2C. Articulates.
Annelida.
Crustacea.
Tracheata.
2D. Echinoderms.
Monorchonia.
Pentorchonia.
2E. Tunicates.
Copelata.
Ascidiae.
Thalidiae.
2F. Vertebrates.
2F.1. Acrania-Lancelet (Without Skull).
2F.2. Craniota (With Skull).
2F.2A. Cyclostomes. ("Round-Mouthed").