The catfish Heptapterus collettii has often puzzled scientists, as it has an unusual set of features for a South American catfish.
Now, after 123 years, ichthyologists have finally worked out why.
According to a new paper published in the journal Copeia, Heptapterus collettii is not in fact in a member of the neotropical Heptapteridae family, or indeed any other South American catfish family, as it isn't actually from South America at all.
Flavio Bockmann and Mario de Pinna say that the catfish, which was supposedly described from specimens caught in the La Plata basin, actually has all the features of a member of the south Asian family Olyridae.
They reckon that the mistakenly identified catfish is actually a close relative of Olyra longicaudata, and suggest calling the fish Olyra collettii to reflect this.
Since it's extremely unlikely that there's an Olyra species so similar living on the other side of the world, it appears that the locality records accidentally got muddled up when the fish was originally described.
For more details read the paper: Bockmann, FA and MCC de Pinna. (2004) - Heptapterus collettii Steindacher 1881: A Member of the Asian Bagrid Genus Olyra Erroneously Assigned to the Neotropical Fauna (Siluriformes: Ostariophysi). Copeia, Vol. 2004, No. 3, pp. 665-675.