Pantepuisaurus

Kok, Philippe J. R., 2009, Lizard in the clouds: a new highland genus and species of Gymnophthalmidae (Reptilia: Squamata) from Maringma tepui, western Guyana, Zootaxa 1992, pp. 53-67 : 54-56

Pantepuisaurus genus novum

Type species. Pantepuisaurus rodriguesi species novum

Etymology. A noun in apposition, derived from “Pantepui” referring to the phytogeographic province where the type species was discovered, and the Greek sauros meaning “lizard”. Gender masculine.

Content. Pantepuisaurus rodriguesi species novum; monotypic.

Diagnosis. An elongate gymnophthalmid (known SVL in male 58.3 mm) with a long tail (1.6x SVL) and the unique following combination of characters: (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, (5) frontoparietals, parietals and interparietal present, (6) parietals and interparietal longer than wide, (7) interparietal and parietals forming a jagged, irregular posterior margin, (8) occipitals present, (9) three pairs of genials, second pair in contact with only one infralabial, (10) enlarged median pairs of gulars, (11) dorsal scales hexagonal, keeled, in transverse rows only, (12) ventral scales imbricate, hexagonal, mucronate, broadly keeled, in transverse rows only, (13) tongue anterodorsally covered by oblique, anteriorly converging plicae, posterodorsally covered by large scalelike papillae (14) hemipenis weakly bilobed with series of curved transverse plicae bearing mineralized spicules.

Pantepuisaurus differs from members of Alopoglossinae in having the tongue anterodorsally covered by oblique plicae and posterodorsally covered by large scalelike papillae (entirely covered by oblique plicae in Alopoglossinae), the interparietal and the parietals forming a jagged, irregular line (straight posterior margin), and in having ventral scales in transverse rows only (in transverse and longitudinal rows in Alopoglossinae); from members of Gymnophthalminae in having hands pentadactyl with the first finger clawed (first finger absent, reduced and/or clawless in Gymnophthalminae); from Rhachisaurinae in having external ear openings (absent in Rhachisaurinae). Within Cercosaurinae (sensu Pellegrino et al. 2001 and Rodrigues et al. 2005), Pantepuisaurus differs from all genera except Ecpleopus and Leposoma of the scincoides group in having hexagonal, mucronate ventral scales arranged in transverse rows only. Pantepuisaurus is readily distinguished from Ecpleopus (characters of Ecpleopus in parentheses) notably by the presence of a broad keel on ventrals (absent), quadrangular gular scales (mucronate), complete superciliary series (incomplete), and the presence of femoral pores in males (absent). Pantepuisaurus is quickly separated from Leposoma of the scincoides group (characters of Leposoma in parentheses) in having quadrangular gular scales (mucronate), by the absence of distinct striations on head scales (present), the interparietal and the parietals forming a jagged, irregular line (round posterior margin), and the presence of occipitals (absent). Two additional gymnophthalmid genera, Adercosaurus and Kaieteurosaurus , have not been assigned to any subfamily yet, but might be related each other and with Pantepuisaurus . Pantepuisaurus is immediately distinguished from Adercosaurus (characters of Adercosaurus in parentheses) in having imbricate, hexagonal, mucronate, broadly keeled ventral scales in transverse rows only (smooth, in transverse and longitudinal rows), in having a highly reduced fourth infralabial (not reduced) and the second pair of genials partly separated from the infralabials and in contact with one infralabial only (not separated from the infralabials, in contact with two infralabials), in lacking oblique plicae at the rear of the tongue, which is posteriorly covered by large scalelike papillae (rear of tongue covered by oblique plicae), and in having mineralized spicules on hemipenes’ plicae (absent). Pantepuisaurus is most similar to Kaieteurosaurus in having hexagonal, mucronate ventral scales arranged in transverse rows only, but it is readily distinguished from it (characters of Kaieteurosaurus in parentheses) by the presence of prefrontal scales (absent), three pairs of genials (two), in having a highly reduced fourth infralabial (not reduced) and the second pair of genials partly separated from the infralabials and in contact with one infralabial only (not separated from the infralabials, in contact with two infralabials), the common suture of the interparietal and parietals forming a jagged, irregular line (more or less straight posterior margin), an entire nasal (divided), and the aspect of the ventral scales that are much less lanceolate and mucronate than in Kaieteurosaurus . It should be emphasized here that Kaieteurosaurus also has broad “keels” on ventral scales (i.e. the central part of the scale is broadly elevated), a character that was only noticed while closely comparing the two genera. This character is not conspicuous in all Kaieteurosaurus specimens and is mostly noticeable on anteriormost and posteriormost ventral scales. In Kaieteurosaurus the significant lateral extension of the flat “keel” gives a lanceolate, smooth, “unkeeled” aspect to the ventral scales as described by Kok (2005), while the keel is more prominent and conspicuous in Pantepuisaurus . Figure 4 schematically illustrates the difference in the aspect of the broad keel on ventral scales between Pantepuisaurus and Kaieteurosaurus . A summary of main diagnostic characters for Pantepuisaurus , Adercosaurus and Kaieteurosaurus is in Table 1 .

Distribution. The genus is currently known only from the type locality, the summit of Maringma tepui in Guyana ( Fig. 1 ).

Taxonomic comments. No less than eight new gymnophthalmid genera have been described ( Myers & Donnelly 2001, Doan & Castoe 2005, Kok 2005, Rodrigues et al. 2005, 2007, Rodrigues & Maranhão dos Santos 2008) since the molecular-based phylogenetic hypothesis of Pellegrino et al. (2001), who demonstrated the monophyly of Gymnophthalmidae . Some higher-level taxonomic changes are still in debate (see Castoe et al. 2004, Rodrigues et al. 2007) and refinement of higher-level taxonomy of gymnophthalmids is still necessary.

Morphologically, the new genus shows some similarities with Adercosaurus and Kaieteurosaurus . Giving the low number of specimens available, any speculation on the relationships between Adercosaurus (known only from the holotype), Kaieteurosaurus (known only from three specimens), and Pantepuisaurus (known only from the holotype) seems premature. More specimens of these three genera are clearly needed to elucidate relationships between them. However, preliminary molecular analysis and comparisons do indicate affinities between Pantepuisaurus and Kaieteurosaurus (unfortunately, molecular data on Adercosaurus are not available), but reveal significant genetic divergences between these two genera that give further support to the erection of a new genus. Molecular analysis also suggests assignment of Pantepuisaurus and Kaieteurosaurus to the tribe Ecpleopini (Cercosaurinae) (M. T. Rodrigues, pers. comm.).

A more “conservative” attitude would have been to accommodate the new species in an already known monotypic genus sharing some morphological similarities (i.e. Adercosaurus or Kaieteurosaurus ). However this would have given rise to two important problems: (1) assignment of the new species to either of these two genera would have been arbitrary and poorly supported because the new species differs from both of them in a combination of important characteristics currently used to diagnose gymnophthalmid genera (e.g. condition of the posterior margin of the interparietal and parietals, condition of ventral scales, number of genials, presence of prefrontals, hemipenial morphology, tongue morphology) (2) because the new species differs from these two genera in morphological characteristics used to separate other genera (especially in the tribe Ecpleopini), placing the new species in one of them would have rendered the taxonomic status of these and other genera dubious by suggesting that these characters are variable intragenerically (thus making taxonomy of the group more complicated instead of simplifying it). One could suggest that Kaieteurosaurus is a synonym of Adercosaurus , however this is not supported by any evidence, these two genera being differentiated on the basis of many important diagnostic characters (see Kok 2005).

Figures

FIGURE 1. Area map of Mount Maringma showing the type locality of Pantepuisaurus rodriguesi gen. nov. sp. nov. (red 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 4. Schematic illustration of the ventral scale condition in Pantepuisaurus gen. nov. and Kaieteurosaurus. A: Four posterior ventral scales of Pantepuisaurus rodriguesi gen. nov. sp. nov. showing the broad keel (in white). B: Four posterior ventral scales of Kaieteurosaurus hindsi showing the broad keel (in white) that significantly extends laterally giving an aspect of smooth unkeeled lanceolate ventrals. Drawings are not at scale.