new species:
Hyphessobrycon nicolasi Miquelarena & López, 2010

type locality:
Argentina, province of Entre Rios, El Pelado stream, tributary of Uruguay River in the vicinity of the city of Colón (32º19’S – 58º14’W); holotype: ILPLA 1808 (49,1 mm SL, female), paratypes: ILPLA 1809 (20), 1810 (6), 1811 (8), MLP 9746 (9)

published in:
Miquelarena, A.M. & H.L. López (2010):
Hyphessobrycon nicolasi (Teleostei: Characidae) a new species from the Uruguay River basin in the Mesopotamian Region, Argentina.
Neotropical Ichthyology 8 (1): 1-6

abstract (from publication):
Hyphessobrycon nicolasi is described from the Uruguay River basin in the Mesopotamian Region, Entre Ríos, Argentina. The new species can be distinguished from all congeners by the presence of a well-defined oblique and marginal black stripe on each lobe of the caudal fin. Other characters defining H. nicolasi are the possession of 1-3 teeth with 3-10 cusps on maxilla; outer premaxillary row with 2-3 small teeth, with 5 or 7 cusps; iv-vi, 27-36 anal-fin rays; 33-36 scales on the longitudinal series; two vertical dark spots on the humeral region; dorsal and anal fins dappled in black and base of caudal fin bearing conspicuous black spot; and the presence of bony hooks on the rays of dorsal, anal and caudal fins of the mature males.

habitat notes (from publication):
At the type locality, El Pelado stream has clear water and rocky/sandy bottom, with irregularly distributed small stones, cobbles and boulders. The stream has shallower sectors with fast-running water up to 60 cm deep, and deeper portions with around 2 m depth and abundant submerged vegetation. Species collected with H. nicolasi were Apareiodon affinis, Australoheros scitulus, Cnesterodon decemmaculatus, Corydoras paleatus, Crenicichla lepidota, Cyphocharax spilotus, C. voga, Characidium rachovii, C. tenue, Charax stenopterus, Cheirodon interruptus, Diapoma terofali, Heptapterus mustelinus, Hypostomus commersoni, Loricariichthys anus, Macropsobrycon uruguayanae, Oligosarcus jenynsii, Pseudocorynopoma doriae, and Rineloricaria isaaci.