Ischnacanthus gracilis - A Devonian Fish
Ischnacanthus gracilis was a fish species that lived during the Devonian period (416-359 million years ago). It is classified as being in the class Acanthodii and the order Ischnacanthiformes. Fossils of Ischnacanthus gracilis have been found in Scotland.
Ischnacanthiformes were fish that had spindle-shaped bodies that were covered by small mosaic scales. They had small teeth which were mostly in the lower jaw..Some species had no teeth. They first appeared in the late Silurian and lasted until the mass extinction that occurred at the end of the Permian (about 251 million years ago). Fossils of these fish have been found in both saltwater and freshwater deposits.
The class Acanthodii originated in the Ordovician. The Ischnacanthiformes and other Acanthodians have this point in common: Their fins (except for the caudal) were supported by large spines made of dentine.
Neal Robbins
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