ARRATIA,, G.; Museum fuer Naturkunde, 10115 Berlin, Germany. gloria.arratia@rz.hu-berlin.de: Origin and Early Radiation of Teleostei

The Telesotei and its sister-group the Halecomorphi are currently included in the Division Halecostomi. During the last 30 years, fundamental work concerning the monophyly of the Teleostei, as well as of the Halecomorphi, and the phylogenetic relationships among halecostome subgroups has been generated. Although there is apparently no doubt concerning the monophyly of both the Halecomorphi and Teleostei, new investigations on Triassic and Jurassic ‘pholidophoriforms’ raise important questions concerning (1) the monophyly of these groups, (2) the evolutionary significance of certain features, (3) the age of the Teleostei versus that of the stem-groups, and (4) the content of the halecostome subgroups. For instance, the three characters (e.g. symplectic articulating with lower jaw; one supramaxilla) currently accepted as supporting the monophyly of Halecomorphi turn into homoplasies because they are present in some of the Triassic pholidophorid genera and in stem-group teleosts. The monophyly of the Teleostei stands only on one uniquely derived morphological character (quadrate with long posteroventral process), and all other characters previously proposed in the literature as uniquely derived become homoplastic. The study of Triassic pholidophorids, at the base of the Teleostei in the cladogram, reveals that ‘true’ teleosts are much older than most of the taxa that have been suggested as stem-group teleosts; thus, the group arose probably in the Middle-Early Triassic (~240 m.y. ago). Although by the Late Triassic the teleosts were represented by several genera, it was in the Jurassic, particularly the Late Jurassic (~151 m.y. ago), when most of the stem and some of the modern teleostean lineages (e.g. elopiforms) arose. In contrast, the osteoglossomorphs do not appear in the record until about 137 m.y. ago.