Alternative name Rivulus (Oditichthys) xinguensis.

Rivulus xinguensis was found in the middle section of the lower Xingu River drainage, Estado Para; Municipio de Altamira, eastern Amazon, northern Brazil. The given name refers to the occurrence of this species in this river.

The species was collected by W. Costa assisted by R. Paiva and D. Ramos on 16 June 2004. Coordinates are: 3º 11'59"S; 52º 11'50"W.

Following the description the new species is distinguished from related species as Rivulus urophthalmus, R. stagnatus, R. mazaruni, R. lungi and R. deltaphilus by the number of scales in the longitudinal series having 33-35 (vs. 36-43) and by the absence of well-defined yellow stripes on dorsal and anal margin of caudal fin in males. (vs. present) from R. urophthalmus by the absence of diffuse grey bars on the anterior portion of the flank in males (vs. presence); from R. tocantinensis by having a well developed dermosphenotic (vs. absent, sometimes rudimentary) horizontal red spots on the flank ( vs. rows of wide brownish orange stripes.) and transverse rows of of dark brown dots on the caudal fin in males (vs. large dark orangish brown blotches on the middle of the caudal fin)

It would be interesting to run a DNA sequence on this new species and R. tocantinensis as well and compare them to the R. urophthalmus clade- members mentioned in the description. Results could give a more detailed view on the position of these two species within this clade or may result in exclusion from it.

Their relation and resemblance to the R. R. urophthalmus clade is not to obvious to to me.

The given size is from the samples taken in the wild. It is not known what their maximum size can be after getting adult.

If the size given in the description is their actual adult size the species is more related to other small Rivulus in the Amazon area.

Costa (2011) placed this species in Anablepsoides without proper explanation and by that ignoring the existence of Oditichthys. Til that time it was placed in Oditichthys (Huber 1999) and changed the status from sub-genus to genus status . This move is discussed and not followed in this site.

See for explanation; Page: <Oditichthys> <introduction>

Not known yet, but should be not very different from other members of the genus.

Remarks :

Max. size 0.0 cm.
Dorsal 00.0,
Anal 00.0,
D/A 0.0,
LL scale count (average) 00.0
Pre- dorsal length to % SL – 00.0 %
Depth to % SL – 00.0 %

Costa W.J.E.M, 2010. Two new species of the Rivulus urophthalmus group from the Tocantins and Xingu river drainages, eastern Brazilian Amazon. (Cyprinodontiformes: Rivulidae) Ichthyol. Explor.Freshwaters, Vol. 21, No. 1, pp. 79-85, 2 figs., 1 tab. March 2010.