[2][3][4] From a practical point of view the life-history pattern of elasmobranchs makes this group of animals extremely susceptible to over fishing.

Members of this subclass are characterised by having five to seven pairs of gill slits opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin.

Some authors consider it as equivalent to Neoselachii (the crown group clade including modern sharks, rays, and all other descendants of their last common ancestor).

Members of the elasmobranchii subclass have no swim bladders, five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, and small placoid scales.

[5][13] The oldest unambigous total group elasmobranch, Phoebodus, has its earliest records in the Middle Devonian (late Givetian), around 383 million years ago.

[15] During the Carboniferous, some ctenacanths would grow to sizes rivalling the modern great white shark with bodies in the region of 7 metres (23 ft) in length.

Bonaparte's original definition of Elasmobranchii was effectively identical to modern Chondrichthyes, and was based around gill architecture shared by all 3 living major cartilaginous fish groups.

Maisey (2012) suggested that Elasmobranchii should exclusively be used for the last common ancestor of modern sharks and rays, a grouping which had previously been named Neoselachii by Compagno (1977).

[7] Other recent authors have used Elasmobranchii in a broad sense to include all chondrichthyans more closely related to modern sharks and rays than to chimaeras.

[23][24][25][26] The 5th edition of Fishes of the World sets out the following classification of the Elasmobranchs:[29] Recent molecular studies suggest the Batoidea are not derived selachians as previously thought.