Elasmobranchs are a Subclass Chondrichthyes that are Classified as Carilaginous Fish

2146 WordsJan 25, 20189 Pages
PART I The Elasmobranchs are a subclass of class Chondrichthyes. The Chondrichthyes are classified as the Cartilaginous fishes. Aside from the Elasmobranchs, this class has another subclass named Holocephali which is comprised of the chimaera. The Elasmobranchs are comprised of sharks (Selachii) and the rays and the similarly structured skates (Batoidea) Van-Eyl, S. M., Siebeck, U. E., Champ, C. M., Marshal, J., & Hart, N. S. (2011). There have been fossils of sharks found dating about 400 million years and while there is much data that points to diversification throughout the millennia, skates and rays only appear about 200-100 million years ago (Wilga 2005). The Elasmobranchs are classified apart from other fishes despite their external similarities due to several key structural differences. One of these is the absence of a swim bladder. True fishes use this gas filled organ to control their buoyancy without having to waste physical energy on maintaining the desired depth in water. Instead, the Elasmobranchs have developed especially large livers that can produce and withhold large amounts of oil. This is especially evident in the sharks where the liver can sometimes weigh up to 20 percent of their total body weight. Further characteristics that define the Elasmobranch subclass include placoid scales or dermal denticles. These are homologous to true scales in function but are closer in structure to teeth (hence their name). The scales are comprised of a pulp cavity

    More about Elasmobranchs are a Subclass Chondrichthyes that are Classified as Carilaginous Fish

      Open Document