Vertebrates include many of the animals with which we are familiar. Fish, amphibians, reptiles, birds and mammals are vertebrates. But the vertebrates, as a group, comprise just one group in a larger, more inclusive group, the chordates. This is less familiar, as those chordates that are not vertebrates are not found every day. Invertebrate chordates include the urochordates, or tunicates, colloquially the sea-squirts, marine creatures that generally (but not always) spend their adult lives fixed in one place, as sponges and corals do; and the cephalochordates or lancelets — translucent, vaguely fishlike creatures which although in principle fully mobile throughout life, spend much of the time half-buried in the sand in inshore waters.
KeywordsNeural Crest Monophyletic Group Nerve Cord Ciliated Band Gill Slit
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