Chapter 18 – Turtles

Anyone can identify a turtle based on the uniquely evolved carapace and plastron. In addition, all turtles share a unique cranial architecture including dentary bones that lack teeth but have keratinous sheaths as cutting edges. Turtles are comprised of 327 species distributed among 14 families. Their distribution is nearly global and includes widespread species that are marine. Turtles occur in swamps, rivers, streams, on land, and in the oceans. Conservation status of turtles is summarized. An up-to-date phylogeny details approximate time periods during which divergences occurred during the evolutionary history of turtles and shows evolutionary relationships among the families as we now know them. Taxonomic accounts provide information on generic content, distribution, characteristics, and biology of each family.