Some of these animals have gas bladders, and these vertebrates include chondrichthyes [kon-DRIK-thees] and osteichthyes [oh-STIK-thees].
This group of vertebrates included placodermi, whose heads and necks were covered by bones. Currently considered to consist of several classes, some of these vertebrates contain photophores that emit light. This group includes the agnatha, which is jawless. Some of these animals have gas bladders, and these vertebrates include chondrichthyes [kon-DRIK-thees] and osteichthyes [oh-STIK-thees]. Name these vertebrates that do not have limbs with digits and which include lampreys, rays, sharks, and guppies.
This group of vertebrates included placodermi, whose heads and necks were covered by bones.
fish