Part 5: Arthropods, Echinoderms & Others

Arthropoda (Cambrian–Recent)

• Exoskeleton of chitin, sometimes calcified.

• Major fossil groups: Trilobites, Eurypterids, Ostracods, Barnacles, Crustaceans, Insects

Echinodermata (Ediacaran–Recent)

• Calcitic skeleton, water vascular system, five-fold symmetry.

• Groups: Crinoids, Blastoids, Starfish, Brittle stars, Sea urchins, Sea cucumbers

Graptolites (Cambrian–Pennsylvanian)

• Colonial suspension feeders with collagen skeletons.

• Important index fossils of the Paleozoic

Conodonts (Cambrian–Triassic)

• Tooth-like calcium phosphate elements from early craniates.

• Exceptionally useful index fossils

Craniata (Vertebrates, Cambrian–Recent)

• Primitive forms had bone exoskeleton + cartilage endoskeleton.

• Modern vertebrates ossify internal skeleton