Class Chondrichthyes

Description

Class Chondrichthyes belongs to Phylum Chordata, which are characterized of having a hollow nerve chord or notochord at one point in their life. Chordates are so diverse that they are separated into 3 sub-phylums: Urochordata, Cephalachordata, and Vertebrata. Sub-Phylum Vertebrata is the most notable because they contain animals with a back bone. Under this sub-phylum, there are seven classes one of which is Chondrichthyes. The word Chondrichthyes derives from modern Latin. Chond meaning "cartilage" and ichthyes meaning "fish".

Physical Features

The most defining characteristic of Chondrichthyes is their cartilaginous skeleton. They also share a number of similarities such as coloration, pectoral fins located on their sides, placoid scales, gill arches, and eyes on the side of their head. They have bilateral symmetry and have adapted denticles on their skin to aid in protection. They have a lighter belly to camouflage with the light from above and a darker upper portion of their body to blend in with the depths of the ocean. Chondrichthyes must continue swimming to keep oxygenated water flowing through their gills. They have a closed circulatory system, along with a two-chambered heart. They have a closed digestive system and a very sensitive nervous system. Their noses are especially sensitive. They fertilized internally and often give birth to live young but, some develop from eggs. Unfortunately, there is no parental care after the young are born. The class is separated into two subclasses in which characteristic differ.