WFB 232 Taxonomy, Week 3 7 Feb 2005
Superclass Gnathostomata Class Sarcopterygii (coelacanth & lungfishes) Lobe-finned fishes; gave rise to tetrapods Bony supports to tips of pectoral fins (similar to primitive human leg/arm) Lower Devonian (400 MYA)
Subclass Coelacanthimorpha Order Coelacanthiformes 1 living species, discovered in 1938 off of SE Africa Grow up to several hundred pounds, oviviparous, long-living
Subclass Porolepimorpha and Dipnoi (lungfishes) Found in Africa, South America Hang out in pools, if it dries up, make a cocoon of mud “lung” is a modified swim bladder – absorbs oxygen, removes wastes These fish can actually drown if held underwater too long!
Class Actinopterygii (ray-finned fishes) 50% of known fish species, major food source to humans Lateral line – specialized sensory organ to detect water movement and current Swim bladder
Subclass Chondrostei (bichirs, reedfish, sturgeons) Similar characterisitics to ancestors –heterocercal tail, spiracles Date at least as far back as Triassic/Jurassic (few fossils found)
Order Polypteriformes Family Polypteridae (bichirs & reedfish) Only a few living species (Africa) Unique dorsal fin – several small fins, lobate pectorals, supported by 2 bony elements Ganoid scales, lung-like air bladder Reedfish – no pelvic fins, ~ 90 cm long, “amphibious”
Order Acipenseriformes (Sturgeons) Cartilaginous endoskeleton, ganoid scales, spiracle, bony scutes along back Northern Hemisphere, found in fresh and saltwater Grow up to 9 meters long, live > 100 years,eggs are caviar Feed on invertebrates, small fishes In Vermont: Lake sturgeon (Acipenser fulvescens)
Subclass Neopterygii Lose the heterocercal tail & spiracles Only gars (Semionotiformes) have ganoid scales
Order Semionotiformes (gars) Family Lepisosteidae Elongate shape, ganoid scales, heavy bone material on head Found almost exclusively in freshwater, grow up to 3 meters long In Vermont: Longnose gar (Lepisosteus osseus)
Order Amiiformes (bowfin) Family Amiidae, Amia calva (only living species) Gular plate in mouth, young protection, divided gas bladder (aerial respiration) Tolerate very warm temps, poor water conditions Sexual dimorphism, eggs used as “fake caviar” Voracious predators – lots of sharp teeth in mouth; tough, sturdy body Triassic period Resident in Vermont.