Lecture 5 - Early Fishes Three distinct classes arose from the ancestors of bony fishes • Acanthodians • Sarcopterygians • Actinopterygians Lecture 5 - Early Fishes Actinopterygii (aka ray-finned fishes) • Cladistia • Chondrostei • Neopterygii • Lepisostei • Amiformes • Teleostei • Osteoglossomorpha • Elopomorpha • Ostarioclupeomorpha • Euteleostei Lecture 5 Early Fishes Class Subclass Division Subdivision Actinopterygii Cladistia Chondrostei Neopterygii Lepisosteiformes Amiformes Teleostei Osteoglossomorpha Elopomorpha Ostarioclupeomorpha Euteleostei Actinopterygii Ray-finned fishes • Sister taxon of the Sarcopterygians • First known from scales in the late Silurian (~420 mybp) • 3 subclasses: Cladistia, Chondrostei, Neopterygii • Previously, with Acanthodians & Sarcopterygians, formed Teleostomi Teleostomi • Teleostomi is paraphyletic… • Relationships in the early evolution of fishes are still unresolved • Splits between Chondrichthyes, Osteichthyans, & Ancanthodians ~500 mybp • occurred quickly • there are many hypotheses… Actinopterygii Ray-finned fishes • Sister taxon of the Sarcopterygians • First known from scales in the late Silurian (~420 mybp) • 3 subclasses: Cladistia, Chondrostei, Neopterygii • Previously with Acanthodians & Sarcopterygians formed Teleostomi • Scales ganoid, cycloid, or ctenoid Subclass Cladistia Order Polypteriformes (Bichirs & Reedfish) Subclass Cladistia Order Polypteriformes (Bichirs & Reedfish) • 11 spp. bichirs and one reedfish • sister group to all other Actinopterygians • ganoid scales • enamel like ganoin on surface • obligate air breathers Subclass Cladistia Order Polypteriformes (Bichirs & Reedfish) Erpetoichthys calabaricus Cladistia Distribution • limited to west and central tropical Africa including Congo and Nile rivers • 95 mybp • unique pectoral fins… Subclass Chondrostei (sturgeons and paddlefishes) • taxonomic classification is very insecure • many extinct orders • w/ derived characteristics • only one extant order • Acipenseriformes Acipenseriformes Mostly cartilaginous Intestine with spiral valve Fin rays more numerous than their basal supports Two extant familes • Acipenseridae • Polyodontidae Acipenseridae – (sturgeons) • restricted to northern hemisphere – 26 spp. • mostly cartilaginous barbels protusible mouth • extremely long lived • spawn in freshwater • bony scutes Acipenseridae – (sturgeons) Beluga Huso huso 8.6m & 1300kg - 118 years old $5000/kg 1227 kg female had 245 kg of caviar Polyodontidae – (paddlefish(es?)) Polyodontidae – (paddlefish) Psephurus gladius Chinese paddlefish …likely extinct I hope the caviar was amazing… Subclass Neopterygii The “new fins” in town! Fin rays equal in numbers to their supports in dorsal and anal fins Pterygiophores Lepisosteiformes – (gars) • N. & Central America -7 spp. • spiral valve • air breathers • ganoid scales Lepisosteiformes – (gars) Alligator gar Atractosteus spatula Up to 3m Amiiformes – (bowfin) • sole survivor • air breather • males guard young • sister to Teleost Amia calva Amiiformes – (bowfin) • “cycloid” scale • no ganoine layer, just particles • analogous to teleost • spiral valve Division Teleostei – “perfect bones” Division Teleostei 96% of all extant fishes 27 anatomical synapomorphies, no molecular ones - stiffen tail • Most important are modifications to the skull & caudal skeleton Four major radiations Division Teleostei 96% of all extant fishes 27 anatomical synapomorphies, no molecular ones • Most important are modifications to the skull & caudal skeleton Four major radiations • Osteoglossomorpha • Elopomorpha • Otocephala • Euteleostei Subdivision Osteoglossomorpha - most primitive living teleost - well developed teeth on tongue Two orders: Hiodontiformes (Mooneye, Goldeye) Osteoglossiformes Osteoglossiformes African butterflyfish Knifefish - most speciose family in subdivision >200 spp. Mormyrid elephantfishes Pirarucu Osteoglossiformes Arapaima gigas obligate air breathers Osteoglossiformes • males brood young in Arowana mouth 4-6 weeks • facultative air breathers Subdivision Elopomorpha Leptocephalus larvae Leptocephalus larvae Development of Leptocephalus larva Elopiformes tarpons Anguilliformes Eels and Morays Albuliformes bonefishes Freshwater eel migration (anguilllidae) Anguilla rostrata - catadromous Subdivision - Ostarioclupeomorpha Superorder Clupeomorpha + Superorder Ostariophysi • Mostly molecular synapomorphies • Anatomical synapomorphies involve inner ear and swimbladder Superorder Clupeomorpha Anterior extension of the swimbladder enters the skull • can detect low frequency sounds (e.g. tail beats) Clupeiformes • almost all are pelagic schooling fish herring anchovies Superorder Ostariophysi Represent 74% of all freshwater species Synapomorphies: Schrekstoff: fright substance hormone • given off when specialized dermal cells rupture Schrekreaction: alarm response It has been secondarily lost in some fishes Superorder Ostariophysi Ostar = small bone, physa = a bladder Weberian apparatus: a unique series of bones that connect the gas bladder with the inner ear Superorder Ostariophysi divided into two series: Series Anotophysi Series Otophysi Gonorynchiformes Cypriniformes (milkfishes) Characiformes Siluriformes Gymnotiformes Superorder Ostariophysi divided into two series: Series Anotophysi Series Otophysi Gonorynchiformes Cypriniformes (milkfishes) Characiformes Siluriformes Gymnotiformes Lack Weberian Synapomorhpy: apparatus Weberian • more primitive apparatus taxon piranha 10,222 spp. ~74% of freshwater fishes Weberian apparatus catfish Cypriniformes 4,239 spp. – 599 in last 10 yrs Characiformes 2,087 spp. – 305 in last 10 yrs Siluriformes 3,681 spp. – 615 in last 10 yrs Gymnotiformes 215 spp. – 77 in last 10 yrs • most advanced Ostariophysans • continuous, low electrical output • except in electrical eel.