Cybium, Revue Internationale d’Ichtyologie
Copyright © 2002 Société Française d’Ichtyologie

(1) Antenne IRD, Laboratoire d’Ichtyologie, Muséum national d’Histoire naturelle, 43 rue Cuvier, 75231, Paris cedex 05, FRANCE.
(2) Laboratorio de Ictiologia, INPA-CPBA, Cx.P. 478, 69011-970 Manaus, AM., BRÉSIL.
(3) CSP, Laboratoire d’Ichtyologie, Muséum national d’Histoire naturelle, 43 rue Cuvier, 75231, Paris cedex 05, FRANCE.
(4) INRA, Laboratoire SCRIBE-INRA, Campus de Beaulieu, 35042, Rennes cedex, FRANCE.

Résumé. - Tometes trilobatus est une espèce différente de Myleus setiger. Tometes est un genre proche de Mylesinus, Ossubtus et du sous-genre Myleus (Myleus) avec lesquels il partage plusieurs caractères uniques chez les Serrasalminae. Les os des mâchoires sont laminaires et les séries de dents du prémaxillaire sont étroitement accolées les unes aux autres. Le mésethmoïde est large, peu épais et les ailes latérales sont très réduites. La fenêtre olfactive est large. En avant des nageoires pelviennes, les serrae, peu nombreuses et réduites à des épines, ne dessinent pas de carène abdominale. Mylesinus, Ossubtus et Tometes ont des dents incisiformes engrenées bi- et tricuspides. Tometes diffère de ces deux genres par les dents des mâchoires qui sont plus épaisses et plus courtes. Les deux dernières dents du prémaxillaire de Tometes sont différentes des premières, courtes et à couronne sigmoïde. Chez Mylesinus et Ossubtus, toutes les dents de la série labiale du prémaxillaire sont hautes, planes avec une couronne rectiligne.

Abstract. - Supplementary description and rehabilitation of Tometes trilobatus Valenciennes, 1850, type-species of Tometes Valenciennes (Characidae: Serrasalminae).

Tometes trilobatus, type-species of Tometes, was placed in synonymy with Myleus setiger since its description in 1850. Tometes was thus considered by authors as synonym of Myleus. Recently, we could show that Myleus setiger, type-species of Myleus, was different from Tometes trilobatus. The examination of the specimens collected in French Guiana and in the State of Amapa in Brazil, associated with a study of the types of Tometes enables us to show that Tometes is different from Myleus and shares several characters with Mylesinus and Ossubtus. After a short historical background of various works referring to Tometes trilobatus, we give a detailed redescription of the morpho-anatomical and meristical characteristics of the species, and we rehabilitate the Tometes genus.
Tometes trilobatus is different from Myleus setiger and T. unilobatus is synonym of T. trilobatus. Tometes is a genus close to Mylesinus, Ossubtus and Myleus (Myleus) sub-genus with which it shares several unique characters in the Serrasalminae. The bones of the jaws are laminar and the series of teeth of the premaxillary are placed side by side. The mesethmoïde is broad, not very thick and the supraethmoïdal wings are very reduced. The olfactive foramen is broad. The prepelvic serrae are few and reduced to spines, and do not draw an abdominal keel. Mylesinus, Ossubtus and Tometes have geared bi- and tricuspid incisiform teeth. Tometes differs from this two genus by thicker and lower teeth. The posteriormost premaxillary labial teeth of Tometes are different of the anterior ones, short and with a sigmoïd crown. All the labial premaxillary teeth of Mylesinus and Ossubtus are plane with a right crown.
Tometes trilobatus seems to be associated with the Podostemaceae, the rupestral plants characteristic of the rapids of the studied area. By taking the intestine of some specimens for the study of the parasites, we observed Podostemaceae in abundance in the stomachs. Tometes, Mylesinus and Ossubtus present a diet closely related to Podostemaceae, associated with a parasitic hyperinfestation, while Myleus (Myleus), Myleus (Myloplus), Myleus (Paramyloplus) and Myleus (Prosomyleus) present a diet less specialised and composed of exogenic sheets, fruits or seeds and invertebrates.
The typology of the localities of collection of T. trilobatus confirms that it is a rheophilic species. In the three basins considered (Oyapock, Flexal and Araguari), the captures always took place in the high courses and more particularly in the zones of rapids.

Key words. - Tometes - Tometes trilobatus - Tometes unilobatus - Myleus setiger - External morphology - Skeleton anatomy - Synonymy - Rehabilitation - Serrasalminae - Characidae.