Can the comparative study of the morphology and histology of the scales of Latimeria menadoensis and L. chalumnae (Sarcopterygii: Actinistia, Coelacanthidae) bring new insight on the taxonomy and the biogeography of recent coelacanthids?
François J. Meunier, Mark V. Erdmann, Yves Fermon, Roy L. Caldwell, 2008. "Can the comparative study of the morphology and histology of the scales of Latimeria menadoensis and L. chalumnae (Sarcopterygii: Actinistia, Coelacanthidae) bring new insight on the taxonomy and the biogeography of recent coelacanthids?", Fishes and the Break-up of Pangaea, L. Cavin, A. Longbottom, M. Richter
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SEM (Scanning electron microscopy) and photonic microscopy (ground sections) studies confirm that the scales of the coelacanth Latimeria menadoensis have strong morphological and histological similarities with the scales of L. chalumnae. They are both elasmoid scales, the external layer of which is made of radial ridges that are overlaid, on the posterior field, by odontodes. The odontodes of L. menadoensis are made of the typical mineralized tissues described for teeth of the coelacanth and their width is similar to that of L. chalumnae odontodes. Globular corpuscles are found in the isopedine contact with the external layer. Their mineralization seems to be inotropic as in the Mandl’s corpuscles of teleost elasmoid scales. Scale organisation in L. menadoensis does not show any characteristics that may support significantly, in the absence of additional evidence, two different species in the extant coelacanths.
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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.