Potamites Doan & Castoe 2005, GEN. NOV.

POTAMITES GEN. NOV.

Type species: Euspondylus strangulatus Cope, 1868: 99.

Neusticurus strangulatus group: Uzzell, 1966: 311.

Etymology: Potamites is a masculine Greek noun, meaning water finder. It refers to the fact that most members of this genus are semiaquatic, walking on the bottom of streams and often diving into streams to escape predation.

Definition: Tongue with imbricate, scale-like papillae. Nostril pierced in a single nasal; nasals separated usually by paired or single frontonasals, occasionally by irregular scales; prefrontals paired or irregular; interparietal usually bordered by a pair of parietals laterally, by a series of two to eight smaller scales posteriorly; occipital and temporal scales differentiated or not; rostral large, mental and postmental single, followed by several paired chin shields; gular crease feeble or absent. Collar fold well developed. Lower eyelid developed, with a palpebral disc undivided or divided into two to seven scales, transparent or pigmented. Tympanum at surface of head or slightly recessed, overhung by surrounding scales of surface of head. Dorsal scales heterogeneous, imbricate, with large, keeled tubercles intermixed with small flat scales, in transverse or longitudinal rows. Ventral scales wider than dorsals, usually flat, rectangular or slightly rounded posteriorly, subimbricate, in transverse and 6–10 longitudinal rows; lateral rows raised or keeled in some species. Limbs pentadactyl, digits clawed; forefoot with enlarged, plate-like scales along inner margin between thumb and wrist; under side of third and fourth toes with paired scales proximally, inner scale a rounded tubercle. Tail slightly compressed; a double caudal crest, feebly to strongly developed. Total femoral and preanal pores: 10–59 in males; 0–29 in females. Preanal plate in 2–3 rows, posterior row 2–5 scales in both sexes. Males and females with or without conspicuous, white- or browncentred, black-bordered ocelli on their lateral body surfaces. Hemipenis without basal hooks; flounces with minute calcareous spinules.

Diagnosis: Potamites differs from members of subfamily Alopoglossinae by having its tongue covered in imbricate, scale-like papillae instead of oblique plicae (Harris, 1994), from subfamily Gymnophthalminae by having moveable eyelids, from subfamily Rhachisaurinae by having external ear openings and from subfamily Ecpleopinae by having heterogeneous dorsal scalation. Within subfamily Cercosaurinae (sensu Castoe et al., 2004), Potamites differs from all genera except Echinosaura, Neusticurus, and Teuchocercus by having heterogeneous dorsal scalation. It differs from Echinosaura by lacking basal spines on the hemipenes, from Teuchocercus by lacking conical scales on the tail, and from Neusticurus (character states in parentheses) by having a slightly compressed tail (strongly compressed), subimbricate ventral scales (imbricate), and calcareous spinules on flounces of hemipenes (no spinules).

Content: Potamites includes six species (Table 1).

Distribution: Potamites occurs throughout Amazonia in Colombia, Ecuador, Peru, Brazil, and Bolivia and in the San José Province of Costa Rica.