Birth of the modern world: The Tertiary
The Osteoglossomorpha are a clade of primitive teleostean fishes with modern representatives in five biogeogeographic regions and fossil representatives on six continents. The centre of modern diversity is in Africa but the centre of fossil diversity is in E Asia. Key fossil taxa include: †Phareodus, †Joffrichthys, and †Ostariostoma in N America; †Lycoptera, †Paralycoptera, and †Huashia among others in E Asia; †Brychaetus and possibly †Thaumaturus in Europe; †Palaeonotopterus, †Singida, and †Chauliopareion in Africa; †Tavernichthys in India; and †Musperia in SE Asia.
Morphological phylogenies to date have disagreed on three main points: the relationships of †Lycoptera, of Pantodon, and of Notopterids and Mormyrids. Molecular phylogenies have similarly differed on the last two points. In this study a combined set of morphological data was generated from previous studies, including data from three recently described or redescribed taxa (the African †Singida and †Chauliopareion and the Chinese †Xixiaichthys) and maximum parsimony was used to generate a revised hypothesis of relationships. Our analysis recovered †Lycoptera, †Paralycoptera+ †Tanolepis, and †Xixiaichthys as stem-group osteoglossomorphs, †Singida as sister to Pantodon within Osteoglossidae, †Chauliopareion as a stem osteoglossid, †Ostariostoma as a stem osteoglossiform, and Notopteridae as sister to Mormyroidea and †Palaeonotopterus.
These results do not lend themselves to easy explanations of osteoglossomorph biogeography involving either dispersal from a centre of origin or vicariant division of a widely distributed ancestor. Recent suggestions of an ancient (Palaeozoic) origin for osteoglossomorphs are flawed. The evidence, instead, is consistent with an origin within the Mesozoic and the biogeographic explanation involves extensive extinction of clades from continents where they occurred in the past.
Figures & Tables
This volume, in honour of Peter L. Forey, is about fishes as palaeobiogeographic indicators in the Mesozoic and Cenozoic. The last 250 million years in the history of Earth have witnessed the break-up of Pangaea, affecting the biogeography of organisms. Fishes occupy almost all freshwater and marine environments, making them a good tool to assess palaeogeographic models.
The volume begins with studies of Triassic chondrichthyans and lungfishes, with reflections on Triassic palaeogeography. Phylogeny and distribution of Late Jurassic neoselachians and basal teleosts are broached, and are followed by five papers about the Cretaceous, dealing with SE Asian sharks, South American ray-finned fishes and coelacanths, European characiforms, and global fish palaeogeography. Then six papers cover Tertiary subjects, such as bony tongues, eels, cypriniforms and coelacanths.
There is generally a good fit between fish phylogenies and the evolution of the palaeogeographical pattern, although a few discrepancies question details of current palaeogeographic models and/or some aspects of fish phylogeny.