An autonomic nervous system, as originally defined by Langley
(1898, 1921) is present in all vertebrates, although the anatomical
arrangement in cyclostomes (lampetroids and myxinoids) is not well
understood. Starting from the elasmobranchs (sharks, rays and
chimaeroids) and via teleosts (bony fish), amphibians and reptiles, it
is at least possible to construct an image of the increased complexity of
the autonomic system along the vertebrate lineage.