Chordates are believed to have evolved from Deuterostomes, a superphylum which consists of vertebrates. The main characteristic of Deuterostomes is their embryological development, where the blastosphere develops into the anus, and the mouth is developed at the opposite end. The digestive tract than forms in between the anus and the mouth, connecting both to each other. The earliest fossil record of Deuterostomes, the Kimberella, an organism similar to a jellyfish, is believed to have appeared over 558 million years ago, or during the Precambrian eon. Scientists continue to debate whether the Kimberella should be classified as a type of jellyfish or a …show more content…
Urochordates are tunicate-like creatures which filter feed and remain sessile and form large colonies. These organisms showed the early signs of a dorsal nerve chord with the notochord, which connected one end of the body to the other. Cephalochordates are lancelet-like organisms which, much like Urochordates, are filter feeders. These organisms lacked brains, well-structured heads, and sense organs, and retained most traits from Deuterostomes. Vertebrates, which are classified by their well-structured skulls, a spinal column rather than a notochord, and vertebrae. One subdivision of Vertebrates are the Craniates, hagfish-like organisms that possess well-structured skulls, but lack