Home | | The Diversity of Fishes: Biology Evolution and Ecology | Subclass Cladistia - Class Actinopterygii, Advanced jawed fishes : teleostomes (Osteichthyes)

Chapter: The Diversity of Fishes: Biology, Evolution, and Ecology: A history of fishes

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Subclass Cladistia - Class Actinopterygii, Advanced jawed fishes : teleostomes (Osteichthyes)

After a great deal of effort and no small amount of controversy (see Nelson 1994; Helfman et al. 1997), the weight of opinion has shifted to recognize the modern polypteriforms as a separate subclass and the sister group of the other two subclasses of actinopterygians, the Chondrostei and Neopterygii.

Subclass Cladistia

 

After a great deal of effort and no small amount of controversy (see Nelson 1994; Helfman et al. 1997), the weight of opinion has shifted to recognize the modern polypteriforms  as a separate subclass and the sister group of the other two subclasses of actinopterygians, the Chondrostei and Neopterygii. Also referred to as brachiopterygians, fossil cladistians are known only as far back as the Middle Cretaceous of Africa and Late Cretaceous of South America. This represents a dramatic gap in the fossil record for a group considered more primitive than other actinopterygians, which are known from the Devonian (cheirolepidiform and palaeonisciform chondrosteans) and the Triassic (semionotiform neopterygians). The placement of “Polypteriformes(?)” on Fig. 11.23 within the Chondrostei is probably incorrect, but their mixture of primitive, advanced, and unique traits makes resolving their position within the Actinopterygii challenging.




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