Taxonomy and Classification of Fish

Topics: Fish, Shark, Vertebrate Pages: 16 (3574 words) Published: April 27, 2013
Station 1. Fish Diversity

Classification of the Major Taxa of Fish
! Phylum Chordata ! Subphylum Vertebrata ! Supraclass Agnatha ! Order Osteostraci ! Order Anaspida ! Order Heterostraci ! Order Coelolepida ! Order Cyclostomata ! Class Myxinoidea ! Class Petromyzontida ! Class Placodermi ! Order Arthrodiriformes ! Order Antiarchiformes ! Supraclass Gnathostomata ! Class Chondrichthyes ! Subclass Elasmobranchii ! Order Cladoselachiformes ! Order Xenacanthiformes ! Order Selachii ! Order Batoidea ! Subclass Holocephali ! Order Chimaeriformes ! Class Acanthodii ! Class Osteichthyes ! Subclass Actinopterygii ! Infraclass Chondrostei ! Infraclass Holostei ! Infraclass Teleostei ! Subclass Sarcopterygii ! Order Crossopterygii ! Order Dipnoi examples jawless fishes

hagfish lampreys

jawed fishes

extinct Paleozoic sharks Paleozoic freshwater sharks typical sharks skates and rays chimaeras or ratfishes various extinct fishes higher bony fishes ray-finned fishes sturgeon, paddlefish; primitive ray-finned fishes gars, bowfins; dominant ray-finned fishes of Mesozoic most bony fish; dominant in Cenozoic and recent times lobe-finned fishes ancestors of land vertebrates lungfishes

Station 1. Fish Diversity

includes the living forms LAMPREYS and HAGFISHES, and several extinct forms The jawless fish (supraclass Agnatha; a = without, gnathos = jaws) include the extinct ostracoderms and the living lamprey eels and hagfishes. Ostracoderms, the earliest known fossil chordates, have been found in the rocks of the Ordovician, Silurian and Devonian periods, These jawless fish were small, armored, bottom-dwelling freshwater filter feeders. The head was covered with thick bony plates, and the trunk and tail were covered with thick scales. Ostracoderms had median fins; some species had paired pectoral fins. The living relatives of the Ostracoderms are the lampreys and hagfishes. These animals have cylindrical bodies up to a meter long supported by a cartilaginous skeleton. Their smooth skin lacks scales, and they have neither jaws nor paired fins. Most hagfish eat worms and other invertebrates, which they burrow for or prey on dead and disabled fish.



Station 1. Fish Diversity

Relevant features:
anadromous and freshwater; cool zones of world European river lamprey, Lampetra fluviatilis one or two dorsal fins are present eyes well developed dorsal and ventral nerve roots separated sucking mouth; barbels absent; rasping teeth on oral disc and tongue small cerebellum sexes separate disc! eggs small, not yolky, occurring in the thousands; larval stage mouth ! teeth! opening! undergoes radical metamorphosis in fresh water •! die shortly after spawning •! parasitic (freshwater or anadromous) or non-parasitic (only freshwater) •! •! •! •! •! •! •! •! olfactory! pineal eye! organ! brain! nostril! dorsal! nerve ! aorta! chord! digestive! notochord! pharynx! gonad!

horny ! teeth! sucking ! mouth! rasping ! aortic ! tongue! arches!

tongue! infra-oral! tooth plate!

breathing! pericardial! atrium! intestine! coelom! pharynx! cartilage! liver! ventral! gill ! ventricle! peritoneum! aorta! slit!

Lamprey structure

Oral disc and teeth of lamprey

Station 1. Fish Diversity

Relevant features:
•! •! •! •! •! •! •! •! •! •! •! •! •! •! marine; temperate zones of the world no cerebellum eyes are degenerate, lens absent barbels present around biting mouth teeth only on tongue plus one on palate the dorsal fin is absent; the caudal fin extends onto part of the dorsal surface dorsal and ventral nerve roots united numerous mucus pores along body expel a slimy substance (hence nickname “slime eels”), for feeding and defense can go through knotting movements to free themselves from entanglement and own slime ovaries and testes in same individual, but only one functional (not hermaphrodite) eggs large, yolky, up to 30...
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