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Classification of Fishes: Key Groups and Characteristics
- 1. Classification of Fishes Tuhar Mukherjee
- 2. • Systematic Position: Super class: Gnathostomata • Mouth protected by jaws • Three semicircular canals • Paired limbs usually present • Brachial skeleton represented by separate gill arch • Centra of vertebra usually present Series: Pisces • Gills present • Paired limbs but not pentadactyl • Median fins supported by special skeleton • Aquatic Fishes are aquatic ectothermic vertebrates having pharyngeal gills for respiration, paired and unaired fins with fin rays for propelling and balancing in aquatic media
- 3. • Peter Artedi (1705-1735) Father of Ichthyology • Important schemes of classification: Berg 1940, Romer 1962, Greenwood et al 1966, Young 1981, Romer and Parsons 1986, Nelson 1994
- 4. Series Pisces Pterichthys Coccostei Acanthodii Elasmobranchii Xenacanthii Cladoselachii Selachii Holocephali Dipnoi Teleostomi Crossopterygii Actinopterygii Berg 1940
- 5. Subclass Class Grade Superclass Gnathostomata Placodermiomorphi Placodermi Chondrichthiomorphi Chondrichthyes Teleostomi Acanthodii Sarcopterygii Coelacanthimophi Rhizodontimorpha Osteolepimorpha Tetrapodes Unnmaned Porolepimorpha and Dipnoi Actinopterygii
- 6. Pterichthyes • Head and thorax with strong body plates • Tail heterocercal • Pelvic find usually absent • Mouth ventral • Devonian Period • Pterichthyes
- 7. Coccostei • Strong cranial roof formed by the union of bony plates • Bony plates sculptured by presence of tubercles • Posterior part of body prolonged into whip like tail • Operculum covering branchial arches • Pectoral fins greatly reduced, represented by a pair of small unmovable lobed structure • Well formed dorsal fin Also called joint necked fishes Upper Silurian to Upper Devonian period Acanthaspis
- 8. Acanthodii • Elongated fusiform body • Eyes large • Mouth placed terminally • Tail heterocercal • Series of paired fins present between the pectoral and pelvic fins Also called Needle fined sharks Upper Silurian to Devonian Mesacanthus
- 9. Holocephali • Hyostylic jaw suspension: Palatoquadrate is fused with neurocranium (Indicates the name ‘Holos’ whole and ‘cephalos’ head) • Diphycercal caudal fin • Male with claspers Chimeras (Chimaera monstrosa) Elephant fish (Callorhynchus antarcticus)
- 10. Elasmobranchii • Body covered by dermal placoid scales and mucous glands • Pelvic fins covered by claspers • Tail heterocercal • Operculum absent • Kidney opisthonephros • Jaw suspension hyostylic • Ampullae of Lorenzini a sensitive electroreceptor present on the head • Trimethylamine oxide (TMAO) helps in osmoregulation Jurassic to recent Scoliodon
- 11. Xenacanthii • Body slender with dorsal fin • Epichordal and hypochordal rays are equally developed • Paired fins paddle like and of Archipterygium pattern (Long axis with pre- and post-axial rays) • Jaw suspension amphistylic Lower carboniferous to Lower Permian Xenacanthus
- 12. Cladoselachii • Body elongated with terminal mouth • Jaw suspension amphistylic • Teeth cladodont • Male without claspers Cladoselache
- 13. Selachii • Elongate fusiform bodies • Male with claspers • Jaw suspension amphistylic and hyostylic Sharks and Rays
- 14. Dipnoi • Also called lung fish • Autostylic jaw suspension (palatoquadrate fused to undivided cranium) • Air bladder serves as lungs Lepidosiren, Neoceratodus, Protopterus
- 15. Teleostomi • Body covered with dermal (cycloid, ctenoid or ganoid scales) • Tail homocercal • Bony operculum • Vertebrae amphicoelous • Hyostylic jaw suspension
- 16. Crossopterygii • Lobe fin fish • Scale covered with cosmine layer • Caudal fin heterocercal, diphycercal or hetero- diphycercal • Autostylic jaw suspension Latimeria chalumnae, L. menadoensis
- 17. Actinopterygii • Ray-finned fish • Radials of pair fins not arranged biserially • Scale not cosmoid type • Internal nostrils and spiracles absent Labeo rohita,