Lophiobrycon, Castro & Ribeiro & Benine & Melo, 2003

Castro, Ricardo M. C., Ribeiro, Alexandre C., Benine, Ricardo C. & Melo, Alex L. A., 2003, Lophiobrycon weitzmani, a new genus and species of glandulocaudine fish (Characiformes: Characidae) from the rio Grande drainage, upper rio Paraná system, southeastern Brazil, Neotropical Ichthyology 1 (1), pp. 11-19 : 13-14

Lophiobrycon , new genus

Type species: Lophiobrycon weitzmani by monotypy and original designation.

Diagnosis. The tribe Glandulocaudini was diagnosed by Weitzman & Menezes (1998: 183) on the basis of three characters: 1) the scales of the dorsal caudal-fin lobe with a derived morphology and extending posteriorly to cover all or part of the caudal organ; 2) the presence of a caudal finray pump of a kind unique to the tribe; and 3) the pored lateral line abbreviated and consisting of 3-7 scales with the terminal lateral-line tube absent. The inclusion of Lophiobrycon somewhat modifies this diagnosis because that genus lacks the modified dorsal caudal scales (a plesiomorphic feature) characteristic of members of the other glandulocaudine tribes ( Fig. 4 ).

Lophiobrycon can be further distinguished from all other species of the Glandulocaudini in possessing the following autapomorphies: 1) anterior tip of pelvic bone located between or slightly anterior to ventral tips of anterior two pleural ribs in lateral view, versus ventral to ventral tips of second to third pleural ribs, anterior to ventral tip of first pleural rib, or laying near cleithrum; 2) posteromedial (parietal) branch of supraorbital (frontal) sensory canal reduced in length and never extending into parietal bone, versus sensory canal extending posteriorly into parietal bone; and 3) latero-sensory canal of posttemporal bone present, versus absent.

Additional autapomorphic diagnostic characters for the new genus not included in the analysis are: 1) the length of adult male adipose-fin base extends for almost the entire distance between the posterior termination of the base of the dorsal-fin and the base of the upper lobe of the caudal fin, its length averaging approximately 25% of SL ( Figs. 1A and 2 ); and 2) middle portions of the unbranched and first branched pectoral-fin rays with globular expansions formed by the lepidotrichia and hypertrophied soft tissue ( Fig. 5 ).

Etymology. The name Lophiobrycon is from the Greek lophia (= crest, used in reference to the uniquely elongate and crest-shaped adipose-fin of mature males) and brycho (= to gnash the teeth, in reference to the characid genus Brycon , hence a characid fish).

Figures

Fig. 4. Lophiobrycon weitzmani, paratype, LIRP 4338, 24.7 mm SL, squamation of central and basal region of caudal fin of adult male, left side, anterior at left. Arrows indicates the basely straight principal caudal-fin rays 11 (above) and 12 (below) supporting a concentration of bead like hypertrophied glandular tissue (not shown in the illustration) along the borders of its proximal portions.

Fig. 1. Lophiobrycon weitzmani, holotype (A), LIRP 4366, male, SL 26.0 mm; paratype (B), LIRP 4338, female, SL 27.0 mm; Brazil, Minas Gerais, rio Grande basin, Município de Delfinópolis, Estância Carmem Sílvia, córrego Bom Jesus (20º12’10’’S 46º55’22”W), showing the accentuated sexual dimorphism in general body shape and adipose-fin dimensions.

Fig. 2. Lophiobrycon weitzmani, paratype, LIRP 4338, male, SL 31.1 mm; Brazil, Minas Gerais, rio Grande basin, Município de Delfinópolis, Estância Carmem Sílvia, córrego Bom Jesus, (20º12’10’’S 46º55’22”W), aquarium field photograph.

Fig. 5. Lophiobrycon weitzmani, paratype, alizarin stained pectoral fin of adult male, ventral view, anteriormost fin ray at top, medial fin ray at bottom. Arrow indicates modified portions of the lepidotrichia supporting the diagnostic globular expansion, formed by the lepidotrichia and hypertrophied soft tissue (not represented in the illustration), in the middle portions of the unbranched (above) and first branched (below) pectoral-fin rays. LIRP 4338, 24.7 mm SL, same locality data as in Figs. 1 and 3.