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Actinopterygii (/ ˌ æ k t ɪ n ɒ p t ə ˈ r ɪ dʒ i aɪ /; from Ancient Greek ἀκτίς (aktis) 'having rays' and 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]
Both its major subgroups are successful today: Actinopterygii includes most extant bony fish species, and Sarcopterygii includes the tetrapods. Euteleostomes originally all had an endochondral bone, fins with lepidotrichs (fin rays), jaws lined by maxillary, premaxillary, and dentary bones composed of dermal bone, and lungs.
Their skeletal structure has evolved towards greater lightness. While teleost bones are well calcified, they are constructed from a scaffolding of struts, rather than the dense cancellous bones of holostean fish. In addition, the lower jaw of the teleost is reduced to just three bones; the dentary, the angular bone and the articular bone. [8]
Archaeopteris is a member of a group of free-sporing woody plants called the progymnosperms that are interpreted as distant ancestors of the gymnosperms. Archaeopteris reproduced by releasing spores rather than by producing seeds, but some of the species, such as Archaeopteris halliana were heterosporous, producing two types of spores.
Chordate fossils have been found from as early as the Cambrian explosion over 539 million years ago. [11] Of the more than 81,000 [ 12 ] living species of chordates, about half are ray-finned fishes ( class Actinopterygii ) and the vast majority of the rest are tetrapods , a terrestrial clade of lobe-finned fishes ( Sarcopterygii ) who evolved ...
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.
The name 'vertebrate' derives from the Latin vertebratus, 'jointed', [8] from vertebra, 'joint', in turn from Latin vertere, 'to turn'. [ 9 ] Fossilized skeleton (cast) of Diplodocus carnegii , showing an extreme example of the vertebral column that gives the vertebrates their name.
The plant produces dense clusters of tiny white flower heads held above the foliage. In Illinois, the plant blooms during late summer and early fall. [6] Its native habitats include damp prairies, bogs, and alluvial woods. [7] Eupatorium perfoliatum can form hybrids with other species of the genus Eupatorium, for example Eupatorium serotinum. [3]