Adercosaurus vixadnexus, MYERS & DONNELLY, 2001

MYERS, CHARLES W. & DONNELLY, MAUREEN A., 2001, Herpetofauna Of The Yutajé - Corocoro Massif, Venezuela: Second Report From The Robert G. Goelet American Museum-Terramar Expedition To The Northwestern Tepuis, Bulletin of the American Museum of Natural History 2001 (261), pp. 1-1 : 1-

Adercosaurus vixadnexus , new species Figures 31–36 , 37 (top), 38, 39

HOLOTYPE: EBRG 3126 (field no. CWM 19809), an adult male from wet gallery forest on Cerro Yutaje´ , 1700 m (5°46̍N, 66°08̍W), Amazonas, Venezuela; collected February 25, 1995, AMNH –TERRAMAR Expedition. See locality 1 on map (fig. 1).

ETYMOLOGY: The species name is compounded from the Latin adverb vix (barely, hardly) + the passive past participle adnexus (tied together or joined, connected), calling

22 Both Boulenger (1900) and Uzzell (1973: 54) stated that the holotype of Prionodactylus leucostictus —type species of Riolama Uzzell —has all digits clawed. But E. N. Arnold kindly examined the specimen at our request and assured us that the first finger is clawless, as in a specimen of Riolama from Cerro Duida (Myers and Donnelly, 1996: 22n). D. M. Harris (personal commun.) and R. W. McDiarmid (personal commun.), who have studied the holotype and other specimens, consider a clawless first finger to be diagnostic of Riolama .

attention to the possibly diagnostic point contact of the frontoparietal plates (fig. 34).

DIAGNOSIS: The generic definition and diagnosis are thought to differentiate Adercosaurus vixadnexus from all other teiids. The point contact of the frontoparietals, if a consistent character, will alone separate A. vixadnexus from other teiids with few exceptions (see Remarks).

On the Guayanan tepuis, A. vixadnexus is most likely to be confused with the upland species of Arthrosaura , which have brown dorsa, similar body scalation, and sometimes dark ventral markings; also the third pair of genials are in lateral contact with the infralabials in both genera. However, as indicated above, Arthrosaura is immediately distinguished from other tepui microteiids in having the posterior margins of the parietals and interparietal forming a nearly straight line across the rear of the head, and Adercosaurus further differs significantly from Arthrosaura in tongue morphology and in having a linear series of curved, nude tissue ridges across the asulcate side of the hemipenis (rather than oblique folds with comblike rows of mineralized spinules).

The general appearance of the black­outlined, white­centered ventral markings of the holotype of Adercosaurus vixadnexus , including the mottled throat (figs. 31, 32, 35), probably is distinctive among teiids generally and is quite different from the several tepui lizards with dark ventral surfaces. Arthrosaura tyleri tends to have dark­centered ventral scales and lacks the throat mottling (Donnelly et al., 1992: fig. 4). Male Prionodactylus goeleti may have extensive black on the throat and venter (Myers and Donnelly, 1996: fig. 18), and the male holotype of P. nigroventris was ‘‘shiny jet black’’ over all ventral surfaces (Gorzula and Señaris, 1999: 137), but these Prionodactylus differ noticeably from Adercosaurus in having small lateral scales and a vivid pale labial line extending posteriorly to the shoulder. The tepui endemic Riolama leucosticta differs in being overall black with small, vividly defined yellow spots and yellow mandibular stripes (Gorzula and Señaris, 1999: color photo 91), and Riolama (including unnamed species) also is immediately distinguished from Adercosaurus by lacking a claw on the first finger.

DESCRIPTION OF HOLOTYPE

The undissected male holotype is the only known specimen. It is adult judged by the well­developed hemipenes. Snout–vent length 55 mm; tail length 79 mm (regenerated); head length (obliquely from tip of snout to edge of ear) 10.6 mm; greatest head width 7.7 mm; greatest head depth 5.5 mm; snout–axilla length 20.5 mm; length of neck (posterior edge of ear to forearm) 8 mm; trunk length (axilla–groin) 28 mm; length of forelimb and of hindlimb (from axilla or groin to tip of longest digit) 11 and 15 mm, respectively.

Head length 19% of SVL, 1.4 times longer than wide, and 1.4 times wider than high; head wider than neck. Neck long, 75% of head length, 29% of trunk length. Snout–axilla length 73% of trunk length, 37% of SVL. Body wider than deep. Tail externally appears to be original, but a radiograph (fig. 32) shows that distal third is regenerated (i.e., caudal vertebrae replaced by cartilaginous rod); regenerated tail 1.5 times SVL; tail nearly cylindrical, with barely perceptible lateral compression and slight ventral flattening. Limbs pentadactyl, all digits clawed (fourth digit lost from left hand). Forelimbs 21% of SVL, 39% of trunk length; hind legs 28% of SVL, 54% of trunk; adpressed limbs not overlapping, widely separated by five or six lateral scales.

Tongue (fig. 33) lanceolate, anterior half gray. Most of anterior half behind fork with oblique, anteriorly converging plicae, which extend around onto ventrolateral sides of tongue as distinct folds. Posteriorly, these elongate plicae start to become subdivided into shorter sections before they are replaced by a zone of scalelike papillae, which occupy the midsection of the tongue in an area overlapping the pigmented anterior and unpigmented posterior halves. Behind the scalelike papillae, the mostly unpigmented posterior half of the tongue again bears distinct, anteriorly converging plicae in the shape of chevrons; the proximal half dozen or so of the posterior plicae are emphasized by gray pigmentation along their free edges. Raised midventral side of tongue with a median groove, which continues anteriorly through three pairs of thin (nonswollen), oblique, anteriorly converging (chevronlike) infralingual plicae immediately behind fork; first pair of infralingual plicae slightly larger than second pair, third pair barely indicated. 23

Anterior maxillary and dentary teeth nearly conical, slightly recurved; posterior maxillary and dentary teeth primarily bicuspid, with a rare tricuspid tooth; small pterygoid teeth present. 24 Phalangeal formula of hands 2­3­4­5­3, of feet 2­3­4­5­4.

23 The appearance of the infralingual plicae is similar to the condition illustrated for Ptychoglossus by Harris (1985: 562, fig. 2b), except that the apices of the anteriorly converging plicae are pointed in Adercosaurus , not slightly rounded.

24 Tiny teeth on the pterygoid could be seen under magnification after the lower jaw was widely reflected (for the purpose of photographing the tongue). However, the pterygoid teeth are not discernible by magnification of a radiograph of this specimen, which lends support to Harris’ (1994: 230) suggestion that pterygoid teeth in some small teiids have been overlooked by investigators who relied on radiographs.

Head scales (fig. 34) smooth, with numerous minute scale organs (pits) especially concentrated on anterior head plates (dorsal, lateral, and ventral), becoming posteriorly situated mainly on margins of head plates and nape scales. Similar minute pits also sparsely distributed on edges of dorsal scales.

Snout rounded. Rostral plate much wider than deep, laterally in contact with nasal and first supralabial, dorsally in contact with frontonasal. Anterior and posterior edges of frontonasal nearly straight. Paired prefrontals medially in broad contact. Frontal slightly hexagonal, with weak anterior apex and pronounced posterior one, longer than wide. Frontoparietals two, rhomboidal, barely in median contact. Supraoculars four, in contact with superciliary series; posterior two supraoculars on right aberrantly subdivided (fig. 34). Interparietal longer than wide, heptagonal, with anterior apex and short, straight posterior edge; lateral edges of interparietal not quite parallel, slightly diverging posteriorly. Parietals longer than wide, but shorter than interparietal, which extends farther cau­ dad—posterior margins of parietals and interparietals forming a jagged line across rear of head. Occipitals (postparietals) three, followed by a medially interrupted transverse row of four smaller postoccipitals, which in size are subequal with dorsal neck scales.

Nostril situated below center of nasal, which is undivided albeit with a very faint, thin groove below nostril. Loreal anteriorly inclined, higher than wide, dorsally in contact with frontonasal and first supraocular at their narrow suture, ventrally well separated from supralabials by frenocular. Preocular scales two, very small, between first superciliary and first subocular. Superciliaries five, with an azygous scale on both sides lying above the suture between small second and third superciliaries, and below suture between second and third supraoculars; first superciliary long and wide. Suboculars four, moderately large, behind frenocular, none greatly elongate. Postoculars two, upper smallest, between superciliary and subocular series. Supralabials seven on left side, six on right, ultimate plate smallest on each side.

Upper eyelid with eight or nine ciliaries, none exceptionally enlarged. Ocular recess with one row of small, flat scales separating all but first few and last few ciliaries from superciliaries. Lower eyelid with nine ciliaries of subequal size. Lower eyelid scaled, with a large but not well­defined opaque median window (palpebral disc) with approximately six vertical divisions. Palpebral disc mostly in contact with lower eyelid ciliaries, with only a few minute scales intervening.

Temporal region between postoculars and ear with approximately 21 irregularly shaped, juxtaposed smooth scales. Ear opening vertically oval, edged around with small, smooth scales, those on anterior edge swollen; a row of small flat scales around inner rim of opening. Auditory meatus shallow, tympanum lightly pigmented.

Posterior margin of mental nearly straight. Postmental large, slightly pentagonal, wider than long, laterally in contact only with elongated first infralabial on each side. Genials in three pairs, all in contact with infralabials; first two pairs in broad median contact; third pair of genials widely separated by intervening pregular and other scales. A pair of sideby­side, moderate­size postgenials (or pre­ gulars) in posterior contact with each member of the third pair of genials; lateral member of each pair of postgenials separated from infralabials by an elongated sublabial. The third pair of genials and the two pairs of postgenials widely separated by wedge of three pairs of pregulars, first pair in contact, second and third pairs separated by irregular smaller scales.

A narrow but distinct gular crease crossing anterior edge of throat from ear to ear, evident in both lateral and ventral view; gular crease bearing a line of tiny scales contiguous laterally but becoming widely separated ventrally. Seven transverse rows of gulars between gular crease and collar scales; first several gular rows somewhat irregular (third row incomplete); two middle scales in last three rows forming double row of enlarged, paramedian gulars, each succeeding pair larger than the preceding (fig. 35). Gulars im­ bricate. Well­defined guttural fold, with tiny scales, not crossing throat, ending ventrolaterally on each side at suture between second and third double rows of enlarged gulars. Collar row with seven scales, the median scale about as wide as long and much larger than the longer­than­wide lateral collar scales. Collar fold very evident, with 2–3 rows of tiny scales broken by median gap. Conspicuousness of anterior gular crease, incomplete guttural fold, and collar fold not due to distention of neck with preservative— all evident in life (as determined by enlargement of transparency used for fig. 31, bottom).

Sides of neck with covering of mediumsized, oval or rounded, smooth juxtaposed scales, arranged in about eight oblique rows, which do not (or only weakly) form annuli with nape and gular scales. Last two rows of neck scales anteriorly delimited by 1–2 rows of tiny scales in guttural fold and posteriorly delimited by tiny scales anterior to arm. Area of roughly 6–8 rows of tiny scales in axilla continuing as semicircle up over arm and then ventrad, with a few rows then confluent with tiny scales in collar fold.

Dorsal and lateral scales (fig. 36) elongat­ ed, parallel­sided, hexagonal, 25 keeled and strongly mucronate—keels extending posteriorly as elongated, acute points. Scale keels sharpest dorsally, becoming sharpest posteriorly on body, losing definition on nape and sides of body, where narrow median keels are replaced by wider, smooth­top elevated thickenings. Dorsals and laterals otherwise homogeneous, in uninterrupted transverse rows; no lateral fold or line of small scales. Dorsals in 36 transverse rows between inter­

25 Although misleading, ‘‘hexagonal’’ is a venerable and still useful descriptor for the body scales of some microteiids. Hexagonal scales are parallel­sided, elongated pentagonal scales that are arranged in transverse but not in longitudinal rows. The free pointed tips of laterally adjacent scales fall into sutures between scales in the next transverse row, causing each single scale to appear six­sided.

parietal and posterior edge of thigh held at right angle to body.

Caudal scales (fig. 37, top) similar to body scales, in uninterrupted annuli (no intervening small scales); supracaudals not forming paramedian series along a vertebral suture; supracaudals strongly keeled to end of tail, keels becoming broader and blunter on lateral scales and disappearing ventrally.

Ventral scales forming both transverse and weak longitudinal rows. Ventrals in 21 transverse rows between collar and pair of anterior preanals, with some irregularity in size of scales in first and last rows. Ventrals in about eight longitudinal rows of smooth scales at midbody—a subjective count inasmuch as the mucronate lateral scales grade imperceptibly into ventrals, both in shape and in a gradual shift to longitudinal rows; lateralmost one or two scales bluntly pointed; scales in median four or five ventral rows nearly rectangular, but with their free edges slightly rounded and barely overlapping the bases of scales following (i.e., weakly imbricate).

Marginal preanal scales three, outer two more than twice the size of median one; pair of elongate preanal scales in posterior contact with the small, median marginal scale (fig. 35). Femoral pores 2/2 on posteroventral surface of thigh, preanal pores 2/ 2 in same line as femoral pores; each femoral and preanal pore surrounded by 3–5 irregularly shaped small scales.

Scales on dorsal surface of arm, hand, and ventral side of forearm large (wider than dorsal body scales), imbricate to juxtaposed, smooth, rhomboidal or irregularly shaped; scales on underside of upper arm small, smooth, slightly swollen, juxtaposed. Scales on anteroventral surface of thigh and most of lower leg large, mostly smooth (a few keels on posterior scales atop thigh); posterodorsal and posterior surface of thigh pebbled with smooth, swollen granules. Supradigital scales glossy, squarish or longer than wide, distal scale proximal to ungual scale especially elongated. Palms and soles covered with small, rounded juxtaposed scales that are not thickened or rounded. Two enlarged thenar scales on inner margin of palm below pollex (fig. 38), each with produced inner edge; a similar but smaller pair of enlarged keeled scales below first toe. Subdigital lamellae divided (each half tends to be inclined up toward the middle, forming median subdigital keel between the paired scales, but this may be an artifact of preservation or desiccation).

Subdigital lamellae as follow (Roman numerals indicate digits, Arabic numbers indicate pairs of lamellae on left/right feet): forefoot, I 4/4 II 6/6 III 8/8 IV —/9 V 6/6; hind foot, I 4/3 II 6/7 III 10/10 IV 14/14 V 8/8. (A few of these counts are approximations owing to a combination of desiccation and variation in scales at bases of digits; the divided lower ungual sheath scale is omitted from the counts.)

COLORATION: In life (fig. 31), the dorsum was brown, with indication of a paler brown dorsolateral line; the sides were black with whitish flecks; the ventral surfaces were strikingly patterned in black and white.

Close inspection of the preserved specimen (fig. 32) shows the brown dorsal scales to be finely mottled with darker brown. The paler tan dorsolateral line extends posteriorly from the eye, across the upper temporal region, and well above the ear to the anterior body. The dorsolateral line reappears at the end of the body, extending above the hind legs and onto the base of the tail for a distance of 7–8 caudal annuli. The sides of the body are mostly black, with irregular small whitish and tan spots. The lips are dark except for a few small white areas, which are situated mainly along the edges of the mouth at sutures between the labial scales. The underside of the head is mottled black and white, turning darker on the throat. The basal and lateral edges of the ventral and most subcaudal scales are black, offsetting grayish white centers.

HEMIPENIS: The genitalia of the holotype were field everted, and the left organ was subsequently removed and inflated with red petroleum jelly (fig. 39). This hemipenis is 5 mm long, with a greatest width of nearly 4 mm. The organ is bilobed, each of the short symmetrical divisions terminating in a flattened, trilobed apical disc of thick tissue. The two discs tilt slightly mediad toward one another, with the medial lobe of each disc being deflected distad, resulting in paired projections between the outer flat parts of the discs.

The sulcus spermaticus is a broad, indefinite channel, from which two narrow, ill­defined groves form below the crotch (without visible bifurcation); these weak, distal sulcate branches diverge with centrolineal orientation, each branch extending into the gap between the medial and sulcate­side lobes of the apical disc. The thickened tissue comprising the apical discs is proximally continuous with the broad medial band of tissue that bears the sulcus spermaticus (fig. 39).

There is a conspicuous series of 11 or 12 curved, nude tissue ridges across the asulcate surface, encircling the side of the organ and terminating laterally on the sulcate face. The distal ridge at the base of a hemipenial lobe is small and ill­defined; the continuity of the basal seven ridges is broken on the side of the organ by a nude area extending up from the base. No mineralized spines, spinules, or hooklike papillae are evident at high mag­ nification, nor were such structures evident after the organ had been immersed for 24 hours in a solution of Alizarin Red.

REMARKS

The unique specimen of Adercosaurus vixadnexus was found near camp by our colleague Paul Sweet, at about 8 a.m. on a sunny morning, after a night of local flooding (which sometimes displaces small inhabitants of the ground litter). It was on soggy ground at the edge of wet mossy gallery forest. We assumed in the field that the specimen was an Arthrosaura , but, in preparing this paper, we found that it fits neither there nor in such extralimital genera as the physiognomically similar Ptychoglossus (see Harris, 1994). Adercosaurus thus joins Riolama (Uzzell, 1973) as a second genus of microteiids that seems to be endemic to the Venezuelan tepuis. Their relationships remain to be determined.

Our colleague Dennis Harris (personal commun.) called our attention to the possibly diagnostic point contact of the frontoparietal plates. Harris noted that the form of the frontoparietals is very conservative in ‘‘group II teiids’’, except for obvious (bilaterally assymetrical) anomalies or when there are radically different head scales (as in Neusticurus , Echinosaura, Teuchocercus ). Otherwise, the frontoparietals, unless absent (as in Gymnophthalmus ), characteristically have a broad median suture. Interestingly, one exception is Arthrosaura reticulata , in which the medial suture varies ‘‘from short to relatively wide’’ (Avila­Pires, 1995: 337, fig. 111).

A resemblance in tongue morphology between Adercosaurus and Riolama is of interest, although variation in lingual surface morphology is not well accounted for. According to Uzzell (1973: 52), the holotype of Riolama leucosticta has a tongue ornamentation of chevron­shaped plicae on the anterior and posterior thirds, separated by scalelike papillae on the middle third—similar to Adercosaurus as described herein. However, at least in some Riolama spp. (e.g., AMNH 141343, Cerro Duida, and AMNH 132118– 132119, Cerro de la Neblina) the tongue seems almost entirely plicate, with, at most, a few short, scalelike subdivisions of the pli­ cae occurring on the lateral edges of the tongue at its midsection. A Brazilian microteiid, Ecpleopus gaudichaudi , has a variable tongue morphology according to Uzzell (1969: 5), who stated that ‘‘the middle and sometimes the posterior part’’ are covered with scalelike papillae, but that the usual plicae at the anterior tip were lacking in one specimen. Another specimen of E. gaudichaudi (AMNH 131869) not then available to Uzzell clearly has anterior and posterior lingual plicae interrupted by a midsection of scalelike papillae.

Macroteiids and nearly all microteiids are characterized by scalelike papillae over most of the tongue. Often it is not convenient to examine the proximal part of the tongue without risk of damage to the specimen, but a combination of anterior scalelike papillae and posterior plicae is the common condition according to Ruibal (1952: 511), who stated that ‘‘Actually most teiids that have imbricate scale­like papillae on the tongue may have the posterior bifurcation covered with oblique plicae.’’

Heretofore, only Alopoglossus , Ecpleopus , Ptychoglossus , and Riolama seem to have been reported to have plicae also on the anterior part of the tongue (Uzzell, 1973: 54), with the fully plicate tongues of Alopoglossus and Ptychoglossus being ‘‘practically a unique feature’’ (Harris, 1994: 229). But the taxonomic distribution of anterior lingual plicae, as well as extent of intraspecific variation, is not known with certainty. This was brought home by casual examination of specimens of the long­tailed microteiid genus Pantodactylus . Specimens of Pantodactylus schreibersii (AMNH 32776, 144571) have, as expected, mostly scalelike papillae and posterior plicae, but a specimen of P. quadrilineatus (AMNH 131877, São Paulo) has anterior plicae that give way to scalelike papillae posteriorly (proximal part of tongue not examined).

Most of the morphological features commonly used to diagnose genera of Teiidae have been in use for over a century (see Boulenger, 1885: 330 et seq.). However, in a series of important papers in the 1960s and 1970s, Thomas Uzzell removed and stained the uneverted hemipenes of many microteiids (see especially Uzzell, 1973: 40–46). Uzzell showed that, in addition to various small spines, the hemipenes of many if not most microteiid genera have facing series of oblique or chevron­shaped folds or flounces that bear comblike rows of mineralized spi­ nules, which are easily stained with Alizarin Red. The complex folds formed by the lobes at the tip of the uneverted organ were not amenable to study by dissection, and the spinule­bearing flounces on the body of organ were characterized as being in pockets. With more field­inflated hemipenes becoming available, the spinule­bearing flounces are seen to be superficial on the surface of the everted organ (e.g., Donnelly et al., 1992: fig. 3; Myers and Donnelly, 1996: fig. 20), and the everted apices take on recognizable shapes of systematic value (see especially Harris, 1994).

‘‘Nude’’ hemipenes lacking mineralized spines or spinules, although uncommon among microteiids, are characteristic of Ecpleopus (Uzzell, 1969: fig. 8, uneverted) and Ptychoglossus , with the latter having ‘‘flounces of the form found in macroteiids and the closely related genus Alopoglossus , a primitive condition among microteiids’’ (Harris, 1994). Adercosaurus resembles Ptychoglossus and Alopoglossus in general hemipenial morphology. The similarity of the asulcate nude ridges or flounces can be seen by comparing photographs of the left evert­ ed hemipenes of Adercosaurus vixadnexus (fig. 39) and Ptychoglossus plicatus (Harris, 1994: fig. 17 [AMNH 114307]). Not visible in photographs are extremely minute bumps or microknobs, which are barely discernible on these two organs under the dissecting microscope; their structure is not resolvable at a magnification of Χ50. Possibly these are the ‘‘densely packed minute hook­like papillae’’ said by Harris (1994: 229, 231) to ornament the nude flounces of Ptychoglossus and Alopoglossus . If so, they are too easily overlooked to provide taxonomic content at this time. They probably represent the largest features in the epithelial landscape, which is best studied by scanning electron microscopy.

Prionodactylus goeleti (Myers and Donnelly) , new combination Figures 40 , 41 , 42 (top), 43 (part)

Euspondylus goeleti Myers and Donnelly, 1996: 23–31 , figs. 16–20. Holotype EBRG 3112 (field no. CWM 19639) from summit of Cerro Yavı´ , 2150 m, Amazonas, Venezuela; collected Feb­ ruary 19–20, 1995, AMNH–TERRAMAR Expedition.

Prionodactylus phelpsorum (Lancini) : Gorzula and Señaris, 1999: 139–141.

MATERIAL: AMNH 147038 (juv.), 147039 (egg shells), EBRG 3127 (egg shells), Cerro Yutaje´, 1700 m, February 24–28, 1995.

An additional juvenile (‘‘ MHNLS 11387’’) was reported by Gorzula and Señaris (1999: 139) as being collected first on Cerro Corocoro on November 10, 1977, and secondly in the Serranía de Yutajé on March 22, 1988 —presumably there actually are two specimens, although on page 141 they repeated the same number for ‘‘a juvenile male’’ from each locality.

REMARKS

The only lizard of this species obtained by us on Cerro Yutajé is an unsexed juvenile taken on rocks at the edge of a stream, at the 1700 m camp (fig. 40, left). A nesting site was found in a small mat (0.09 m 2) of vegetation atop bare sandstone, in Tyleria – Stegolepis – Brocchinia scrub. Hatched eggshells of different­aged clutches were found on the rock underneath the small mat of vegetation and also in cavities within the mat. Two measurable shells were 10.6 and 11.0 mm long by 6.0 and 6.8 mm wide. Communal nest sites on Cerro Yaví were under rocks, mostly on layers of fibrous plant material or occasionally on fine sand (Myers and Donnelly, 1996: 30).

Our specimen from Yutajé is a juvenile of 25 mm SVL. In life, the pale middorsal stripe was beige and the dorsolateral and lateral lines were pale brown, with the lateral line being anteriorly confluent with a white labial line. The underside of the head was whitish and the venter pale green. Iris orange. Tongue sharply bicolor, the anterior third black.

The specimen compares favorably with three juveniles in the type series of Prionodactylus goeleti , collected several days earlier on neighboring Cerro Yavı´, although a few differences can be found, especially the following: (1) the Yutajé specimen has relatively smaller scales in the midgular region (fig. 41). Although subtle, the difference could be seen with a jeweler’s loupe when the freshly preserved specimens were compared in the field. (2) The Yutajé specimen has a narrower middorsal stripe than do any of the three juveniles from Cerro Yavı´. The last specimens are pictured in Myers and Donnelly (1996: fig. 19). One of the Yaví juveniles is shown here (fig. 40, right) in direct comparison with the Yutajé specimen, in which the median stripe is 1 scale wide between the arms, 1 ½ scales at midbody, and 3 scales wide above the inguinal region. Gorzula and Señaris (1999: 141) described the stripe of another juvenile from the Serranía de Yutajé as being similarly narrow (1 scale wide at nape, 2 scales at midbody, 3 scales above inguinal region). (See below for discussion of stripe width on Cerro Yavı´.)

The samples are of course too small for reliable extrapolation. Nonetheless, the narrow median stripes in the aforementioned two juveniles from Cerro Yutajé suggest that the adults may also have narrower stripes than the adult lizards on Cerro Yavı´. If so, Prionodactylus goeleti on the Yutaje´–Corocoro massif is slightly differentiated from the population at the type locality.

TAXONOMIC NOTES

GENERIC STATUS: We follow Gorzula and Señaris (1999: 140) in their reassignment of Euspondylus phelpsorum (including E. goeleti ) to Prionodactylus , although the generic situation remains unsatisfactory. Uzzell (1973) considered the type species of Euspondylus to be ‘‘essentially devoid of unusual external morphological’’ features, and he revived the younger name Prionodactylus from the synonymy of Euspondylus for species having ‘‘a double row of widened gular scales and keeled hexagonal scales’’. But these characters, even in combination, do not uniquely define Prionodactylus , and Euspondylus remains loosely defined. Paired median gulars seem to be a tendency in several microteiid lineages, and the character apparently is not strongly fixed in some Prionodactylus . Avila­Pires (1995: 453, 456, 470) not­ ed that the gulars are occasionally irregular and not arranged in pairs in P. argulus and P. oshaughnessyi .

The hexagonal dorsal scales in Prionodactylus (and some other genera) appear distinc­ tive when sharply keeled and strongly angular, but it is only a degree of difference from Euspondylus maculatus (type species), which has relatively wider (less elongate) rectangular scales. As in Priondactylus, however, the scales are disposed in transverse rows only, so that acquisition of points on the posterior scale margins would give the appearance of hexagonal scales. The presence or absence of keeling is not an absolute difference, inasmuch as some specimens of Peruvian Euspondylus maculatus have weakly keeled dorsals posteriorly on the trunk (keels absent in AMNH 1704 but present in AMNH 56268; posterior keeling was report­ ed for a syntype by W. Peters, ‘‘1862’’ [1863]: 207).

Whether all the species of Prionodactylus form a monophyletic group that excludes Euspondylus maculatus is a problem for future revisionary work. Meanwhile, the generic reallocation of Venezuelan tepui species by Gorzula and Señaris has the practical advantage of associating them in the same group with the similar­appearing Andean Prionodactylus vertebralis (fig. 42, bottom).

SPECIES RECOGNITION: Prionodactylus goeleti was described by Myers and Donnelly (1996: 23–31) on the basis of six specimens (3 adults, 3 juveniles) collected on Cerro Yaví in 1995. The species was recognized as being probably related to Prionodactylus phelpsorum (Lancini, 1968) , which was described from an adult female taken in 1967 on Cerro Sarisariñama, 26 some 240 km south­

26 The type locality of Prionodactylus phelpsorum must be corrected as pointed out by Gorzula and Señaris (1999: 140), who called attention to a locality emendation by Steyermark and Brewer­Carías (1976: 180). Phelps (1977: 16 and map 1) provided further details of the geographic confusion that occurred on his pioneering 1967 expedition, when the lizard was collected. Owing to topographic complexity and misleading information from Maquiritare Indians, Phelps established a ‘‘Campamento Cerro Jaua’’ on what actually was the western side of the mesa of Cerro Sarisariñama.

Phelps (1977: 16–17) changed his specimen data from Cerro Jaua to Cumbre Occidental, Meseta de Sarisariñama, with coordinates estimated at 4°45̍N, 64°26̍W. The helicopter­supported camp was occupied by Phelps’ party for 10 days (March 20–29, 1967), with collecting carried out between 1900 and 2050 m above sea level. The holotype of Prionodactylus phelpsorum was taken at 1917 m on March 29 (Lancini, 1968: 2).

The locality was shown by Phelps (map 1) as ‘‘Cam­

east of Cerro Yavı´. The main diagnostic difference was that goeleti ‘‘is distinguished by a posteriorly expanded middorsal stripe.’’

The three adult and three juvenile P. goeleti were separately described, with clear indication of ontogenetic change in relative width and posterior widening of the middorsal stripe: ‘‘Three juveniles are colored similar to the adults although the pale brown middorsal stripe is relatively narrower and its posterior widening is less pronounced in the juveniles than in adults’’ (Myers and Donnelly, 1996: 27). The point was made with facing­page photographs comparing all specimens in the type series of goeleti , and equivalent stripe widths (total scales covered) were given for adults and juveniles (p. 27), as summarized below:

Adults Juveniles Stripe width (scales) (scales)

Between arms 2–3 2 ½ Midbody 3 ½ –4 3–4 Inguinal region 5 4

We reiterate the above variation because we evidently should have dwelled on its obvious taxonomic implications, namely that ontogenetic variation should not be confused with noncorrelated individual variation and that the dorsal stripe in phelpsorum (juveniles unknown) is best compared with the adult condition in goeleti ; juvenile goeleti have narrower stripes (although they too show the diagnostic posterior widening). In allocating the name Euspondylus goeleti to the synonymy of Prionodactylus phelpsorum, Gorzula and Señaris apparently confused ontogenetic variation with the kind of extensive intraspecific variation that is not correlated with age, sex, or geography. This caused them to differently interpret Lancini’s photograph of the phelpsorum holotype —an adult female containing two eggs.

Lancini (1968) does not mention whether or not the middorsal stripe is expanded posteriorly. However, [Lancini’s] Figure 7 shows a[n]

pamento Phelps–Steyermark, 1967, 2000 m’’, and a photograph (fig. 2) of the habitat at 2000 m also was given. A camp on Cerro Jaua was later established, as shown on the same map. oblique view of the dorsum of the holotype where it can be seen that the middorsal stripe is narrow anteriorly [and posteriorly] and widens to cover the dorsal surface of the tail [emphasis added]. In addition, the photographs of Myers’ and Donnelly’s own specimens show variation in the width of the middorsal stripe. For example, it is narrow in AMNH 14133 [sic (presumably 141331, a juvenile)]. Of the specimens reported here, the middorsal stripe of MHNLS 11387 (juvenile male from Serranía de Yutaje´) is only 1 scale wide at the nape, 2 scales wide at midbody and 3 scales wide above the inguinal region. (Gorzula and Señaris, 1999: 140–141)

Stripe width on the tail is not relevant to the present discussion, and the Yutajé juvenile described above obviously has the stripe posteriorly widened on the body, as does our juvenile specimen from Cerro Yutajé (fig. 40, left). Lancini (1968: 3) said that the middorsal stripe of phelpsorum was up to two scales wide (hasta dos escamas de anchura), which seems consistent with his photograph showing a median stripe that is apparently narrow for the length of the trunk. An enlarged copy of Lancini’s photograph of Prionodactylus phelpsorum is reproduced in figure 43, in side­by­side comparison with the adult type specimens of Prionodactylus goeleti . The phelpsorum holotype is obviously more robust than the specimens of P. goeleti , but that may be due to a combination of gravidness and distention with preserving fluid. In any case, despite the oblique view, it seems clear that Lancini’s description of the median stripe was accurate, and that this stripe is not posteriorly expanded in P. phelpsorum .

Myers and Donnelly (1996: 30–31) took what they could from Lancini’s overly brief description of the phelpsorum holotype (which is lost according to verbal communication from Alfredo Paolillo) and pointed out similarities with goeleti . The only differences were the obvious one in adult middorsal­stripe width, a slight difference in dorsalscale count (40 in one phelpsorum , 33–38 in six goeleti ), a possibly subjective difference in degree of keeling, and an apparent difference in ventral coloration.

Only the last character above was used as a secondary diagnostic character for differentiating goeleti from phelpsorum , and it de­ pended on an interpretation of Lancini’s description. As also noted by Gorzula and Señaris (1999: 141), Lancini ‘‘did not describe the ventral color of the body, but simply stat­ ed that it was similar to that of the tail which was ‘ gris plomizo salpicado de negro ’ (slate gray with black speckling).’’ In contrast, topotypic adult female goeleti were either white or bluish white under the head, and greenish white on other ventral surfaces, except for a tinge of orange under the tails. Gorzula and Señaris (1999: 141) quoted Gorzula’s fieldnotes describing the ventral coloration of another female from Cerro Yaví as ‘‘pale yellowy brown’’, and then obfuscated the matter by discussing ventral color in juveniles (pale green as described for the juvenile paratopotypes or ‘‘dirty pale grayish green with faint gray dusting’’ in a juvenile male from Cerro Corocoro). Gorzula and Señaris concluded their discussion of ventral color by saying that ‘‘Such variation is not convincing to diagnose a new species.’’

Nonetheless, an adult female ventral color of slate gray in life is suggestive to us of taxonomic difference when compared with a geographically remote population in which female venters are pale greenish white or ‘‘pale yellowy brown’’. But we took Lancini at face value that the throat and venter of the female specimen of phelpsorum were slate gray in life, and assumed that if the ventral ground color in life had been pale he would have said so. If, however, he had misleadingly extrapolated ventral color from the preserved specimen, it would be a different matter, since female goeleti became light gray in preservative ‘‘apparently owing to expansion of melanophores that were not evident in life’’ (Myers and Donnelly, 1996: 27). Obviously, posterior widening of the middorsal stripe—most evident in adults, albeit present in juveniles—is probably the most reliable character for separating Prionodactylus goeleti from P. phelpsorum (fig. 43). The absence of a middorsal stripe seems to distinguish a third tepui species, as discussed below.

Gorzula and Señaris (1999: 129–139) described Prionodactylus nigroventris from 1650 m elevation on Cerro Guanay, a neighboring tepui immediately to the northwest of the Yutaje´–Corocoro massif (fig. 1). The type series of P. nigroventris comprised one adult male, a subadult male, and a subadult female. The new species was compared with P. goeleti (as ‘‘ phelpsorum ’’)—its nearest geographic relative—only in the Diagnosis, where P. nigroventris was said to differ by having a ‘‘dark black venter in adult males (orange in P. phelpsorum ) and 6 to 9 rows of temporals between the middle postocular and the scales bordering the ear opening.’’

The comparison of the black venter of adult male nigroventris with the orange venter of adult male phelpsorum seems based on two specimens —the nigroventris holotype and our earlier description of a male goeleti , which developed extensive black ventral coloration after preservation (Myers and Donnelly, 1996: fig. 18, lower right). Concerning the temporal scales, Gorzula and Señaris did not give data for phelpsorum / goeleti , but lateral head drawings of two nigroventris do not show the temporal scales as being clearly organized in rows. However, the lateral head views shown by Gorzula and Señaris (1999: figs. 17b, 18b) for P. nigroventris do bear some resemblance to a drawing of P. goeleti , which was described as having the ‘‘Temporal region between postoculars and ear opening with about 15–25 irregularly shaped juxtaposed scales, of which the upper ones are large and the lower ones small to medium in relative size’’ (Myers and Donnelly, 1996: 26 and fig. 17). The smallest scales are wedged obliquely from near the postoculars toward the corner of the mouth. But there are other characters not discussed.

Examination of the description of P. nigroventris reveals an especially striking difference between it and the other tepui species (i.e., P. goeleti and P. phelpsorum [as well as the extralimital P. vertebralis , fig. 42, bottom]). Prionodactylus nigroventris evidently lacks the pale middorsal stripe that is so conspicuous in the other species! We admittedly extrapolate, since Gorzula and Señaris neither published a photograph nor explicitly stated that nigroventris lacks a pale middorsal stripe, but its absence has to be assumed from their description: In life, ‘‘Dorsum of head dark brown. Dorsal scales brown, slightly lighter than the head. Dorsolateral scales greenish yellow, forming two dorsolateral lines’’ (Gorzula and Señaris, 1999: 137).

Therefore, as described by Gorzula and Señaris, the dorsal color pattern of their Prionodactylus nigroventris seems to be much like that of the generic type species, P. manicatus (fig. 42, middle) from western South America. The absence of a median stripe should immediately separate P. nigroventris from the other two tepui species.

FAMILY TROPIDURIDAE

Only one species of tropidurid lizard was obtained by the 1995 AMNH–TERRAMAR Expedition. It is close to a species that we previously named in the genus Plica (Donnelly and Myers, 1991) , which subsequently was placed in the synonymy of Tropidurus by Frost (1992).

Figures

Fig. 31. Adercosaurus vixadnexus, new species. Views of the holotype in life (EBRG 31263, 55 mm SVL).

Fig. 32. Adercosaurus vixadnexus, new species. Dorsal, ventral, and radiographic views of the preserved holotype (EBRG 31263), Χ1.6. Approximately the distal third of the tail is regenerated, as shown by the cartilaginous rod in the radiograph, although there is no clear external evidence of this.

Fig. 33. Tongue of Adercosaurus vixadnexus, new species (holotype).

Fig. 34. Adercosaurus vixadnexus, new species. Dorsal, ventral, and lateral views of head of holotype (EBRG 31263). Scale line = 5 mm.

Fig. 35. Adercosaurus vixadnexus, new species (holotype). Details of gular–pectoral (left) and subpelvic (right) regions.

Fig. 36. Adercosaurus vixadnexus, new species (holotype). Dorsal midbody scales (anterior is left), Χ18. An odd, nonmucronate rectangular scale is visible in the lower right quadrant.

Fig. 37. Caudal scutellation in dorsal view (anterior is left). Top: Adercosaurus vixadnexus, new species (holotype), showing scales arranged in transverse rows only; there is no paramedian series along a vertebral suture. Bottom: Ptychoglossus plicatus (AMNH 1143073, Panama), showing supracaudals arranged in both transverse and longitudinal rows; arrows indicate vertebral suture separating paramedian series.

Fig. 40. Possible interpopulational difference in width of pale middorsal stripe in juvenile Prionodactylus goeleti (Myers and Donnelly), Χ1.75. Left: Cerro Yutaje´, a juvenile (AMNH 147038) 25 mm SVL. Right: Cerro Yavı´, a juvenile paratopotype (AMNH 141331) 26 mm SVL. The middorsal stripe is narrower in juveniles than in adults, and its posterior widening becomes more noticable in adults (compare with fig. 43); see Taxonomic Notes.

Fig. 41. Possible interpopulational difference in size of midgular scales in Prionodactylus goeleti (Myers and Donnelly). Left: Cerro Yutaje´, a juvenile (AMNH 147038) 25 mm SVL. Right: Cerro Yavı´, a juvenile paratopotype (AMNH 141331) 26 mm SVL.

Fig. 42. Top: Prionodactylus goeleti (Myers and Donnelly), the adult male paratype (AMNH 141329, 50 mm SVL) from Cerro Yavı´, Venezuela. Middle: The generic type species, Prionodactylus manicatus (O’Shaughnessy), an adult female (AMNH 113016, 44 mm SVL) from Cordillera Azul, eastern Peru. Bottom: Prionodactylus vertebralis (O’Shaughnessy), an adult male (AMNH 119368, 64 mm SVL) from Cerro Malı´, on the Panamanian–Colombian border.

Fig. 7. Views of the upper Río Corocoro valley, from the slope above the 1700­m camp (see arrow in fig. 6, bottom). Top: Looking northeastward (upstream) toward the Colostethus locality on far side of river. Bottom: Looking southeastward to helicopter about to sit down in the streambed at camp. The hillside above the 1700­m camp is covered in Tyleria­Stegolepis­Brocchinia scrub growing on rocky soil. Peering uphill (looking for the cameraman who had just called to him), ornithologist George Barrowclough provides a sense of scale for the density and height of the scrub vegetation. See figure 23 for interior views of the mossy gallery forest across the river.