Pachypops Gill 1861

Lilian Casatti, 2002, Taxonomy of the South American genus Pachypops Gill 1861 (Teleostei: Perciformes: Sciaenidae), with the description of a new species., Zootaxa 26, pp. 1-20 : 2-4

Genus Pachypops Gill 1861

Type species. Micropogon trifilis Mueller and Troschel 1848 : 622 (by original designation).

Diagnosis. Distinguished from the two other known South American freshwater sciaenid genera ( Pachyurus and Plagioscion ) by the following combination of characters: mouth inferior, presence of three mental barbels, the swimbladder with a pair log posterior branches projecting from shorter paired anterior appendages (Fig. 1), and presence of the expanded haemal spine on the first caudal vertebra (Fig. 2). Gender masculine.

Comments. According to Sasaki (1989), Pachypops is characterized phylogenetically by its swimbladder with a pair of anterior appendages (see Fig. 1), the possession of an unpored median barbel, and the possession of a pair of mental barbels. An unpublished phylogenetic study of South American freshwater sciaenids done by the author of the present paper reveals that the species of Pachypops share not only those synapomorphies listed by Sasaki (1989) but also an expanded haemal spine on the first caudal vertebra (see Fig. 2). These four synapomorphies are assumed to be homoplastic with other perciforms in the final most parsimonious phylogeny.

Jordan and Eigenmann (1889: 413) assigned Pachyurus adspersus Steindachner 1879 to the genus Pachypops . However, despite bearing three mental barbels and six mental pores, P. adspersus lacks the expanded haemal spine and the appendages on the swimbladder, which occur in Pachypops . Casatti (2001) considered P. adspersus a member of Pachyurus as originally proposed by Steindachner. An expanded haemal spine on the first caudal vertebra is also present in some other examined perciforms (the haemulid Haemulon steindachneri , the polynemid Polydactylus virginicus , and the sciaenids Dendrophysa russelli , Kathala axillaris , and Plagioscion auratus , pers. obser.) but it is interpreted as having been independently derived in these taxa.

Based on the barbel morphology Pachypops cevegei Cervigon 1982 is not a species of Pachypops , but instead a species of Micropogonias . Therefore, of six nominal species of Pachypops according to previous authors, two ( Pachypops adspersus and Pachypops cevegei ) are not assignable to the genus. The remaining nominal species are discussed below under “Comments” for Pachypops fourcroi and Pachypops trifilis .

Key to Species of Pachypops

1 Brown spots present on sides of body, body depth 4.3 or more in SL ............ ............................................. Pachypops pigmaeus n. sp. (Rio Machado and Madeira basins and upper Rio Branco, Brazil)

- Spots absent on sides of body, body depth less than 4.1 in SL ................ 2

2 Dark longitudinal stripes present on sides of body, horizontal eye diameter from 3.0 to 3.7 in HL ..... Pachypops trifilis (Rivers of Guyana and Rio Amazonas basin)

- Longitudinal stripes absent on sides of body, horizontal eye diameter from 2.4 to 3.1 into HL ............................................ Pachypops fourcroi (Amazonas, Essequibo, Corantijn, Approuague and Orinoco basins)