Brazilian scientists have described a new species of tetra of the genus Oligosarcus from Brazil.
The new species, named Oligosarcus perdido by Alexandre Ribeiro, Marcel Cavallaro and "tavio Froehlich, is described in a recent issue of the journal Zootaxa.
Oligosarcus perdido is known from the southern margin of the Pantanal wetland, in the upper Paraguay River drainage, with its specific name derived from the type locality (Rio Perdido).
Oligosarcus perdido can be distinguished from other members of the genus in having 61"63 lateral line scales, 15"20 circumpeduncular scales and the absence of the enlarged foramen on the premaxilla that accommodates the largest dentary tooth when the mouth is closed.
The new species was collected in a karstic region of the southern margin of the Pantanal wetland.
The type locality is a river dammed by calcareous tufa deposits, forming sequences of waterfalls.
The dammed sections are as deep as 12 metres, with vertical rock banks, very slow flow and substrate consisting of numerous logs, branches and whole trees lying on whitish calcareous clay.
The fish were collected in the sluggish- to still-water stretches of the river. The adult fish appeared to be active from dusk until about 9:00 pm.
For more information, see the paper: Ribeiro, AC, MR Cavallaro and " Froehlich (2007) Oligosarcus perdido(Characiformes, Characidae), a new species of freshwater fish from Serra da Bodoquena, upper Rio Paraguai basin, Brazil. Zootaxa 1560, 43"53.