Brazilian scientists have described a new species of Hyphessobrycon tetra from Venezuela with hooks on the anal-fin rays of adult males in a recent issue of the journal Zootaxa.
The new tetra, named Hyphessobrycon otrynus by authors Ricardo Benine and Guilherme Lopes, is known only from the tributaries of the Portuguesa River drainage (itself part of the Orinoco River drainage) in Venezuela.
Hyphessobrycon otrynus can be distinguished from other members of the genus except for H.diancistrus in having two very large bony hooks curving dorsally on each side of the anal fin in adult males, and a black distal third of the caudal fin rays.
It differs from H. otrynus in having more branched anal-fin rays (19"21 vs. 14) and in a different position of the bony hooks on the anal-fin rays of adult males (on the fourth or fifth segments of the last unbranched anal-fin ray and on the fifth segment of the first branched anal-fin ray in H. otrynus vs. the first and third segments of the last unbranched and first branched anal-fin rays in H. diancistrus).
The species is named after the spur-like hooks on the anal-fin rays (Greek otrynus, meaning spur).
For more information, see the paper: Benine, RC and GAM Lopes (2008) A new species of Hyphessobrycon (Characiformes: Characidae) from ro Portuguesa, ro Orinoco basin, Venezuela. Zootaxa 1747, pp. 61"68.