Phylum Chordata

∞ generated and posted on 2016.11.05 ∞

Taxon of animals possessing a notochord during at least some period in their lives.

A notochord is a non-calcified endoskeleton, taking the place of the vertebral column, i.e., backbone. The notochord for most chordates is found only over the course of embryonic development.

Other features associated with all chordates, again at some point in their lives, are a dorsal hollow nerve cord (i.e., a spinal cord), a post-anal muscular tail, and what are known as pharyngeal slits (or pharyngeal clefts). The latter, in primitive chordates (i.e., members of subphylum Urochordata and subphylum Cephalochordata), are used as suspension-feeding devises.

Chordates also tend to possess segmentation known as somites, which are most obviously seen as the fleshy layers of fish bodies but also show up as the vertebrae making up backbones.

Note that not all chordates possess backbones, endoskeletons other than the notochord, or jaws, though in fact most do. The latter include nearly all fish and their terrestrial descendants.