Revision of †Ellimmichthys longicostatus (Clupeomorpha: †Ellimmichthyiformes) from the Lower Cretaceous of Brazil with comments on the taxonomy of related species

Abstract

†Ellimmichthys longicostatus is a deep-bodied and double-armored clupeomorph fish only known from non-marine Berriasian-Valanginian beds of the Recôncavo Basin, northeastern Brazil. It is the oldest herring-like fossil fish described from South America. This species was recently separated in two distinct forms that have not yet been formally classified: the first has the pelvic fin anterior to the origin of the dorsal fin, enlarged, thorn-shaped postpelvic scutes, posteriormost ribs on parapophyses, and long dorsal pterygiophores; the second one has the pelvic fin opposite the base of the dorsal fin and all the ribs inserted in deep excavations on centra. The latter corresponds to the fish used as a reference by Edward Drinker Cope, in 1886, in the original description of the species and herein referred as †Ellimmichthys longicostatus s. str. Consequently, the current diagnosis of †Ellimmichthys is not sufficient to distinguish species and closely related taxa. Based on new and old articulated specimens, we provide an amended diagnosis for †Ellimmichthys longicostatus s. str. and erect †Ellimmichthys spinosus nov. sp. for the rare form that was mistakenly identified to be the same species.