2) cephalochordate. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.
...Any of various primitive chordate animals of the subphylum Cephalochordata, such as the lancet, that lack a true vertebral column. Of, relating to, or belonging to...

3) trilobite. The Columbia Encyclopedia, Sixth Edition. 2001
...trilobite, (tri´lbit´) (KEY) , subphylum of the phylum Arthropoda that includes a large group of extinct marine animals that were abundant in the Paleozoic era. They...

4) crustacean. The Columbia Encyclopedia, Sixth Edition. 2001
...crustacean, (krusta´shn) (KEY) , primarily aquatic arthropod of the subphylum Crustacea. Most of the 44,000 crustacean species are marine, but there are many freshwater...

5) tunicate. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.
...Any of various chordate marine animals of the subphylum Tunicata or Urochordata having a cylindrical or globular body enclosed in a tough outer covering and including...

6) lancelet. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.
...Any of various small, flattened marine organisms of the subphylum Cephalochordata, structurally similar to the vertebrates but having a notochord rather than a true...

7) urochordate. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.
...A chordate marine animal of the subphylum Urochordata; a tunicate. Having a urochord....

8) vertebrate. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.
...or spinal column. 2. Of or characteristic of vertebrates or a vertebrate. A member of the subphylum Vertebrata, a primary division of the phylum Chordata that includes...

9) jawless fish. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.
...marine and freshwater fishes lacking a jaw and paired appendages that constitute the subphylum Agnatha. The only present-day jawless fish are the hagfish and lampreys....

10) Chordata. The Columbia Encyclopedia, Sixth Edition. 2001
...of the body-wall musculature, containing no internal organs. In vertebrates-animals of the subphylum Vertebrata-a backbone of bone or cartilage segments called vertebrae...