Ancient Bony Fishes

Hypothesized Phylogenetic Relationships Ancient Bony Fishes Superclass Gnathostomata - jawed fishes Class Placodermi (plate-skinned) extinct Class Acanthodii (spiny sharks) Grade Teleostomi (“perfect mouth”) = Osteichthyes (“bony fishes”) • Class Sarcopterygii: “lobed fins” Class Chondrichthyes Class Sarcopterygii living • Class Actinopterygii: “ray fins” Class Actinopterygii Teleostomi (Osteichthyes) Characteristics of bony fishes • appeared 425 mya during the Silurian • jaws • probably evolved initially in freshwater • true bony skeleton (can be secondarily lost) • dominant by 380 mya • bony operculum covering gill arches • Ostracoderms had just died out • 3 semicircular canals, 3 otoliths • Acanthodians, placoderms, elasmobranchs were radiating at the same time – so origins of bony fishes unclear • paired fins • lungs or swimbladders (sometimes lost in benthic forms) • lepidotrichia replace ceratotrichia during ontogeny 1 Teleostomi (bony fishes) Sarcopterygii (lobed fins) Class Sarcopterygii (lobed fins) Subclass Coelacanthimorpha (coelacanths) Subclass Dipnoi (lungfish) Dipnomorphs Tetrapodamorphs (extinct - probably gave rise to tetrapods) Class Actinopterygii (ray fins) • appeared 400+ mya • marine and freshwater • lobed fins: series of bony elements link fins to pelvic and pectoral girdle (like tetrapods) • jaw suspension is autostylic (firmly attached to cranium) Subclass Cladistia Subclass Chondrostei Subclass Neopterygii Class Sarcopterygii (Sarcopterygians) = lobe-finned fishes Sarcopterygii (2 living spp.) Subclass Coelacanthimorpha (Actinistia) Order Coelacanthiformes Family Latimeridae 1. Coelacanthimorpha Coelacanth (“hollow spine”) • all fins lobed, except 1st dorsal • large swim bladder filled with fat 2. Dipnoi - lungfishes • bottom oriented predators, 100-250 meters • electrical senses • disappeared from fossil record 65 mya • Latimeria chalumnae found off South Africa in 1938 Coelacanth Latimeria chalumnae Pre-dating the dinosaurs by millions of years and once thought to have gone extinct with them, 65 million years ago, the Coelacanth with its missing link "proto legs" was discovered alive and well in 1938! Marjorie Courtenay-Latimer’s notes and sketch for J. L. B. Smith (1938) 2 Comoros Islands Chalumna River, South Africa Coelacanth footage #1 Coelacanth footage #2 The largest coelacanth ever captured Coelacanths are live-bearers viviparous oviparous ovoviviparous Maputo Museum photo of the Mozambique female before dissection. The fish was 178 cm in length and 98 kg. • live 40-50 yr • mature at 15 yr • 3 yr gestation! 3 Latimeria menadoensis Sarcopterygii Subclass Dipnoi (“double breath”) lung fish Order Ceratodontiformes (3 families) • evolved 400 mya, first in marine, moved to freshwater – all living representatives now FW • once an abundant group • functional lungs (evolved in stagnant waters?) BIG NEWS: 2nd species of coelacanth found off Indonesia in 1999! -- found and photographed in a fish market 3 families of lungfish • Australian (Ceratodontidae): heavy lobed fins, facultative air breather (1 species) • massive tooth plates - made excellent fossils - teeth are attached to interior bones, not jaw bones • estivation: state of reduced metabolism during dry-out • heart intermediate between fish and tetrapods • larvae have external gills in some spp. Australian lungfish: Ceratodontidae oldest living vertebrate? identical fossils from 140 million years ago • African (Protopteridae): fins reduced to filaments, obligate air breather with estivation (first classified as an amphibian) (4 species) • South American (Lepidosirenidae): fins reduced to filaments, obligate air breather (1 species) African lungfish: Protopteridae South American lungfish: Lepidosirenidae • juveniles have external gills – but are not amphibians! 4 Estivation Estivation Sarcopterygii Subclass Dipnoi Fin and Forelimb anatomy tetrapods Tetrapodamorpha Elpistostegalian: Tiktaalik roseae – the “missing link” between fishes and tetrapods Osteolepiform: similar to early tetrapod ancestor Osteolepiform Amphibian (ancient) lungfish Next group: “Traditional” phylogeny Tree favored by molecular data Class Actinopterygii (“ray fins”) see Fig. 11.23 for details Arnason et al. 2004 5 Gnathostomata Class Actinopterygii (“ray fins”) Subclass Cladistia Order Polypteriformes (bichirs) Class Actinopterygii • first appeared 425 mya • dominant freshwater fishes about 340 mya • began to invade salt water about 340 mya Subclass Chondrostei (“cartilage bone”) Order Acipenseriformes (sturgeons & paddlefish) Subclass Neopterygii (“new fins”) Order Lepisosteiformes (gars) Order Amiiformes (bowfin) Division Teleostei (modern bony fish) Branchiostegal rays Characters of Class Actinopterygii -- many and diverse and changing Most Actinopterygii have: • fins attached to body via fin rays • branchiostegal rays • distinct pelvic and pectoral girdles • bony skeleton Pectoral girdle pelvic Pelvic girdle Class Actinopterygii (“ray fin”) • Subclass Cladistia Order Polypteriformes (bichirs) • Subclass Chondrostei Order Acipenseriformes (sturgeons & paddlefish) Order Palaeonisciformes - extinct • Subclass Neopterygii Order Lepisosteiformes Order Amiiformes Division Teleostei (modern bony fish; w/ 40 orders!) Subclass Cladistia, Order Polypteriformes (sometimes placed in order Brachiopterygii) • ancient group & unclear what other group they are mostly closely related to • probably sister group to all other Actinopterygians Characters: • dorsal fin with 5-18 finlets • lobed pectoral fins • lungs • skeleton partly cartilaginous • spiral valve intestine • heavy ganoid scales • spiracles (exhale air through them) • no brachiostegals 6 Order Polypteriformes Family Polypteridae: bichirs (“bih-shears”) Bichirs (& reedfishes) -- note the finlets • 10 spp., all freshwater, Africa • larvae with external gills Subclass Chondrostei Order: Palaeonisciformes (extinct) • first appeared about 425 mya • order Palaeonisciformes gave rise to the Neopterygii Characters of modern chondrosteans: • cartilaginous skeleton (secondarily derived) • heterocercal tail • spiral valve intestine • heavy ganoid scales • spiracles • one brachiostegal • fin rays • changes in jaw bones and musculature • lighter, more flexible scales • Devonian (about 400 mya) Order: Acipenseriformes white sturgeon (Acipenser transmontanus) Families: Acipenseridae (sturgeons, 25 spp.) freshwater/anadromous Polyodontidae (paddlefishes, 2 spp.) freshwater • big: paddlefish up to 5-m long & sturgeons up to 8.5 m and 1300 kg! • North America & Eurasia • live in temperate & arctic rivers (long upstream migrations -- up to 2500 km) • live up to 150 years of age! • largest freshwater fish in North America • 6.1 m (20 feet)! • 800 kg (1800 pounds)! 7 Family Acipenseridae: sturgeons Caviar from sturgeon • 4 barbels (for taste & feel) • 5 rows of scutes for armor • elongated snout • protrusible mouth • single dorsal fin many species are currently endangered because of caviar harvest & dams Prone to overfishing • long lived (100+ yr) • late maturity (up to 30 yr) • females may spawn only every 3-5 yr or longer Family Polyodontidae: paddlefishes • no bony scutes (virtually naked) • midwater (not benthic) • paddle-like snout • planktivores • 1 sp. in North America, 1 in China Valuable! female beluga sturgeon: (captured in Russia, 1924) • 1,227 kg (2,700 lb.) • yielded 245 kg (540 lb.) of caviar • if eggs qualified as grade OOO Malossol caviar, which sells on the internet for as much as $165/oz ($5,808/ kg)… • the fish would be worth nearly $1,423,000!! • electroreception organs (ampullary organs) on paddle Subclass Neopterygii • first appeared about 345 mya • radiated 290-190 mya, and most extensively 80-65 mya Shared characters of modern neopterygians (intermediate between chondrosteans and teleosts) Lepisosteiformes (gars) & Amiiformes (bowfin): • heterocercal tail • spiral valve intestine • ossified skeleton • functional lungs / gas bladder Otherwise very different from each other 8 Lepisosteiformes: gars (7 spp.) (AKA Ginglymodii) • evolved about 200 mya Ganoid (Chondrostei, Lepisosteiformes) Characters • large swimbladder also used as lung • ganoid scales • spiral valve intestine • toxic eggs (laid on aquatic plants) • North America, Central America, and Cuba • ambush predators, primarily freshwater Alligator gar Ctenoid (Teleostei) Cycloid (Teleostei, Amiiformes) Alligator gar 8’ 2”, 245 lb. ?? impale prey on teeth rather than suction feed Amiiformes, family Amiidae (bowfin) -- single species, Amia calva • • • • • • once abundant group coexisted w/ dinosaurs North America large lung spiral valve intestine cycloid scales more closely related to Teleostei than gar Male gular plate “Gar-Like” Traits “Teleost-Like” Traits • abbreviated heterocercal tail • cycloid scales • vascularized swimbladder • amphicoelous vertebrae • spiral-valve intenstine • suction feeders • parental care 9 Evolution of protrusible jaws: Chondrostean → Evolution of paired fin location in teleosts Neopterygian/Teleost (primitive) Division Teleostei (perfect bone) • >95% living species = 400+ families • arose 200 mya • common genera of today existed 40-70 MYA • evolved from several lines • 4 subdivisions Primitive teleosts - Next Lecture 10