Bulbous-headed knifefish placed in new genus

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Scientists have placed a newly discovered electric fish from South America in a genus of its own.

James Albert and William Crampton described the new apteronotid knifefish in the current volume of Ichthyological Exploration of Freshwaters.

The new fish was discovered in the main Amazon river channel in Brazil and Peru and is unique among apteronotid knifefishes in that its wide head is ventrally flattened, while the body remains slender.

The bulbous-headed knifefish is so different to others in the family that Albert and Crampton were unable to place it in an existing genus; the species has been named Pariosternarchus amazonensis.

NavajiniWhile most apteronotids have a head width of 30-40% of the head length, the width of the head in P. amazonensis ranges from 51-69%, making it very easy to distinguish.

Pariosternarchus amazonensis is a member of an informal species-rich suprageneric taxon in the Apteronotinae known as the navajini.

The navajini are characterised by rhomboid scales (rather than ovoid ones) and anal fin pterygiophores that are longer (rather than shorter) than the length of the hemal spines.

The species lives on flooded beaches, deep river channels and in the mouths of tributaries of the Amazon. It is a relatively small apteronotid, with most specimens caught measuring 10-15cm/4-6" in length.

For more information see the paper: Albert JS and WGR Crampton (2006) - Pariosternarchus amazonensis: a new genus and species of Neotropical electric fish (Gymnotiformes: Apteronotidae) from the Amazon River. Ichthyological Exploration of Freshwaters, Vol. 17, No. 3, pp. 267-274.