Willian Massaharu Ohara

Hyphessobrycon lucenorum (Characiformes: Characidae) , a new species from the rio Madeira basin, Rondônia State, Brazil

A new species of characid is described from the upper rio Machado, a tributary of the rio Madeira basin, Rondônia, Brazil. Hyphessobrycon lucenorum can be distinguished from all congeners by the unique combination of the presence of a conspicuous rounded humeral blotch and a broad and diffuse longitudinal stripe. The new species is included within the Hyphessobrycon agulha group. The high number of endemic species of fishes occurring in the headwater tributaries of three river systems (rio Madeira, rio Tapajós, and rio Paraguai) draining the watershed defined by the Chapada dos Parecis is discussed.

Jupiaba citrina, a new species from rio Aripuanã, rio Madeira basin, Amazonas and Mato Grosso States, Brazil (Characiformes: Characidae)

A new species of Jupiaba Zanata is described from tributaries of the rio Aripuana, rio Madeira basin, Amazonas and Mato Grosso States, Brazil. The new species can be diagnosed from its congeners (except J. abramoides, J. anteroides, and J. poranga) by having two vertically-elongated humeral blotches, the anterior usually with a darker median portion forming an horizontally-elongated trace pointed anteriorly, and a well defined dark longitudinal line extending from the second humeral blotch to the caudal peduncle. The new species differs from J. abramoides, J. anteroides, and J. poranga by having an elongated blotch over caudal peduncle that extends to the distal tip of the caudal-fin median rays. Also, it can be distinguished from most congeners by the combination of relatively high number of lateral line scales, predorsal median line without a series of scales, dentary teeth decreasing abruptly in size towards posterior portion, and presence of a larger central teeth cusp.

A new species of Hyphessobrycon Durbin (Characiformes: Characidae) from rio Aripuanã, rio Madeira basin, Brazil

A new species of Hyphessobrycon is described from the rio Aripuanã, rio Madeira basin, Amazonas State, Brazil. Hyphessobrycon procyon can be distinguished from its congeners by the unique combination of the following features: elongation of the dorsal fin in mature males, absence of dark blotches on the dorsal fin, and presence of two humeral blotches. The possibility of a relationship of the new species within H. elachys, H. heliacus, H. loweae, H. moniliger, and H. peugeoti is discussed based on the sharing of characteristics related to the sexual dimorphism and tooth morphology.

A new species of Characidium Reinhardt (Ostariophysi: Characiformes: Crenuchidae) from headwaters of rio Pacaás Novos, rio Madeira basin, Rondônia, Brazil

Characidium summus, new species, is described from rio Pacaás Novos, rio Madeira basin, Rondônia, Brazil. The new species is the unique among congeners for completely lacking an adipose fin and having a complete lateral line. Characidium summus can be further distinguished from congeners, including C. vestigipinne that also has a complete lateral line and adipose fin absent, vestigial or reduced by the absence of dark bars or spots on head, body or fins, except for a dark blotch on the rear of the opercle, a narrow midlateral dark stripe, and a dark basicaudal spot. In addition, C. summus possess a vestigial supraorbital and a remarkably small pseutotympanum. The possible mimetic relationship between the new species with Erythrinus erythrinus is discussed.

Hyphessobrycon petricolus , a new species of tetra (Characiformes: Characidae) from the rio Madeira basin, Mato Grosso, Brazil

A new species of Hyphessobrycon is described from the rio Roosevelt, rio Madeira basin, Mato Grosso State, Brazil. Hyphessobrycon petricolus sp. n. can be distinguished from its congeners by the unique combination of the following features: a well-defined, relatively narrow dark midlateral stripe on body extending from immediately behind posterior margin of opercle to the middle caudal-fin rays, relatively conspicuous humeral blotch, and 16-20 branched anal-fin rays. Comments on the remaining Hyphessobrycon species presenting a conspicuous dark midlateral stripe are presented.

Phycocharax rasbora, a new genus and species of Brazilian tetra (Characiformes: Characidae) from Serra do Cachimbo, rio Tapajós basin

A new genus and species of characid fish is described from rio Braço Norte, a tributary of rio Teles Pires, Tapajós basin, Mato Groso, Brazil. The new taxa can be diagnosed from the remaining characids by a unique combination of characters that includes the presence of a single row of relatively compressed premaxillary teeth, large teeth with four to nine cusps on premaxillary and dentary, absence of pseudotympanum, incomplete lateral line with 7–13 pored scales, sexually-dimorphic males with distal margin of anal fin approximately straight, and presence of a nearly triangular and horizontally elongated blotch from the posterior half of the body to caudal peduncle. The most parsimonious phylogenetic hypothesis, using morphological data, recovered the new genus and species in a clade including Paracheirodon axelrodi and Hyphessobrycon elachys.

Wrapped in flames: Corydoras hephaestus , a new remarkably colored species from the Rio Madeira basin (Teleostei: Callichthyidae)

A new species of Corydoras is described from the upper Rio Machado, Rio Madeira basin, Rondônia State, Brazil. The new species can be distinguished from its congeners by the absence of contact between the posterior process of the parieto-supraoccipital and the nuchal plate; a ventral laminar expansion of the infraorbital 1 conspicuously developed; and the posterior margin of the pectoral-fin spine with serrations along almost of its entire length, only lacking in the distal portion. Additionally, Corydoras hephaestus possesses dorsal and pectoral spines short, and exhibits an unusual color pattern in life. The conservation status of the new species and other endemic species are briefly commented.

A new long-snouted species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the rio Madeira basin

A new species of Corydoras is described from the rio Aripuanã, rio Madeira basin, Mato Grosso State, Brazil. The new species can be distinguished from its congeners by the presence of the following features: long mesethmoid, with anterior tip well developed, conspicuously larger than 50% of bone length; posterior margin of dorsal-fin spine with serrations directed towards tip of spine; one to two longitudinal black stripes on flanks; absence of a black blotch across the eyes (mask); absence of a large black blotch on dorsal fin; and transversal black bars on caudal fin. Comments on endemism in interfluvial region between Madeira and Tapajós rivers are briefly discussed.

Two new species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the rio Madeira basin, Brazil

Two new species of Corydoras are described from the rio Madeira basin, Brazil. The intermediate long-snouted new species can be distinguished from its congeners by presenting the following combination of features: posterior margin of dorsal-fin spine with laminar serrations directed towards the origin of the spine; presence of two longitudinal black stripes on flanks; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; absence of a conspicuous black marbled coloration pattern on head; black spots on caudal fin, some spots arranged, forming transversal bars; and brownish dorsal-fin spine. The short-snouted new speciescan be distinguished from its congeners by the following combination of features: short mesethmoid; posterior laminar expansion of infraorbital 2 very reduced, not in contact with compound pterotic; two or three longitudinal black stripes on flanks; absence of an oblique or vertical black blotch across the eye; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; and ventral surface of trunk naked or covered by sparse platelets.

Hyphessobrycon platyodus (Teleostei: Characiformes), a new species from the Rio Madeira basin, Brazil, with comments on how multicuspid teeth relate to feeding habits in Characidae

A new species of Hyphessobrycon is described from the Rio Juma, a tributary of the lower Rio Aripuanã-Rio Madeira basin, Amazonas, Brazil. Hyphessobrycon platyodus can be distinguished from its congeners by the: presence of an elongated dorsal fin in adult males, 25-28 branched anal-fin rays and absence of dark blotches from the dorsal fin and caudal peduncle. The presence of multicuspid teeth in species of Characidae and its relation with feeding habits are briefly commented on.