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ARRATIA, Gloria:Basal teleosts and teleostean phylogeny1997. [in English] – 168 pp., 108 figures, 9 tables, 3 appendices. ISBN 978-3-931516-14-7 Euro 50.00 series: Palaeo Ichthyologica |
Complete descriptions, as preservation permits, are provided for new Jurassic taxa (e.g., Cavenderichthys talbragarensis n.gen. from Australia, Elops-like species and leptocephalous larvae, Leptolepides haerteisi n.sp., Orthogonikleithrus hoelli n.sp. and Tischlingerichthys viohli n.gen. et sp. from Germany); redescriptions of some South American Oxfordian teleosts (e.g., Chongichthys dentatus) and re-evaluation of the composition of the Jurassic family Varasichthyidae and the phylogenetic position of the Late Jurassic genera Ascalabos, Tharsis, Leptolepides and the Cretaceous genus Erichalcis are given.
The relationships among Jurassic teleosts from Europe, Middle America, South America and Australia, the ?Early Cretaceous osteoglossomorph Lycoptera, the Early Cretaceous ostariophysan Gordichthys and clupeomorph Santanaclupea, the Cretaceous and Tertiary clupeomorph Diplomystus, the Cretaceous "salmoniforms" Erichalcis and Humbertia and the extant Elops, Hiodon, Chanos, Denticeps, Engraulis, Esox, Umbra, Oncorhynchus and Thymallus are evaluated based on 135 unweighted morphological characters by using cladistic principles.
One tree (length 420; CI = 0.414) is the result of the analysis. The following monophyletic groups are recognized: the †Varasichthyidae (with †Domeykos + [†Varasichthys + [†Protoclupea + †Luisichthys]]), the †Ichthyodectiformes (sensu PATTERSON & ROSEN 1977, but including the Jurassic Pachythrissops propterus), the elopomorphs (including the Jurassic Anaethalion and Elops-like species), the osteoglossomorphs, the clupeomorphs, the ostariophysans (including the Jurassic Tischlingerichthys n.gen.), and a clade "salmoniforms" which comprise two subgroups: [†Humbertia + [†Erichalcis + [†Orthogonikleithridae n. fam.]]] and the extant esocoids plus salmonids. The †Orthogonikleithridae is a monophyletic group composed of the Jurassic genera Orthogonikleithrus and Leptolepides. There is no support for the monophyly of the family †Leptolepidae sensu NYBELIN (1974).
The new phylogenetic hypothesis based on both, fossil and Recent teleosts, shows that †Leptolepis coryphaenoides is more primitive than members of the †Varasichthyidae; the †Ichthyodectiformes are more advanced than †Ascalabos, †Tharsis and †Cavenderichthys n.gen. The †Ichthyodectiformes are the plesiomorphic sister group of the elopomorphs plus the osteoglossomorphs and more advanced teleosts. The osteoglossomorphs are the sister group of two main clades: one composed by the clupeomorphs and the ostariophysans and another by the "salmoniforms".
The addition of new basal teleosts (e.g., the "salmoniform" †Orthogonikleithrus) as well as new characters and new interpretations of certain characters changes previous hypotheses of relationships of teleosts. The addition of fossil forms increases the amount of detected homoplasies for characters of Recent groups. The inclusion of basal teleosts in an analysis of interrelationships changes the polarity of characters; consequently, the fossil basal teleosts influence the sister group relationships of extant groups. The new hypothesis of relationships of teleosts presented here shows that most teleostean lineages are supported mainly or only by homoplastic characters.
Following the new phylogenetic hypothesis new taxa, the supercohorts Elopomorpha and Osteoglossocephala, and the subcohort Ostarioclupeomorpha, as well as new usage for other higher taxa, the cohort Clupeocephala and subcohort Euteleostei, are proposed. As pointed out above, most of these taxa are defined at the primitive level by few uniquely derived characters and several homoplasies which reflect the problem that teleostean phylogeny faces when both fossil and Recent evidence are considered in phylogenetic analyses.
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