Scientists from Brazil and Argentina have described a new species of fossil cichlid from Argentina in the most recent issue of the Journal of Vertebrate Paleonotology.
The fossil cichlid, named Gymnogeophagus eocenicus, comes from the early to middle Eocene (ca. 37–56 million years ago) of northwestern Argentina.
Based on other fossils found in the area, the habitat that G. eocenicus inhabited was thought to be a relatively shallow freshwater lake (a habitat type that many modern congeners inhabit).
Because Gymnogeophagus are considered to be relatively derived cichlids and because the fossil is found in an area within the present-day distribution of the genus (Gymnogeophagus are restricted to southern South America), this discovery implies that the patterns of distribution and endemism of the Neotropical freshwater fish fauna have had a very long history on the continent.
For more information, see the paper: Malabarba, MC, LR Malabarba, and C Del Papa (2010) Gymnogeophagus eocenicus, n. sp. (Perciformes: Cichlidae), an Eocene cichlid from the Lumbrera Formation in Argentina. Journal of Vertebrate Paleontology 30, pp. 341–350.