New genus of headstanding tetras described

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American scientists have named a new genus of headstanding tetras (Anostomidae) in a recent study of its phylogenetic relationships.

Publishing their results in the most recent issue of the Zoological Journal of the Linnean Society, Brian Sidlauskas and Richard Vari name the new genus Petulanos, and distinguish it from other members of the family in having a combination of: strongly upturned mouth, a series of dark spots greater than one scale wide along the lateral line, a series of dark bars across the dorsal surface of the body, four branchiostegal rays, a lack of dermal papillae on the lower lip, two cusps occurring on the symphyseal tooth of the premaxilla, the possession in adults of only a single cusp on the symphyseal and second tooth of the dentary, and the presence of three cusps on the third tooth of the dentary.

The name of the new genus is derived from the Latin petulans (impudent or petulant) and the first four letters of the generic name Anostomus from which Petulanos was separated; both in allusion to the characteristic upturned mouth that gives these fishes the appearance of a perpetual pout.

The recognition of a new genus for three species formerly included within Anostomus (P. intermedius, P. plicatus and P. spiloclistron) follows from a phylogenetic analysis of the Anostomidae based on 152 parsimony-informative morphological characters, in which Anostomus was found to be paraphyletic.

The authors write Laemolyta appeared as sister to the clade containing Anostomus, Gnathodolus, Petulanos, Pseudanos, Sartor and Synaptolaemus. Rhytiodus and Schizodon together formed a well-supported clade that was, in turn, sister to the clade containing Anostomus, Gnathodolus, Laemolyta, Petulanos, Pseudanos, Sartor and Synaptolaemus.

Anostomoides was sister to the clade formed by these nine genera. Leporinus as currently defined was not found to be monophyletic, although certain clades within that genus were supported, including the species with subterminal mouths in the former subgenus Hypomasticus which we recognize herein as a genus. Abramites nested in Leporinus, and Leporellus was found to be the most basal anostomid genus.

For more information, see the paper: Sidlauskas, BL and RP Vari (2008) Phylogenetic relationships within the South American fish family Anostomidae (Teleostei, Ostariophysi, Characiformes). Zoological Journal of the Linnean Society 154, pp. 70"210.