Pterolebias Garman

Wilson J. E. M. Costa, 2005, The Neotropical annual killifish genus Pterolebias Garman (Teleostei: Cyprinodontiformes: Rivulidae): phylogenetic relationships, descriptive morphology, and taxonomic revision., Zootaxa 1067, pp. 1-36 : 8-13

Pterolebias Garman

Pterolebias Garman, 1895 : 141 (type species: Pterolebias longipinnis Garman, 1895 ; type by monotypy).

Diagnosis: Pterolebias differs from all other genera of Rivulidae in possessing a narrow and pointed ventral process of angulo-articular, an expanded medial flap on the second pharyngobranchial, small humeral metallic orange spots in males, and dark gray bars on the pectoral fin in males. Other derived characters shared by the species of Pterolebias but hypothesized to be independently acquired in other rivulid lineages are: distal portion of maxilla strongly twisted, long posterior process of quadrate, and a narrow and long basihyal.

Osteology. Superficial dermal bones and neurocranium (Figs. 2a-d): Nasal thin, scalelike. Lacrymal thin and twisted, almost cylindrical, without posterior extensions. Dermosphenotic thin and ovoid, its outer surface gently concave.

Neurocranium depressed. Dorsal surface with thin ossification, bones with unclear limits. Frontal approximately rectangular, with short lateral borders. Parietal subtriangular. Supraoccipital with narrow, paired posterior process, its tip near neural spine of first vertebra. Lateral process of sphenotic narrow. Limits of bones along ventral surface of neurocranium conspicuous. Vomer trapezoidal with elongated, pointed posterior process. Two to ten conical teeth on anteromedian portion of vomer. Lateral ethmoid with distinctive anterior retrorse process. Anteromedian portion of lateral ethmoid slightly dorsally overlapping lateral portion of vomer, but never abutting lateral surface of anterior process of parasphenoid. Parasphenoid cross-shaped, with two lateral processes. Anterior portion of parasphenoid wide and pointed, overlapping dorsally posterior process of vomer; posterior portion wide and truncate, firmly attached to basioccipital; anteriormost lateral process connected to pterosphenoid; posterior lateral process attached to the prootic.

Jaws, jaw suspensorium, and opercular apparatus (Figs. 2a-c): Jaw bones relatively short. Premaxilla with teeth along medial half of its anterior face; ascending process narrow, approximately rectangular, anterodistal process about trapezoidal. Maxilla rodshaped, strongly twisted in its distal portion, bifid in its medial portion, with subtriangular dorsal process and ventral process bent. Rostral cartilage longer than wide. Dentary with teeth on its distal half. Angulo-articular triangular, with short and pointed ventral process. Retro-articular small. Meckels cartilage elongate. Premaxillary and dentary teeth conical, arranged in irregular rows; most teeth small, some larger ones forming outer row, in which, on middle of row, one or two teeth are strongly laterally displaced.

Autopalatine and ectopterygoid completely fused, forming single structure, in which ventral tip slightly abuts quadrate. Mesopterygoid thin, posteriorly contacting metapterygoid, ventrally overlapping dorsal portion of quadrate, and anterodorsally overlapping autopalatine. Quadrate approximately triangular, with long posterior process, longer that quadrate without posterior process. Sympletic elongate. Metapterygoid wide in its ventral portion, becoming abruptly narrower in its dorsal portion. All opercular apparatus bones thin. Dorsal extremity of opercle and subopercle pointed. Preopercle curved, dorsal portion forming a distinct canal.

Hyoid and branchial arches (Figs. 3d-g): Basihyal subtriangular, longer than space occupied by basibranchials, and narrow, its width about 35-45% of its length; basihyal cartilage short, about 20-25% of basihyal length. Dorsal and ventral hypohyals small, always ossified. Anterior and posterior ceratohyals separated by wide cartilage. Six branchiostegal rays. Interhyal cartilaginous and minute. Urohyal with long anterodorsal process and short anterior process.

Second pharyngobranchial approximately triangular, longer than wide, with prominent medial flap; two to four small conical teeth on proximal border. Third pharyngobranchial with conical teeth. Interarcual cartilage minute. Second pharyngobranchial without subdistal process. Third epibranchial with short uncinate process. Proximal edge of first hypobranchial bifid; cartilage along entire lateral margin of first hypobranchial. Fourth ceratobranchial with small conical teeth along most dorsal surface. Fifth ceratobranchial subtriangular, wide in P. longipinnis and narrow in P. phasianus , with robust conical teeth. Gill-rakers of first branchial arch 2 + 9-10.

Vertebrae and caudal skeleton (Figs. 2d-f): Neural spines of first five vertebrae wider than neural spines of posterior vertebrae. Paired process on anterior subdorsal portion of first vertebra. Base of second epipleural rib wide, often with short dorsal process. Caudal vertebrae with long neural prezygapophyses. Total vertebrae 30-34.

Epural and parhypural with similar shape, proximal portion respectively near neural and hemal spine of preural centrum. Hypurals fused, forming two plates separated by median gap. Accessory caudal cartilages absent.

Dorsal and anal fins (Figs. 4a-b): Males and females with same number of dorsal and anal-fin rays. Most rays branched. Dorsal-fin origin on vertical between 18th and 21st vertebra, anal-fin origin on vertical between 12th and 15th vertebra. Two rays associated with first proximal radial of dorsal fin, and three associated with first proximal radial of anal fin. First dorsal-fin proximal radiais slightly widened on proximal portion, first analfin proximal radiais widened and dorso-posteriorly directed. Middle and distal radiais of dorsal and anal fins ossified.

Shoulder and pelvic girdles (Figs. 4c-d): Dorsal portion of cleithrum short, without posterior flange. Ventral process of posttemporal moderate to long. Posttemporal and supracleithrum co-ossified, limits almost inconspicuous. Prominent keel along posttemporal and supracleithrum. Ventral tip of coracoid dorsoposteriorly placed to ventral tip of cleithrum. Coracoid separated from scapula by narrow cartilage. Proximal radiais of pectoral fin cubic, ventralmost radial with ventrally expanded posterior portion.

Third postcleithrum rod-shaped. Pelvic bones medially in contact, ischial process indistinct.