The unifying characteristic of chordates (Chordata) is the presense of a notochord (an internal skeletal rod that provides support) during some stage of the animal's development. Although the majority of chordates are vertebrates (animals whose notochord is replaced during development with interlocking vertebrae), there are also two groups of chordates that are invertebrates.
Chordates also exhibit the following characteristics:
- bilateral symmetry
- body segmentation
- endoskeleton (bony or cartilaginous)
- pharyngeal pouches (present during some stage of development)
- complete digestive system
- ventral heart
- closed blood system
- tail (at some stage of development)
Animals > Chordates
Chordates are divided into the three basic subgroups, Tunicates, Lancelets and Vertebrates.