A new species of Placidichthys (Halecomorphi: Ionoscopiformes) from the Lower Cretaceous Marizal Formation, northeastern Brazil, with a review of the biogeographical distribution of the Ophiopsidae
Paulo M. Brito, Jesús Alvarado-Ortega, 2008. "A new species of Placidichthys (Halecomorphi: Ionoscopiformes) from the Lower Cretaceous Marizal Formation, northeastern Brazil, with a review of the biogeographical distribution of the Ophiopsidae", Fishes and the Break-up of Pangaea, L. Cavin, A. Longbottom, M. Richter
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A new halecomorph fish is described from the Early Cretaceous Marizal Formation of Tucano Basin. This new material is identified as a new species of Placidichthys, P. tucanensis sp. nov. based on the absence of an anal fin, the lower number of flank scales in the caudal region, the slender shape of the body, and body proportions. Placidichthys tucanensis sp. nov. increases the distribution and diversity of ophiopsids in the western part of the Tethys Sea, being distributed along the epicontinental seas of Gondwana.
Placidichthys is considered the sister-taxon of the exclusively Cretaceous taxa Teoichthys+Macrepistius from the western Tethys. These groups show a discernible geographical distribution pattern with Placidichthys known only from the Southern margin of the Tethys region (South America), whilst Teoichthys and Macrepistius are known only from North America and possibly Europe.
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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.