Holocephali
Chimaera cubana is found in the waters around Colombia, Cuba and Puerto Rico.
- Worldwide
The Holocephali ( = " Euchondrocephali " Grogan & Lund, 2000), in addition to the Plattenkiemern to which sharks and rays belong to the second subclass of cartilaginous fish. As the only extant order among them the chimaeras ( Chimaeriformes ). The animals appeared in the Upper Devonian, and were particularly numerous in the former fish fauna in the Carboniferous. During the Permian, especially towards the end of this period, most taxa became extinct. After law merely remained the sea cats as the only surviving group.
Features
In contrast to the Plattenkiemern, which usually have four gill openings at the Holocephali the gills are covered by a gill cover, which leaves open only one gill opening ( differently than edax on the image of Sarcoprion ). The skin of the chimaeras and some fossil forms is naked. In many extinct Holocephali the skin, however, was covered as with the Plattenkiemern of placoid scales. Holocephali have no ribs, they lack the stomach. Many of the subtaxa are known only by dental and dental plate findings, as the stratigraphic range was complicated by the soft cartilaginous skeleton of the fish. It is therefore uncertain whether the characteristics apply to all subtaxa.
System
The systematics of Holocephali is still very uncertain. They are divided according to their types of teeth in two superorders. Here, the classification according to Nelson ( 2006) is reproduced. Other scientists organize some taxa, such as the Eugeneodontiformes, outside the Holocephali as a basal Chondrichthyes.
Paraselachimorpha
The members of the superorder Paraselachimorpha have haiähnliche teeth are continually replaced. All Untertaxa the Paraselachimorpha are extinct. The superorder is paraphyletic policy.
- Order Orodontiformes †
- Order Petalodontiformes †
- Order Helodontiformes †
- Order Iniopterygiformes †
- Order Deebeeriiformes †
- Order Eugeneodontiformes † (assignment very uncertain)
Holocephalimorpha
The members of the superorder Holocephalimorpha ( = " Holocephali " Grogan & Lund, 2000) possess a few large tooth plates, which serve the crushing of solid food. All orders of Holocephalimorpha up on the recent chimaeras are extinct.
- Order Psammodontiformes †
- Order Copodontiformes †
- Order Squalorajiformes †
- Order Chondrenchelyiformes †
- Order Menaspiformes †
- Order Cochliodontiformes †
- Order chimaeras ( Chimaeriformes )