|
Palaeonisciformes
The Palaeonisciformes, commonly known as "palaeoniscoids" (also spelled "paleoniscoid", or alternatively "paleoniscids") are an extinct grouping of primitive ray-finned fish (Actinopterygii), spanning from the Silurian/Devonian to the Cretaceous. They are generally considered paraphyletic, but their exact relationships to living ray-finned fish are uncertain. While some and perhaps most palaeoniscoids likely belong to the stem-group of Actinopteryii, it has been suggested that some may belong to the crown group, with some of these possibly related to Cladistia (containing bichirs) and/or Chondrostei (which contains sturgeons and paddlefish). Many palaeoniscoids share a conservative body shape and a similar arrangement of skull bones, though paleoniscoids as a whole exhibit considerable diversity in body shape. Historic background The systematics of fossil and extant fishes has puzzled ichthyologists since the time of Louis Agassiz, who first grouped all Palaeozoic ray-finned f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palaeoniscum
''Palaeoniscum'' (from , 'ancient' and 'cod-fish' or 'woodlouse') is an extinct genus of ray-finned fish from the Guadalupian, Middle to Lopingian, Late Permian period (Guadalupian-Lopingian) of England, Germany, Turkey, North America and Greenland, and possibly other regions. The genus was named ''Palaeoniscum'' in 1818 by Henri Marie Ducrotay de Blainville, but was later misspelled as ''Palaeoniscus'' by Blainville and other authors (notably Louis Agassiz). ''Palaeoniscum'' belongs to the family (taxonomy), family Palaeoniscidae. The type species ''Palaeoniscum freieslebeni'' was named after Johann Carl Freiesleben (1774–1846), mining commissioner of Saxony. ''P. freieslebeni'' is the most common taxon in the Wuchiapingian aged Kupferschiefer and Marl Slate, where it constitutes 80% of all fish fossils. The genus is considered to be a poorly defined wastebasket taxon. ''Palaeoniscum'' had a torpedo-shaped body in length, with a deeply forked caudal fin and tall dorsal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
