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Elasmobranchii is one of the two subclasses of cartilaginous fish in the class Chondrichthyes, the other being Holocephali . 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. The teeth are in several series; the ...
Holocephali ("complete heads"), sometimes given the name Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. [1] The earliest fossils are of teeth and come from the Devonian period. Little is known about these primitive forms, and the only surviving group in the subclass is the order Chimaeriformes.
Chondrichthyes (/ k ɒ n ˈ d r ɪ k θ i iː z /; from Ancient Greek χόνδρος (khóndros) 'cartilage' and ἰχθύς (ikhthús) 'fish') is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage.
The symmoriiformes have been assigned to Cladoselachii by Goto et al. (1988), to Elasmobranchii by Williams (1998), and to Chondrichthyes by Sepkoski in 2002 and by Maisey in 2008. The uncrushed braincase of Dwykaselachus indicates that symmoriiforms are members of Holocephali , as much of the internal anatomy, including the otic labyrinth and ...
The class is divided into two subclasses: Elasmobranchii (sharks, rays and skates) and Holocephali (chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates, the extant members of which all fall into ...
The group containing chimaeras and their close relatives (Holocephali) is thought to have diverged from Elasmobranchii (the group containing modern sharks and rays) during the Devonian, over 380 million years ago.
[21] [1] One branch, known as Holocephali or Euchondrocephali, was far more diverse in the Paleozoic, but is only represented in the modern day by the rare chimaeras (Chimaeriformes). The other branch, Elasmobranchii, is much more diverse in the present, including modern sharks (Selachii), rays (Batoidea), and their extinct relatives. [21]
The Australian ghostshark (Callorhinchus milii) is a cartilaginous fish (Chondrichthyes) belonging to the subclass Holocephali ().Sharks, rays and skates are the other members of the cartilaginous fish group and are grouped under the subclass Elasmobranchii.