Cladoselache is a genus of extinct shark that first appeared in the Devonian period. Cladoselache was characterized by broad-based paired fins, a short stout bony spine preceding the first of the two dorsal fins, and a large lunate tail-fin. Often cited as among the best known, earliest, and/or most primitive of the early chondrichthyans (cartilaginous fishes including modern chimaeroids, sharks and rays), Cladoselache now appears ill defined and poorly diagnosed. Most of the best fossil specimens of Cladoselache are from the Upper Devonian Cleveland Shales, and include complete individuals of around 1 m (3.3 ft) in length. Several of these have mineralized traces of soft tissues, including much of the superficial jaw and gill musculature, and even apparent traces of internal organs such a