CHARACTERISTICS: animals with a backbone; have small, rootless teeth on jaws and roof of mouth that are replaced throughout life; usually produce gelatinous egg mass, called “spawn”
KNOWN SPECIES: approximately 5,000
SIZE RANGE: less than .40 inch to about 5 feet (1 centimeter to about 160 centimeters)
WHERE THEY LIVE: in most freshwater and land environments, usually close to water; highest diversity is in tropics