Arthrosaura montigena, Myers & Donnelly, 2008

Myers, C. W. & Donnelly, M. A., 2008, The Summit Herpetofauna Of Auyantepui, Venezuela: Report From The Robert G. Goelet American Museum-Terramar Expedition, Bulletin of the American Museum of Natural History 2008 (308), pp. 1-147 : 89-97

Arthrosaura montigena , new species Figures 53–57

Arthrosaura montigena (nomen nudum): Sánchez H. and Bisbal E., ‘‘2002’’ [2004]: 13 (mention of holotype in EBRG).

HOLOTYPE: EBRG 2905 (field no. CWM 19354), an adult female from summit of Auyantepui at 5 ° 589N, 62 ° 339W ( AMNH – TERRAMAR Camp 4), 1600 m elevation, Bolívar, Venezuela, collected February 22, 1994, AMNH –TERRAMAR Expedition.

PARATYPE: AMNH R-140230 ( CWM 19165), a male from summit of Auyantepui at 5 ° 519N, 62 ° 329W ( AMNH –TERRAMAR Camp 1), 1700 m, Bolívar, Venezuela, collected February 7, 1994, AMNH –TERRAMAR Expedition. Figure 53.

ETYMOLOGY: The specific name montigena is an adjective meaning ‘‘mountain born’’. It is derived from the Latin noun mons (‘‘mountain’’) + the adjective-forming suffix - genus (‘‘born or produced in a certain place’’).

DIAGNOSIS: A small highland species of Arthrosaura readily distinguished from its nearest geographic neighbor ( A. testigensis, Los Testigos range, east of Auyantepui) in having three (vs. four) supraoculars and in having a pale dorsolateral line on each side and an unmarked venter (vs. four narrow yellowish stripes on dorsum and brown spots on venter). A presumably unnamed species from the Chimantá massif (southeast of Auyantepui) evidently differs from A. montigena in having a dark brown middorsal stripe (Gorzula and Señaris, 1999: photo 89).

Arthrosaura montigena shares many characteristics of A. versteegii ( French Guiana to extreme eastern Venezuela 25) but differs in having a more complete pale dorsolateral line and in not having the ventral or ventrolateral scales sharply demarcated by a zone of small scales. A key to the named species of Arthrosaura is provided at the end of this section.

DESCRIPTION

The undissected male paratype is considered sexually mature because of its welldeveloped hemipenes with hardened spines; the undissected female holotype is significantly larger than the male and is judged to be an adult on that basis.

The following description mirrors as closely as practical that of Hoogmoed and Ávila- Pires (1992: 470–477) for Arthrosaura versteegii , with identical phrasing where appropriate (but with a few additional characters added). Possibly significant differences from A. versteegii are italicized (with the comparative data for versteegii sometimes quoted

25 As redefined by Hoogmoed and Ávila-Pires (1992: 470–477), Arthrosaura versteegii has a suspiciously broad geographic and elevational range— occurring as low as 100 m above sea level in Suriname and as high as 1400 m in Venezuela, without intervening records from Guyana. With this in mind, the two Venezuelan specimens reported by Hoogmoed and Ávila-Pires eventually need direct comparison with A. montigena , and, particularly, with Guyanese highland specimens when such become available.

TABLE 7 Measurements (in mm) and Other Data for Arthrosaura montigena , new species

within parentheses). Some characteristics of the type specimens of Arthrosaura montigena are summarized in table 7.

A small microteiid; one adult male 40 mm SVL, one adult female 48 mm SVL. Head length/ SVL 5 0.18–0.19 ; head length/head width 5 1.33–1.45; head width/head depth 5 1.20–1.45. Temporal region in male not swollen (‘‘in males distinctly swollen’’). Snout blunt, rising gently posteriad. Neck approximately as wide as head and anterior body. Body depressed, noticeably wider than high ; midbody width/height 5 1.29 8, 1.37 ♀. Tail / SVL 5 1.71 in female (incomplete in male) ; tail approximately as high as wide at base, tapering to tip. Limbs well developed, relatively short, forelimb/ SVL 5 0.25–0.27, hind limb/ SVL 5 0.40–0.44. Distance between forelimbs and hind limbs (trunk length)/forelimb length 5 1.8–2.1 (‘‘2.3– 2.6’’) .

Tongue of holotype lanceolate, anterior half gray. A central area of scalelike papillae behind fork interrupting half a dozen oblique, anteriorly aligned plicae, which extend around onto ventrolateral side of tongue as distinct folds; several partial plicae also indicated anterolaterally on base of fork. Posterior few plicae subdivided into smaller segments, with only the posteriormost line medially convergent behind the anterior scalelike plicae; remainder of visible tongue covered completely with scalelike papillae (base of tongue not accessible without undue damage to specimen). Raised midventral side of tongue with a median groove extending anteriorly through three pairs of thin (nonswollen), oblique, anteriorly converging (chevronlike) infralingual plicae immediately behind fork; first pair of infralingual papillae largest, third smallest. Anterior maxillary and dentary teeth short, becoming bicuspid and then primarily tricuspid posteriorly.

Rostral rectangular, 2.4–2.6 times as wide as high, visible from above, in broad contact with frontonasal. Frontonasal single, weakly pentagonal with small posterior apex, laterally in contact with nasal and in broad contact with loreal and also in contact with anterior point of first supraocular. Prefrontals relatively small, quadrangular (‘‘irregularly pentagonal’’), with a very short medial suture (‘‘short to relatively long’’), laterally in contact only with first supraocular. Frontal hexagonal, 1.6–1.7 times longer than wide, about as wide anteriorly as posteriorly, laterally weakly or markedly concave; frontal with a relatively broad border (‘‘usually a short border’’) with first supraocular, in contact nearly with entire length of second supraocular, and frontal either narrowly separated from third supraocular, or, on right side in male, with point contact. Frontoparietals pentagonal, little longer than wide, with relatively broad medial suture; each frontoparietal in contact with frontal, in point contact with second supraocular except on right side in male, and in broad contact with third supraocular, one parietal, and interparietal. Interparietal 1.6–1.7 times longer than wide, pentagonal with straight sides slightly converging posteriad, as long or slightly shorter than parietals, as wide as greatest width of parietals (‘‘distinctly narrower than the parietals’’). Parietals and interparietal form a relatively straight posterior margin, anteriorly each is obtusely angulate. Occipitals—the scales posteriorly touching interparietal and parietals—forming a row of five variably shaped scales in female, but reduced by fusion to three wide scales in male. Three supraoculars, first smallest, second and third subequal. Four superciliaries, first much larger than the others, median two shorter than fourth.

Nasal semidivided (‘‘undivided’’), the division running posterodorsally from naris in male and on left side of female (fig. 54), but running ventrad from naris to supralabial on right side of female; naris in center or slightly below center of nasal plate, directed slightly posterolaterally. Loreal an anteriorly inclined rectangle or, on left side of female, an irregular pentagon (fig. 54), in contact with nasal and frenocular, in narrow contact with or narrowly separated from a small preocular, and in contact with first superciliary, first supraocular, and the frontonasal; loreal dorsally excluded from prefrontal by frontonasal-supraocular contact, ventrally well separated from supralabials by frenocular. Two preocular scales, very small, between first superciliary and first subocular. Frenocular longer than wide, weakly pentagonal, about as large as loreal, followed by 3–5 suboculars (4/ 4 in male, 5/ 3 in female). Three postoculars of varying size, lowermost continuing from the subocular series, uppermost in anterior contact with last superciliary. Supralabials usually six, with either the fourth plate or the suture between third and fourth below middle of eye; suture between second and third supralabials situated either under posterior edge of frenocular or slightly posteriad; nine supralabials on right side of female owing to divisions in first and fifth plates.

Upper eyelid with eight or nine ciliaries, none exceptionally enlarged. Ocular recess with a short median row of 2–3 scales separating median ciliaries from superciliaries. Lower eyelid with 8–10 ciliaries, subequal or with one elongated. Lower eyelid scaled, with a large opaque window (palpebral disc) of three or, on left side of female, four vertical panes. Palpebral disc separated from lower eyelid ciliaries by a single row of small scales; several rows of smaller scales ventral to disc.

Temporal region between postoculars and ear with approximately 17–20 relatively large, irregularly shaped, juxtaposed smooth scales; one large anterior plate situated behind upper postocular and below suture between third supraocular and parietal; temporals otherwise increasing in size posteriorly, with two markedly enlarged scales bordering upper part of ear. Ear opening vertically oval, edged with small, smooth, somewhat swollen scales. Auditory meatus shallow, tympanum clear, not pigmented.

Posterior edge of mental nearly straight or slightly undulating. Postmental large, slightly pentagonal, laterally in contact either with first infralabial only or also with anterior end of second infralabial. Three large pairs of genials, in lateral contact with infralabials; a fourth pair of smaller ‘‘genials’’ or pregulars (fide Donnelly et al., 1992: fn. 2) separated from supralabials by 2–3 scales. First two pairs of genials in broad medial contact, with medial suture of second pair being much longer than that of first pair. Third pair of genials and pair of large pregulars medially separated by a wedge of smaller pregulars, of which 1–2 scales separate the third pair of genials and 2–4 scales separate the fourth pair of ‘‘genials’’ (or large pregulars). Only a hint of an incomplete gular crease, marked by line of granular scales from below each ear to about posterolateral edges of fourth pair of ‘‘genials’’. Gulars imbricate, smooth, with straight to rounded margins, in six transverse rows between posterior margins of last pair of ‘‘genials’’ and collar scales; first few gular rows somewhat irregular in the female; each succeeding row comprised of larger scales than the preceding, except scales in last (sixth) row smaller than in fourth and fifth rows; two middle scales in rows 4–5 forming double row of enlarged paramedian gulars. Guttural fold indistinct (‘‘gular fold distinct’’), indicated by small scales in weak fold on side of neck, ending ventrad at posterior end of fifth transverse gular row. Collar row with 7–8 scales, forming a lobed posterior margin; median four scales largest, scales decreasing in size laterad; incomplete collar fold indicated only on sides of neck behind collar, not crossing throat.

Head scales with numerous minute scale organs (pits), especially concentrated on anterior dorsal, lateral, and ventral head scales, becoming mainly distributed on margins of frontal and posterior head plates, and on posterolateral edges of body scales.

Scales on nape posterior to the row of postparietals (occipitals, see above) longer than wide, imbricate, in transverse rows, anteriorly smooth, the posterior ends round- ed to bluntly pointed; grading posteriorly into dorsal body scales. Sides of neck with distinctly smaller, mostly oval, juxtaposed scales, not in well-defined rows, becoming granular near limb insertion. Dorsals hexag- onal, elongate, strongly keeled, mucronate, in 31 transverse rows (including row of occipitals) between interparietal and posteri- or level of hind limbs. A zone of granular scales from anterior side of forelimb insertion extending above arm and becoming wider in axilla, followed posteriorly by a few vertical rows of small scales intercalated between the transverse rows of laterals; lateral scales becoming small toward groin, grading into granular scales just in front of hind limb insertion. Otherwise, the transverse scale rows are essentially uninterrupted on middle 70 % of trunk; the upper lateral scales in these rows are similar to dorsals, with lower lateral scales becoming wider, less strongly keeled, and nonmucronate; keels lost on lowermost row of laterals. Lateral scales slanted posterodorsally, tending to be aligned more posteriorly in lowermost few rows.

Below the laterals, two rows of ventrolateral scales 26 (‘‘ventrals’’), which are aligned either posteriorly or slanted posteroventrally—in a more or less abrupt change of alignment from the lateral body scales (fig. 55). Ventrolaterals (‘‘ventrals’’) not or but indistinctly demarcated from laterals by an interrupted row of widely spaced small scales (‘‘ventrals and laterals sharply demarcated by a zone of small scales’’). At most, in the space of 10 transverse rows along midsection of body, the female has an interrupted line of about half a dozen small scales inserted between lowermost lateral and upper ventrolateral rows; these inconspicuous scales are short and therefore widely spaced from one another, giving the impression of being remnants of a lost scale row (fig. 55). The equivalent midsection of the male has only a single, similarly placed small scale on each side.

Ventrals imbricate, longer than wide, with rear margins progressively becoming more

26 These ‘‘ventrolateral scales’’ are usually counted in Arthrosaura spp. as longitudinal rows of ventrals that do not form continuous rows between the pectoral area and preanal plate. But it is difficult to make ventrals of them in A. montigena because of the shape change and especially because they face laterally (with only a slight ventral inclination). The situation is possibly paralleled in young A. kockii , a species with normally 10 longitudinal ventral rows except ‘‘in the smallest specimens only the medial six rows are distinguished as ventrals’’ (Ávila-Pires, 1995: 332).

rounded posteriorly, aligned in both transverse and longitudinal rows. Both specimens with 18 transverse rows between collar and preanal. Both specimens have six continuous longitudinal rows, with outermost row on each side separated by only 1–2 scales from collar scales. Hence, six distinct ventrals in a transverse row at midbody (‘‘ten ventrals’’), or 10 ventrals if ventrolateral scales are included in this count. Scales around midbody 35 in both specimens. Preanal plate consisting of four scales, including two large laterals, and two medial triangular scales in point contact, the anterior being larger than the posterior. Male with two preanal pores in same line as four femoral pores on each side, the pores separated by 1–2 scales.

Scales on tail in transverse rows dorsally and laterally, hexagonal and otherwise similar to body scales but shorter. Unpigmented subcaudals smooth, with rounded ends, in both transverse and longitudinal rows; transverse rows forming whorls with dorsals; six longitudinal rows basally.

Dorsal surfaces of upper and lower arms, and ventral side of lower arm with large, imbricate, variably polygonal scales, mostly smooth (a few weakly keeled on male), becoming much smaller on inner side of lower arm; ventral surface of upper arm with small, rounded or somewhat swollen, imbricate, smooth scales. Thigh with 1–2 rows of large smooth scales on anterior face, bordered ventrally by 1–2 rows of somewhat smaller smooth scales reaching the line of femoral pores or equivalent area in females; large anterior scales bordered dorsally by a row of small smooth to keeled scales, grading into juxtaposed small scales and granules on posterodorsal and posterior side of thigh. Lower leg with small smooth to slightly keeled imbricate scales, becoming smaller and juxtaposed posteriorly; ventral side of lower leg with large smooth scales.

Tops of hands, feet, and digits with smooth imbricate scales; palms and soles covered with small, mostly elongate juxtaposed scales that are not thickened or raised. Two enlarged thenar scales on inner margin of palm below pollex, each with a black, produced inner edge. Similar black oblique keels present on basal sides of toes III and IV, each with several keels; each keel situated on the inner of a pair of basal subdigital lamellae. Subdigital lamellae divided basally, single on distal halves of some digits.

Subdigital lamellae as follow (Roman numbers indicate digits, Arabic numbers indicate paired or single lamellae on left/right feet); separate counts given first for male paratype, second for female holotype: forefoot I 4/4, 3/3 II 6 /6, 6/7 III 9 /9, 10/10 IV 11 / 11, 11/12 V 6 /6, 7/6 ; hind foot I 3/3, 4/4 II 7 /7, 7/7 III 12 /11, 11/12 IV 15 /15, -/15 V 11 /10, 10/ 11. (A few counts are approximations owing to variation in scales at bases of digits; the divided lower ungual sheath scale is omitted from the counts.)

COLORATION: In life (fig. 53), dorsum brown with variably distinct tan dorsolateral lines; flanks blackish brown, with some small pale spots. Palms and soles black; other ventral surfaces either sexually dimorphic or individually variable as follows: Male—all ventral surfaces except palms and soles uniformly bright orange. Female—underside of head creamy white, turning light yellow under throat and over venter and base of tail, becoming orange under distal three fourths of tail. Iris orange. Tongue black.

COLOR AND PATTERN IN PRESERVATIVE: More detailed examination of the preserved specimens (fig. 56) shows the female to have a distinct pale dorsolateral line extending from the postorbitals onto the base of the tail. The male has this line extending weakly from the eye and along the outer edge of the parietal, then becoming distinct on the neck, present but poorly defined on the body, and then again distinct from above the groin onto the base of the tail; the dorsolateral line is continued posteriorly from the proximal part of the tail as a series of pale brown spots that disappear before the end of the tail in the female (tail incomplete in male). A parallel row of white spots on lower side of tail, also disappearing before the end of tail.

The hexagonal body scales—inconspicuously speckled with brown on a lighter brown ground and with a slight darkening along the keels—are sharply bicolored, with the free ends grayish brown. The grayish distal ends overlap irregular dark brown pigmentation across the bases of the scales in each succeeding row, forming a series of dark transverse lines across the dorsum and flanks, but there is an increase in the amount of dark brown pigmentation on the flanks of both specimens, and some of the scale tips of the lateral scales are white in the male, accounting for its pale-spotted blackish sides in life (fig. 53). The pattern of dark transverse lines extends only onto base of the tail, which becomes marked with small irregular dark spots and darker keels.

Top and sides of head brown, with some slightly darker brown pigmentation but no definite patterning. Supralabials appear either brown with white spots in the male, or white with brown bars in the female. Several elongated whitish spots with darker borders on side of neck. Ventral surfaces and ventrolateral scales on lower flanks white, with some light to dark brown pigmentation on the ventrolaterals and lateral row of ventrals; no pigment on genials, but some irregular dark brown markings at base of forelimb insertion and an occasional very small dark mark in preanal area or elsewhere; ventral surfaces otherwise immaculate.

HEMIPENIS

METHOD: The genitalia of the paratype of Arthrosaura montigena were everted in the field, and the left organ was later removed and inflated with carmine-dyed petroleum jelly. Because of a puzzling, well-defined aperture between the lobes of the organ and because the apices of the lobes seemed not to fully evert, the jelly was squeezed out and the organ soaked overnight in a solution of 3 % KOH (also injected into the lumen) before being reinflated. The right organ was then removed, injected with 3 % KOH and soaked in the KOH solution for about 10 hours before being inflated. Results were comparable, however, and the two organs are essentially identical. The tips of the lobes could not be completely extended manually, even by internal probing with the round head of a no. 000 insect pin. The following description and illustrations are of the left organ, showing maximally attained inflation.

DESCRIPTION: The inflated hemipenis (fig. 57) is 5.5 mm wide by about 7 mm in overall length; it is bilobed for about 30 % of total length. The broad middle part of the sulcate side of the organ is nude, with the sulcus spermaticus being a deep, well-defined groove running a medial course to the crotch; the sulcus bifurcates as it enters the crotch, with the branches extending centripetally probably to the apices of the lobes. There is a well defined aperture (the ‘‘orificium’’) about 0.2 mm wide between the sulcate branches in the middle of the nude crotch, opening into a tunnel extending proximally into the hemipenis to a depth of perhaps 1 mm (which would 5 14 % of hemipenial length).

The median part of the asulcate side of the organ is nude from the base to the crotch. Plicae arise on either side of the nude midline in a weak chevron pattern; the basal six rows of plicae terminate laterally on each side, at a nude area on the lower side of the hemipenis; a small spine rises at the lateral terminus of rows 2–5. Starting with row 7, the asulcate plicae meet a matching set of plicae on the sides of the lobes. At magnifications exceeding 20 times, the edges of all the plicae are lined with minute, presumably mineralized spinules.

COMMENTS: The puzzling orifice (here termed orificium) in the hemipenial crotch opens into a relatively deep tunnel of unknown function. The possibility was considered that the orificium might open into the lumen of a long, uneverted process. However, the opening and the shaft are equally well defined in both left and right hemipenes and there is no visible indication that the structure might be eversible. Although the apical tips of the lobes resisted complete eversion, the hemipenes overall were maximally inflat- ed without apparent deformation of their distal, proximally extending tunnels. The orificium is a heretofore unknown hemipenial structure.

The hemipenis of Arthrosaura montigena is somewhat similar to that of Arthrosaura synaptolepis (fig. 3 in Donnelly et al., 1992), which differs most notably in having the hemipenial lobes terminally flattened and in having a bumplike ‘‘pronounced elevation of tissue’’ instead of an orificium. Clearly, there is considerable taxonomic potential in the hemipenial morphology of Arthrosaura .

REMARKS

The male paratype of Arthrosaura montigena was found active during the morning, on the forest floor (fig. 4 bottom) near Camp 1. The female holotype was under a rock near a forest stream at Camp 4.

Small brown lizards are hard to see and harder to catch in dense montane vegetation, and upland species of Arthrosaura are therefore poorly represented in collections. Seldom is more than a specimen or two taken at a given locality. Distributions at least have the appearance of being generally limited, and additional species must be waiting discovery in the Guayana highlands.

The key below is a practical guide to the currently recognized taxa of Arthrosaura , updating the species revised by Hoogmoed and Ávila-Pires (1992) with subsequent additions by Donnelly et al. (1992), Gorzula and Señaris (1999: 117–124), MacCulloch and Lathrop (2001), and the present paper. We have not seen specimens of A. versteegii , A. testigensis , or A. guianensis , but have relied for data on the descriptions in Hoogmoed and Ávila-Pires (1992), Gorzula and Señaris (1999), and MacCulloch and Lathrop (2001), respectively.

Asterisks (*) in the key mark the four species named from Venezuelan tepuis. Additional to these, an unnamed species on the Chimantá massif may be distinguishable by the combination of a broad dark brown middorsal stripe and pale dorsolateral lines (see Gorzula and Señaris, 1999: photo 89—anterior half of body in dorsal view). Another probably unnamed species of Arthrosaura , from Cerro Yaví in the northwestern tepuis, is known only from a tail that had been ingested by a snake (Myers and Donnelly, 1996: 22, fig. 15).