1Lecture 9• Origin of Actinopterygii (ray-finned fishes)• Late Silurian - Early Devonian - 400 mya• Monophyly of large assemblage > 23,000 species –we accept monophyly but interrelationships less well established.• Many confusing attempts to comprehend/classify lower Actinopterygian fishes • But - if only living members - relationships are, with few exceptions, reasonably well established. Actinopterygii2• Agassiz (1833-44) compendium fossil fish & Muller's (1845) classification living actinopterygians - 3 major assemblages: Chondrostei (sturgeon/paddlefish), Holostei (Gars/Amia), Teleostei• Basic divisions of Actinopterygian more-or-less accepted until phylogenetic systematics in late 1960's.• One of most influential publications -"Interrelationships of fishes” (1973) - Molded contemporary views of Actinopterygianinterrelationships by Greenwood, P. H., Miles, S., Patterson, C. eds, J. Linn. Soc. (London) 53 Supplement 1. Academic Press, New York, New York. Historical ContextLouis Agassiz• “I have devoted my whole life to the study of Nature, and yet a single sentence may express all that I have done. I have shown that there is a correspondence between the succession of Fishes in geological times and the different stages of their growth in the egg, -- that is all. It chanced to be a result that was found to apply to other groups and has led to other conclusions of a like nature.”Louis Agassiz, 18693• Problems associated with poorly preserved fossil taxa -Schaeffer's on Chondrostean interrelationships. Concluded many of old groups – “chondrostei" were paraphyletic but unable to do much more • Gardiner& Schaeffer reanalyzed major lower Actinopterygian – "Interrelationships of lower Actinopterygian fishes" 1989 Z. J. Linn. Soc. 97:135-187. • Mammoth work - array of fossils - previously grouped in various "chondrosteans and paleoniscids"• Basically see: Basal actinopterygians – (1) Cheirolepis(fossil Paleonisciformes), (2) Cladistia, (3) Chondrosteans=Acipenseriformes , (4) Neopterygians.1+2 = Most taxa represented are fossil –2 = polypterids living.3 = Chondrosteans – 2 living groups3a = Acipenseridae - sturgeons (25 recent species); Specialized bottom-feeders - bony scutes (retain three heavy layers- ganoine) - Heavily over fished. 3b = Polyodontidae - paddlefishes - two recent species. Polyodon spathula - Mississippi River and Psephurusgladius - Yangtze River, China. Highly modified planktivores.4Cheirolepis• Middle Devonian (398 to 385 mya) to Late Devonian (385 to 359 mya).• Phylogeny: Actinopterygians = (1) Cheirolepis (fossil Paleonisciformes), (2) Cladistia, (3) Chondrosteans, (4) Neopterygians.• Description: Possibly earliest actinopterygian with "standard" dermal skull bones; large orbit; long (~50 cm) body; broad-based pelvic fin; fins other than pelvic fin long; strongly heterocercal tail; fringing scales small or absent; minute scales with two ganoine(probably same as enamel) layers;BichirsCladistia – Polypterus(bichirs); Represented by 10 FW species - tropical Africa and one species -Erpetoichthyscalabaricus – reedfish. - Rope fish5• Highly aberrant Cladistia - numerous uniquely derived features – long, independent evolution:– Strange dorsal finlets– Series spiracular ossicles– Peculiar urohyal bone and parasphenoid• But retain # primitive Actinopterygian features = – heavy ganoid scales (external layer of ganoine)– gular plates– spiral valve in the intestine– lung-like swim bladder• Regardless of Cladistia, major problems in numerous fossil forms (will not go into).Sturgeons = Order Acipenseriformes• Family = Acipenseridae ~ 30 species • 5 rows bony plates on body• Caviar and ‘isinglass’ from swimbladder• Extremely threatened = dams, pollution, silt & overfishing6Paddlefish= Order Acipenseriformes• 2 living species = Polyodon spathula and Psephurus gladius• Elongate snouts = sensory (not dig) – eats zooplankton and phytoplankton• Extremely threatened = dams, pollution, silt & overfishing• D) Neopteryii - Current views - again vary -present that in Lauder and Liem (Gars, Amia and teleosts) • Three major groups: • 1) Ginglymodi - gars (Lepisosteidae – 2 genera and 7 spp.) • 2) Halecostomi - halecomorphi - several fossils, and amia (bowfin) – traditionally Holostei.• 3) Teleostei - subject of much of rest diversity survey – 20,000 + species.• Old group "holostei" is clearly broken up in this view and we have Amia and teleosts.7Gars = Order Lepisosteiformes• Gars - Order = Lepisosteiformes, Family = Lepisosteidae• 2 Family and 7 species (living) • Hard enameled scales of ganoin• Ambush predators Bowfin = Order Amiiformes• Bowfin - Family = Amiidae• 1 Living – Amia calva• Temperate eastern North America• Scales cycloid – dorsal fin entire length • Up to 40 inches and 8.5 lbs8ActinopterygiiNEXT - Evolution of particular function in Actinopterygian fishes in context of historical sequence of structural changes within clade• Function = feeding; specifically the elaboration of inertial suction feeding mechanisms. • Remember - aquatic medium (800 x dense and 80 x viscous than air). Also oxygen less, temperature stable, hydrate, buoyancy, viscosity (more drag). • Food acquisition on land = very different than water.9• Also - explore possible implications of very fundamental differences in aquatic versus terrestrial feeding modes - on trophic ecology of