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However, the external shape of heterocercal tail fins can also appear symmetric (e.g. †Birgeria, †Bobasatrania). Heterocercal is the opposite of hypocercal Hypocercal, also known as reversed heterocercal, means that the vertebrae extend into the lower lobe of the tail, making it longer than the upper lobe (as in the †Anaspida). It is the ...
Fish anatomy. Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. [1] In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or ...
Actinopterygii. Actinopterygii (/ ˌæktɪnɒptəˈrɪdʒiaɪ /; from actino- 'having rays' and Ancient Greek πτέρυξ (ptérux) 'wing, fins'), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish [ 2 ] that comprise over 50% of living vertebrate species. [ 3 ]
The tail of a shark consists of the caudal peduncle and the caudal fin, which provide the main source of thrust for the shark. Most sharks have heterocercal caudal fins, meaning that the backbone extends into the (usually longer) upper lobe. The shape of the caudal fin reflects the shark's lifestyle, and can be broadly divided into five categories:
Sarcopterygii (/ ˌ s ɑːr k ɒ p t ə ˈ r ɪ dʒ i. aɪ /; from Ancient Greek σάρξ (sárx) 'flesh' and πτέρυξ (ptérux) 'wing, fin') — sometimes considered synonymous with Crossopterygii (from Ancient Greek κροσσός (krossós) 'fringe') — is a clade (traditionally a class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe ...
Sturgeon. Sturgeon (from Old English styrġa ultimately from Proto-Indo-European * str̥ (Hx)yón - [1]) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic ...
Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and rays (Neoselachii) as part of the clade Euselachii. They are distinguished from other chondrichthyans by ...
Acanthopterygii. Acanthopterygii (meaning "spiny finned one") is a superorder of bony fishes in the class Actinopterygii. Members of this superorder are sometimes called ray-finned fishes for the characteristic sharp, bony rays in their fins; however this name is often given to the class Actinopterygii as a whole.