CHEIROLEPIS 



^dorsal fin 



STEGOTRACHELUS 



PTERONISCULUS 



Figure 2-16. Three palaeoniscoid fishes as restored. Stegotrachelus and Cheiro/epis are from the 

 Upper Devonian, and Pteroniscu/us is Triassic. 



ACENTROPHORUS 



PARASEMIONOTUS 

 Figure 2-17. Two fossil hoiosteans. Acentrophorus, from the Permian, Parosemionotus, Triassic. 



HOLOPTYCHIUS 



EUSTHENOPTERON 



DIPTERUS 



Figure 2-18. Devonian fossil choonote fishes restored. 



OSTEOLEPIS 



32 • THE VERTEBRATES AND THEIR EXTERNAL ANATOMY 



