What are Deuterostomes?
Deuterostomes are a large superphylum of animals that includes chordates (vertebrates), echinoderms, hemichordates (acorn worms), and one small phyla, Xenoturbellida, which consists of two marine worm-like species. “Deuterostome” means “second mouth organism,” a reference to the fact that during embryological development in deuterostomes, the first body opening becomes the anus, and the second the mouth, unlike in protostomes, where it is the opposite. Another difference is in the cleavage of the embryo during growth — deuterostomes display indeterminate cleavage, where their is more room for variation in where cells ultimately end up, in contrast to the protostomes’ determinate cleavage, where the end position of every cell is fixed. The smaller superphylum relative to protostomes, deuterostomes have the benefit of containing the most complex animals. All animals above a certain arbitrarily-defined level of complexity are likely to be deuterostomes. For instance, arguably the most co
