BIO153H5 Lecture Notes - Lecture 18: Water Vascular System, Lancelet, Paraphyly
Document Summary
Deuterostomes includes ourselves and a number of invertebrate taxa. Deuterostomes are the only ones to include both vertebrates and invertebrates: invertebrates: echinoderms, vertebrates: chordates. Deuterostomes are phylogenetically diverse: protostomes do not have much distinction, unlike deuterostomes, whale and starfish are both deuterostomes. As the studies increased in magnitude, xeno are no longer considered protostomes or deuterostomes. This messes up the black and white classification. We have a very difficult time with things that appear to be both at the same time. The challenge is how to explain how evolution produced such a mixture. It seems like a protostome from an evolutionary perspective but it can also be a deuterostome. Cladogram: purple are all currently recognized echinoderms, hemichordate half a chordate, outside the chordate, xenoturbellida are out at the end because they were thought to be sister group of deuterostomes. Echinodermata: earliest divergent clade, the next major group is the chordate.
