The resultant coelom is termed an enterocoelom. These buds, known as coelomic pouches, fuse to form the coelomic cavity, as they eventually separate from the endodermal layer. The endodermal lining of the archenteron (or the primitive gut) forms membrane protrusions that bud off and become the mesodermal layer.

In deuterostomes, internal pockets of the endodermal lining called the archenteron fuse to form the coelom.

There are a series of other developmental characteristics that differ between protostomes and deuterostomes, including the mode of formation of the coelom and the early cell division of the embryo. The word deuterostome comes from the Greek word meaning “mouth second,” indicating that the anus is the first to develop. Recall that protostome and deuterostomes differ in certain aspects of their embryonic development, and they are named based on which opening of the digestive cavity develops first.

The phyla Echinodermata and Chordata (the phylum in which humans are placed) both belong to the superphylum Deuterostomia. Describe the distinguishing characteristics of chordates.Describe the distinguishing characteristics of echinoderms.By the end of this section, you will be able to:

Does a tarfish have spiny kin