1. VERTEBRAL COLUMN and BRAINCASE Ostracoderms2. GNATHOSTOMES (Jaws) Placoderms Sharks, Rays: Chondrichthyians Ray-finned Fishes: Actinopterygians Coelacanths, Lungfishes3. TETRAPODS (Four Limbs) Always the same structure: one bone, two bones, many bones (“One too many”): femur or humerus; tibia/fibula or radius/ulna; wrist/fingers or ankle/toes Temnospondyls, Lepospondyls4. AMNIOTES (Watertight Egg)5. SAUROPSIDS (A pair of openings in the palate [roof of mouth]) Turtles, Pareiasaurs, Procolophonids6. DIAPSIDS (Sauropsids) (A pair of openings behind the eyes for jaw muscle attachments) Plesiosaurs, Lizards, Ichthyosaurs7. ARCHOSAURS (A pair of openings between eye and nose: antorbital opening) Crocodylians, Pterosaurs, Dinosaurs (including birds)
(Early) HETEROSTRACANS: https://en.wikipedia.org/wiki/HeterostraciALSO SEE: http://tolweb.org/Heterostraci/16904/1997.01.01(Late) CEPHALASIPIDS: https://en.wikipedia.org/wiki/Cephalaspidomorphi
Cephalaspidomorphs are a group of jawless fishes named for Cephalaspis of the osteostracans. Most biologists regard this taxon as extinct, but the name is sometimes used in the classification of lampreys, because lampreys were once thought to be related to cephalaspids. If lampreys are included, they would extend the known range of the group from the Silurian and Devonian periods to the present day.
1. https://en.wikipedia.org/wiki/Lamprey2. https://www.britannica.com/animal/lamprey3. http://www.bbc.com/earth/story/20151102-meet-a-lamprey-your-ancestors-looked-just-like-it
CEPHALASPIS: https://www.britannica.com/animal/CephalaspisPTERASPIS: http://www.prehistoric-wildlife.com/species/p/pteraspis.htmlPHLEBOLEPIS: https://en.wikipedia.org/wiki/Phlebolepis