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Fishes are a paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal taxonomy.Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes: [1]
In practice, feeding modes lie on a spectrum, with suction and ram feeding at the extremes. Many fish capture their prey using both suction pressure combined with a forward motion of the body or jaw. [85] Most fish are food opportunists, or generalists. They eat whatever is most easily available. [86]
Fishes of the World is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classification of the 30,000-plus fish species known to science.
Common names of fish can refer to a single species; to an entire group of species, such as a genus or family; or to multiple unrelated species or groups.Ambiguous common names are accompanied by their possible meanings.
Actinopterygii (/ ˌ æ k t ɪ n ɒ p t ə ˈ r ɪ dʒ i aɪ /; 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]
Class Cephalaspidomorphi - lampreys; Superclass Gnathostomata Vertebrates with jaws Class Chondrichthyes (cartilagineous fish - sharks and rays) Class Osteichthyes (bony fish), which has two subclasses: Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Full details of higher order fish taxonomy can be found in the Chordata article.
The body lacks scales, but is covered in easily abraded, silvery guanine, which imparts a greenish to purplish iridescence in life. The gas bladder is absent and the stomach is highly distensible. The transparent fins are spineless ; the deeply forked and hypocercal caudal fin is most striking, with the lower lobe extended to a length exceeding ...
A subclass of the Osteichthyes, the ray-finned fish (Actinopterygii), have become the dominant group of fish in the post-Paleozoic and modern world, with some 30,000 living species. The bony (and cartilaginous) fish groups that emerged after the Devonian were characterised by steady improvements in foraging and locomotion.