New North American cyprinid genus described

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Scientists from the USA and Mexico have described a new North American cyprinid genus in a recent issue of the journal Molecular Phylogenetics and Evolution.

The new genus, named Tampichthys, was described as part of a study on the molecular phylogeny of the North American cyprinid genus Dionda by Susana Schnhuth, Ignacio Doadrio, Omar Dominguez-Dominguez, David Hillis and Richard Mayden.

The authors used one mitochondrial (cytb) and three nuclear gene sequences (S7, Rhodopsin, Rag1) totaling 4487 nucleotides to examine the phylogenetic relationships of 15 species of Dionda and 34 species of closely-related North American cyprinids.

The authors found that members of the genus Dionda were not monophyletic, with six species (D. rasconis, D. ipni, D. erimyzonops, D. mandibuaris, D. dichromus and D. catostomops) being more closely related to another genus (Codoma) than to all other species of Dionda.

These six species, which occur in east-central Mexico (principally inhabiting the upper waters of the Pnuco"Tames drainage), were thus described as belonging to a new genus, Tampichthys. The name of the genus means fish from the Tampico Embayment drainage of Mexico in Greek.

Tampichthys is physically distinguished from other North American cyprinid genera by the combination of: a lateral dark stripe followed by black spot on caudal fin origin, coiled long-gutted intestine, black peritoneum with silvery base, small U-shaped sub-terminal mouth, complete lateral line, tubercles in breeding males, 8 anal rays, well hooked pharyngeal teeth in one row 4"4, head size from 3.5 to 4 times the standard length and dorsal fin origin over to well behind pelvic origin.

However, the authors note that orphological differentiation of species of Tampichthys from species of Dionda sensu stricto, however, are less consistent. Few morphological characters consistently differentiate Tampichthys from Dionda, despite the fact that these genera are highly differentiated on the basis of molecular evidence and are not close relatives

For more information, see the paper: Schnhuth, S, I Doadrio, O Dominguez-Dominguez, DM Hillis and RL Mayden (2008) Molecular evolution of southern North American Cyprinidae (Actinopterygii), with the description of the new genus Tampichthys from central Mexico. Molecular Phylogenetics and Evolution 47, pp. 729"756.