Superclass Gnathostomata Class Sarcopterygii

Taxonomy, Week 3 7 Feb 2005

Lobe-finned fishes; gave rise to tetrapods

Bony supports to tips of pectoral fins (similar to primitive human leg/arm)

Lower Devonian (400 MYA)

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

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”

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)

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)

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