Chimpanzees and humans might be considered to be members of the same family in a Linnaean hierarchy. Humans share more derived characters with chimpanzees than with any other living animal. Chimpanzees are the direct ancestors of humans. Chimpanzees share a relatively recent ancestor with humans. All of the animal phyla can be unambiguously labeled as deuterostomes or protostomes solely on the basis of their pattern of embryonic development.
Pseudocoelomate animals lack a fluid-filled body cavity other than the gut.
In coelomate animals, the coelom is completely lined with tissue derived from embryonic mesoderm. Class Reptilia Class Agnatha Class Placodermi Class Chondrichthyes 27. One animal phylum we did not discuss in class is Phylum Hemichordata, which includes the acorn worms often found living in burrows along coastlines. This phylum is often grouped with the Echinodermata and the Chordata. These animals are classified as a single species.