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CRANIATE

CRANIATES

Fish have not always existed in the fossil record, nor have modern fish existed since the first appearance of fossil fish. Craniates share modifications of the skeletal system (cartilaginous components of the skull), nervous system (including mixed spinal nerves, shared brain regions, an autonomic nervous system, a vestibulocochlear nerve, a semicircular canal in the ear, most of the basic tastes, and many shared neural pathways), the cardiovascular system (layers of the heart, heart chambers, heart valves, prothrombin, and shared homologous blood vessels), immune system (homologs of the thymus, spleen and antibody-like molecules), digestive system (extensions of the serosa, the gall bladder, and the pancreas), urinary system (nephrons), and other modifications including thyroid follicles, an endocrine pancreas, POMC genes, cells homologous to the adrenal cortex, eye muscles, and hypobranchial musculature.

HAGFISH

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