Protosomes

Chordates

phylum chordata, animals at some point during their development have a notochord; a dorsal, hollow nerve cord, pharyngeal slits or clefts, and a muscular, post-anal tail

Notochord

a longitudinal, flexible rod that runs along the anterior-posterior axis of a chordate in the dorsal part of the body

Pharyngeal Slits (or Clefts)

in chordate embryos, one of the grooves that separate a series of pouches along the sides of the pharynx and may develop into a pharyngeal slit

Cyclostome

member of one of the two main clades or vertebrates; cyclostomes lack jaws and include lampreys and hagfishes

Gnathostomes

member of one of the two clades of vertebrates; gnathostomes have jaws and include sharks and rays, ray-finned fishes, coelacanths, lungfishes, amphibians, reptiles, and mammals

Chondrichthyan

member of the class Chondrichthyes, vertebrates with skeletons made mostly of cartilage, such as sharks and rays

Osteichthyans

member of a vertebrate clade with jaws and mostly bony skeletons

Ray-Finned Fish

member of the class Actinopterygii, aquatic osteichthyans with fins supported by long, flexible rays, including tuna, bass, and herring

Lobe-Fins

member of a clade of osteichthyans having rod-shaped muscular fins

Tetrapod

member of a vertebrate clade characterized by limbs with digits

Cuticle

a tough coat that covers the body; protects the animals and provides points of attachment for the muscles that moves the appendages

Amphibians

member of the tetrapod class Amphibia