Also located on the dorsal side of the skate are their two eyes which allow for predator awareness. Skate's gill slits are located ventrally as well, but dorsal spiracles allow the skate to be partially buried in floor sediment and still complete respiratory exchange. Their mouths are located on the underside of the body, with a jaw suspension common to Batoids known as euhyostyly. Placoid scales have a pointed tip that is oriented caudally and are homologous to teeth.
SKAT DEFINITION SKIN
A large portion of the skate's dorsal body is covered by rough skin made of placoid scales. Skates are cartilaginous fishes like other Chondrichthyes, however, skates, like rays and other Rajiformes, have a flat body shape with flat pectoral fins that extend the length of their body. Description General Batoidea characteristics There are at least 45 dubious species of skates worldwide. However, there is little information about the diets of about 24% of these species. There are 13 genera and about 245 valid species. The Rajidae are considered monophyletic because of their similarity in appearance. Five scientists take credit for the rapid increase of findings. Since 1950, 126 new species of skates have been discovered. Skates have more valid species (574) than any other group of cartilaginous fishes.
There are 17 genera recognized in the family Rajidae: The number of species is likely to increase as taxonomic issues are resolved and new species are identified. Skates are the most diverse elasmobranch group, comprising over 20% of the known species. Chondrichthyes is divided into two subclasses of which Elasmobranchii includes skates, rays, and sharks. This class consists of all the cartilaginous fishes, including sharks and stingrays. The skate belongs to the class Chondrichthyes. This clade is represented today by sharks, sawfish, rays and skates. A clade within this diverse family, the Neoselachii, emerged by the Triassic, with the best-understood neoselachian fossils dating from the Jurassic. Fossil denticles (tooth-like scales in the skin) resembling those of today's chondrichthyans date at least as far back as the Ordovician, with the oldest unambiguous fossils of cartilaginous fish dating from the middle Devonian. Skates belong to the ancient lineage of cartilaginous fishes. Early Eocene fossil stingray Heliobatis radians
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