Editing Chondrichthyes (section)

===Appendages===
Apart from [[electric ray]]s, which have a thick and flabby body, with soft, loose skin, chondrichthyans have tough skin covered with dermal teeth (again, Holocephali is an exception, as the teeth are lost in adults, only kept on the clasping organ seen on the caudal ventral surface of the male), also called [[placoid scale]]s (or ''dermal denticles''), making it feel like sandpaper. In most species, all dermal denticles are oriented in one direction, making the skin feel very smooth if rubbed in one direction and very rough if rubbed in the other.

Originally, the pectoral and pelvic girdles, which do not contain any dermal elements, did not connect. In later forms, each pair of fins became ventrally connected in the middle when scapulocoracoid and puboischiadic bars evolved. In [[Batoidea|rays]], the pectoral fins are connected to the head and are very flexible.

One of the primary characteristics present in most sharks is the heterocercal tail, which aids in locomotion.<ref>{{cite journal |first1=C. D. |last1=Wilga |first2=G. V. |last2=Lauder |title=Function of the heterocercal tail in sharks: quantitative wake dynamics during steady horizontal swimming and vertical maneuvering |journal=[[Journal of Experimental Biology]] |volume=205 |issue=16 |pages=2365–2374 |year=2002 |doi=10.1242/jeb.205.16.2365 |url=http://jeb.biologists.org/content/205/16/2365.short |pmid=12124362}}</ref>