400 likes | 573 Views
5 th edition text. ~24,000 species. Tetrapods. Teleosts. lobe-fin fishes. ray-fin fishes. ray-fin fish lobe-fin fish extinct lobe-fin fish extinct early tetrapod. fin rays digits. ”early actinopterygians”. lobe-fins. ray-fins. bichirs and reedfishes freshwater (150 MYA). North
E N D
5th edition text ~24,000 species Tetrapods Teleosts lobe-fin fishes ray-fin fishes
ray-fin fish lobe-fin fish extinct lobe-fin fish extinct early tetrapod fin rays digits
”early actinopterygians” lobe-fins ray-fins
bichirs and reedfishes freshwater (150 MYA) North America Eurasia Australia Africa South America cladogram for major continents
Polypteriformes ~16 sp 2 genera aka ropefish similar to bichir larval stage
skeleton: cartilage, bone scales: ganoid fins: “lobed”
gular plates lobed fins
bichirs Polypterus sp. spiracles (~elasmobranchs) spiral valve intestine ventral lungs and gills
Sarcopterygii Actinopterygii African Australian African bichir South American lungs gills always external larval gills
reedfish Erpetoichthys calabaricus external gills as adult neoteny?
“early actinopterygians” lobe-fins ray-fins
gars also Central America North America Eurasia Present day ~400 MYA Australia Africa South America cladogram for major continents
NEAq spotted gar Lepisosteus oculatus longnose gar Lepisosteus osseus
Lepisosteiformes ~7 sp. FW bone skeleton interlocking vertebrae (~reptiles, load-bearing) extended body and snout
anterior nostrils numerous teeth
spiral valve intestine diamond-shaped ganoid scales (native american arrowheads)
scales PLACOID GANOID ELASMOID enamel/dentine ganoine/bone enamel/bone
African Australian African bichir South American lungs gills certain stages always American gar always • buoyancy • respiration external larval gills dorsal lung
heart gars: up to 72 valves
oviparity toxic eggs? adhesive disk larval stage
distribution Great lakes to Gulf of Mexico
longnose gar Lepisosteus osseus 50 lbs, 2 m spotted gar Lepisosteus oculatus 6 lbs >1 m East: introduced NEAq
Atractosteus spatulaalligator gar MCZ specimen ~3 m length
‘lie-in-wait’ or ‘ambush’ predators double-breasted cormorant with gar
gar pike-characin pike or pickerel needflefish pike killifish barracuda pike-head Example: convergent evolution distant relatives converge
Example: divergent evolution close relatives diverge
Early Actinopterygii sturgeon bowfin gar
sturgeon and paddlefish gars bowfin North America Eurasia Present day ~400 MYA Australia Africa South America cladogram for major continents
laurentian distribution sturgeon and paddlefishes NA, Asia gars NA, CA bowfin NA
Early Osteichthyes Tetrapods Teleosts lobe-fin fishes ray-fin fishes