Prehistoric fish 2011320 211840447 2008-05-12T10:17:43Z 87.194.204.195 reverted previous edits [[Image:Cretaceous Period Fish by dyet.jpg|thumb|200px|Fish fossil from Cretaceous period]] '''Prehistoric fish''' are various groups of [[fish]]es that lived before recorded [[history]]. A few, such as the [[coelacanth]] still exist today and are considered [[living fossil]]s. The first fish and indeed the first [[vertebrate]]s, were the [[ostracoderms]], which appeared in the [[Cambrian]] Period, about 510 million years ago, and became [[extinct]] at the end of the [[Devonian]], about 350 million years ago. Ostracoderms were jawless fishes found mainly in fresh water. They were covered with a bony [[armor]] or scales and were often less than 30 cm (1 ft) long. The ostracoderms are placed in the class [[Agnatha]] along with the living jawless fishes, the [[lamprey]]s and [[hagfish]]es, which are believed to be descended from the ostracoderms. The first fish with jaws, the acanthodians, or spiny [[shark]]s, appeared in the late [[Silurian]], about 410 million years ago, and became extinct before the end of the [[Permian]], about 250 million years ago. Acanthodians were generally small sharklike fishes varying from toothless filter-feeders to toothed [[predator]]s. They were once often classified as an order of the class [[Placodermi]], another group of primitive fishes, but recent authorities tend to place the acanthodiaes or that both groups share a common [[ancestor]]. The [[placoderm]]s, another group of jawed fishes, appeared at the beginning of the [[Devonian]], about 395 million years ago, and became extinct at the end of the [[Devonian]] or the beginning of the [[Mississippian]] ([[Carboniferous]]), about 345 million years ago. Detailed anatomical studies of fossil remains by the Swedish scientist [[Erik Stensiö]] strongly suggest that the placoderms were closely related to sharks. Placoderms were typically small, flattened bottom-dwellers, however, many, particularly the arthrodires, were active midwater predators. ''[[Dunkleosteus]]'' was the largest and most famous of these. The upper jaw was firmly fused to the skull, but there was a hinge joint between the skull and the bony plating of the trunk region. This allowed the upper part of the head to be thrown back, and in arthrodires, this allowed them to take larger bites. The cartilaginous-skeleton [[shark]]s and [[Batoidea|rays]], class [[Chondrichthyes]], which appeared about 370 million years ago in the middle [[Devonian]], are generally believed to be descended from the bony-skeleton placoderms. The cartilaginous skeletons are considered to be a later development. The modern bony fishes, class [[Osteichthyes]], appeared in the late [[Silurian]] or early [[Devonian]], about 395 million years ago. The early forms were freshwater fishes, for no fossil remains of modern bony fishes have been found in marine deposits older than [[Triassic]] time, about 230 million years ago. The Osteichthyes may have arisen from the acanthodians. A subclass of the Osteichthyes, the ray-finned fishes (subclass [[Actinopterygii]]), became and have remained the dominant group of fishes throughout the world. It was not the ray-finned fishes, however, that led to the evolution of the land vertebrates. The ancestors of the land vertebrates are found among another group of bony fishes called the [[Choanichthyes]] or [[Sarcopterygii]]. [[Choanate fish]]es are characterized by internal nostrils, fleshy fins called lobe fins, and cosmoid scales. The choanate fishes appeared in the late [[Silurian]] or early [[Devonian]], more than 390 million years ago, and possibly arose from the acanthodians. The choanate fishes include a group known as the [[Crossopterygii]], which has one living representative, the [[coelacanth]] ([[Latimeria]]). During the [[Devonian]] Period some crossopterygian fishes of the order (or suborder) [[Rhipidistia]] crawled out of the water to become the first [[tetrapods]]. The story of vertebrate evolution started in the seas of the [[Cambrian]] period, when jawless, toothless, soft-bodied fishlike creatures wriggled through the water, sucking up microscopic food particles. Only after tough, non-decaying bone was developed (initially as a scaly outer covering and later within the body) did [[fossil]]s form and become preserved in the rocks. And only then could [[paleontologist]]s take up the story with any certainty. The earliest traces of bony scales are found in rocks of the Late [[Cambrian]] period, and the first recognizable vertebrate fish has been found in [[Australia]]n rocks of Early [[Ordovician]] age. So, the first chapter in the vertebrate evolution starts with the ancient ''[[Arandaspis]]'', a fish about 6in/15cm long with no jaws, no teeth and no fins other than a tail. It did, however, have gills and a stiffening rod of cartilaginous material (the [[notochord]]) that served as a backbone. Groups of various prehistoric fishes include: [[Image:Fishapods.jpg|thumb|right|350px|Late [[Devonian]] [[vertebrate]] speciation saw [[Sarcopterygii|lobe-finned fish]] like ''[[Panderichthys]]'' having descendants such as ''[[Eusthenopteron]]'' which could breathe air in muddy shallows, then ''[[Tiktaalik]]'' whose limb-like fins could take it onto land, preceding the first tetrapods such as [[Acanthostega]] whose feet had eight digits, and ''[[Ichthyostega]]'' with developed limbs, negotiating weed-filled swamps. Lobe-finned fish evolved into [[Coelacanth]] species which survive to this day.]] ===Jawless fish=== *''[[Arandaspis]]'' *''[[Astraspis]]'' *''[[Boreaspis]]'' *''[[Dartmuthia]]'' *''[[Doryaspis]]'' *''[[Drepanaspis]]'' *''[[Errivaspis]]'' *''[[Haikouichthys]]'' *''[[Hemicyclaspis]]'' *''[[Jamoytius]]'' *''[[Myllokunmingia]]'' *''[[Pikaia]]'' *''[[Pharyngolepis]]'' *''[[Promissum]]'' *''[[Pteraspis]]'' *''[[Thelodus]]'' *''[[Tremataspis]]'' ===Cartilaginous fish=== *''[[Cladoselache]]'' *''[[Cobelodus]]'' *''[[Deltoptychius]]'' *''[[Heliobatis]]'' *''[[Hybodus]]'' *''[[Ischyodus]]'' *''[[Scapanorhynchus]]'' *''[[Sclerorhynchus]]'' *''[[Spathobathis]]'' *''[[Stethacanthus]]'' *''[[Tristychius]]'' *''[[Xenacanthus]]'' ===[[List of acanthodians|Acanthodians]]=== ===Sharks and placoderms=== <!-- Isn't this grouping a bit far-fetched? --> *''[[Bothriolepis]]'' *''[[Cladoselache]]'' *''[[Coccosteus]]'' *''[[Ctenurella]]'' *''[[Dunkleosteus]]'' *''[[Gemuendina]]'' *''[[Groenlandaspis]]'' *[[Megalodon]] or [[Megatooth shark]] *''[[Ostracoderm]]'' *''[[Palaeospondylus]]'' *''[[Pterichthyodes]]'' *''[[Squalicorax]]'' *''[[Otodus obliquus]]'' ===Primitive ray-finned fish=== *''[[Aspidorhynchus]]'' *''[[Canobius]]'' *''[[Cheirolepis]]'' *''[[Dapedium]]'' *''[[Lepidotes]]'' *''[[Moythomasia]]'' *''[[Palaeoniscum]]'' *''[[Perleidus]]'' *''[[Platysomus]]'' *''[[Pycnodus]]'' *''[[Saurichthys]]'' *''[[Semionotus]]'' ===Modern ray-finned fish=== *''[[Berycopsis]]'' *''[[Enchodus]]'' *''[[Eobothus]]'' *''[[Gryouchus]]'' *''[[Gyrosteus]]'' *''[[Hypsidoris]]'' *''[[Hypsocormus]]'' *''[[Knightia]]'' *''[[Leptolepis]]'' *''[[Pholidophorus]]'' *''[[Protobrama]]'' *''[[Sphenocephalus]]'' *''[[Thrissops]]'' === Fleshy-lobed fish === * ''[[Chinlia]]'' * ''[[Dipnorhynchus]]'' * ''[[Dipterus]]'' * ''[[Eusthenopteron]]'' * ''[[Griphognathus]]'' * ''[[Gyroptychius]]'' * ''[[Holoptychius]]'' * ''[[Macropoma]]'' * ''[[Osteolepsis]]'' * ''[[Strunius]]'' == See also == * [[Prehistoric life]] == References == {{Citations|date=February 2008}}<!-- Do not remove this notice until all facts in the article are cited properly. --> * Janvier, Philippe. '''Early Vertebrates''' Oxford, New York: Oxford University Press, 1998. ISBN 0-19-854047-7 * Long, John A. '''The Rise of Fishes: 500 Million Years of Evolution''' Baltimore: The Johns Hopkins University Press, 1996. ISBN 0-8018-5438-5 [[Category:Prehistoric fish| ]] [[Category:Paleontology]] [[fr:poisson préhistorique]] [[pt:Peixes pré-históricos]]