The first jawed fish were the:a.
placoderms.
b. acanthodians.
c. ostracoderms.
d. chrondrichthyes.
e. agnatha.
Question 2The mass extinction at the end of the Ordovician set the stage for:a.
more species to go extinct.
b. groups of organisms to diversify.
c. groups of organisms to withdraw from previous habitats.
d. groups of organisms to repopulate abandoned niches.
e. groups of organisms to diversify AND to repopulate abandoned niches.