tepui in Guyana ( Fig. 1 ). The only specimen available was collected in late morning (11h00), during a sunny spell, in a large bromeliad ( Brocchinia tatei ), about 60 cm above the ground ( Fig. 10 ). Possibly the specimen was hunting for some insects and spiders that became numerous once the sun chased away the mist generally present all over the summit. One other specimen was observed on the same day (in the afternoon) in another patch of bromeliads, but that specimen escaped. Interestingly, Gorzula and Señaris (1998) and Fuentes and Rivas (2000) also reported collection of gymnophthalmids in Brocchinia tatei . This plant probably plays an important role as a refuge and food source for highland gymnophthalmids.

Discussion. Arthrosaura hoogmoedi shares many morphological characteristics with A. testigensis from Los Testigos (Estado Bolívar, Venezuela) a group of tepuis east of Auyán-tepui and situated about 180 km airline NWW from Maringma tepui. In having a black middorsal stripe, the new species resembles a putative new taxon (“ Arthrosaura species a”) reported by Gorzula and Señaris (1998: 124) from the Chimantá Massif (about 180 km airline W from Maringma tepui), unfortunately the absence of diagnostic characters and the poor quality of the photograph provided by Gorzula and Señaris (1998, photograph #89) does not allow further comparison.

Without formally naming them, MacCulloch and Lathrop (2001) postulated the existence of two species groups of Arthrosaura , one group containing the species having four supraoculars, a relatively short body with relatively long legs (which I propose to name the kockii group), the other group containing species with three supraoculars, gracile body and relatively short legs (which I propose to name the reticulata group). Among the kockii group, the presence of keeled temporals in Arthrosaura kockii (a lowland species) and A. guianensis (an upland and highland species) might indicate a close relationship between these two taxa, while the smooth temporals could indicate a close relationship between A. hoogmoedi and A. testigensis , both being highland species.

The completely opaque condition of the lower eyelid in Arthrosaura hoogmoedi is shared only with the recently described A. montigena from Auyantepui ( Myers & Donnelly 2008) and is a rare trait within the family Gymnophthalmidae . It is unknown whether this is an adaptive character to high UV radiation and intense sunshine sometimes occurring on high elevation tepuis, or whether it is a plesiomorphic character state (secondarily lost in other species). Figure 7 shows a comparison of lower eyelid condition between A. hoogmoedi and two related Arthrosaura species ( A. kockii and A. guianensis ).

Recently Myers and Donnelly (2008: 97) provided a key to the species of Arthrosaura . Unfortunately they inverted some characters of A. testigensis with those of A. guianensis and their key should be used with caution: interparietal and parietals are keeled in A. guianensis , but not in A. testigensis , and temporals are small in A. guianensis , but large in A. testigensis .

The only other lizard collected on the summit of Maringma tepui belongs to a possibly new gymnophthalmid genus, which will be treated in a separate publication.

Figures

FIGURE 1. Area map of Maringma tepui showing the type locality of Arthrosaura hoogmoedi sp. nov. (blue dot). Coordinates and boundary with Brazil are approximate and based on the available map (note that there is a substantial difference in the country boundary between this map and that shown in Google Earth). Maps elaborated after “ Roraima Sheet 40 SE ” published by the Survey Department of Guyana, 1972, and a radar image of South America by NASA / JPL / NIMA available at http: // photojournal. jpl. nasa. gov / catalog / PIA 03388.

FIGURE 5. Arthrosaura hoogmoedi sp. nov., female holotype (IRSNB 2653), 59.3 mm SVL. A: Dorsolateral view. B: Dorsal view.

FIGURE 6. Arthrosaura hoogmoedi sp. nov., female holotype (IRSNB 2653), 59.3 mm SVL. Dorsal, ventral, and lateral views of head. Scale bar is 2 mm.

FIGURE 7. Lower eyelid condition in Arthrosaura hoogmoedi sp. nov. and two related Arthrosaura species. A: Semitransparent, unpigmented in A. kockii (IRSNB 15397). B: Semi-transparent, partly pigmented in A. guianensis (IRSNB 17343). C: Completely opaque, completely pigmented in A. hoogmoedi sp. nov. (IRSNB 2653, holotype).

FIGURE 8. Arthrosaura hoogmoedi sp. nov., female holotype (IRSNB 2653), 59.3 mm SVL. A: Ventral view in life. B: Detail of the gular region in life.

FIGURE 9. Arthrosaura hoogmoedi sp. nov., preserved female holotype (IRSNB 2653), 59.3 mm SVL. A: Detail of dorsal scales at midbody showing the 3 – 4 middorsal scales noticeably narrower than contiguous dorsal scales. B: Detail of perianal region.

FIGURE 10. A patch of Brocchinia tatei (Bromeliaceae), habitat on the summit plateau of Maringma tepui in which the holotype of Arthrosaura hoogmoedi sp. nov. was found.