A new Corydoras from floodplain swamps of the São Francisco river basin, northeastern Brazil: Corydoras costai

[Acanthicus]

ABSTRACT
Corydoras costai is a new species described from seasonal swamps adjacent to the upper Rãs river of the Caatinga, tributary of the São Francisco river basin, northeastern Brazil. The new species, as well as C. difluviatilis, differ from all other Corydoradinae by having parapophyses of fourth free vertebra reduced and separated from each other, not fused into a haemal arch. Corydoras costai shares a unique colour pattern with C. garbei and C. difluviatilis, differing from both C. garbei and C. difluviatilis by having fewer rib pairs; from C. garbei by having odontodes present on infraorbitals and opercle, and nuchal plate not in contact with supraoccipital plate; and differing from C. difluviatilis by having five well delimited large dark brown blotches from the caudal fin base to the posterior margin of opercle, along the junction of dorsal and ventral plates on the midline of body, lower region of cleithrum dark brown, first haemal arch present on sixth free vertebra, fewer precaudal vertebra, fewer not segmented rays on anal fin, a shorter head and a deeper head. The new species shares with Corydoras difluviatilis the lack of contact between the supraoccipital and nuchal plate, small degree of ossification of the second hypobranchial and large mesial expansions on the first and second infraorbitals; which suggest a basal position within the Corydoradinae. The serrations on posterior margin of pectoral*-fin spine revealed to be a polymorphic character in C. costai.

Quelle: https://www.pfeil-verlag.de/04biol/pdf/spix39_1_21.pdf