Chondrichthyans are gnathostomes (= jawed fishes), and, as such, share a number of characters with other jawed vertebrates (i.e. bony fishes, amphibians, reptiles and mammals). These include jaws and paired appendages with internal skeletal support (in the form of pelvic and pectoral fins). Chondrichthyans are also the first vertebrates to possess true teeth. Throughout the evolutionary history of chondrichthyans, these characters have undergone a great deal of independent adaptive change. This has greatly complicated attempts to resolve the relationships of chondichthyan groups, as many specimens exhibit bizarre combinations of advanced and primitive characters (i.e. advanced tooth structure with primitive fins).
There are two broadly accepted synapomorphies (i.e. characters unique to a group) that define chondrichthyes as a monophyletic clade. These are
Author: Andrew Gillis
Last updated: 15 November 2004
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