Uniting Traits

Phylum Chordata (chordates) includes fish, frogs, birds, snakes, humans etc. This very diverse phylum is untied by four traits:
1. Notochord
2. Dorsal hollow nerve cord
3. Pharyngeal gill slits
4. Post anal tail
Many of these traits are only present in the embryo stage of life. The notochord is a long flexible support rod replaced by a back bone in humans. The dorsal hollow nerve cord (DHNC) runs along the dorsal surface just above the notochord. The front end of the DHNC developes into a brain. The pharayngeal gill slits are paired strucures in the pharyngeal or throat region. In terrestrial vertebrates, gill slits are only present during the embryonic stage. Last but not least, the post anal tail, is found in the larval or embryonic stages of invertebrate chordates.