TABLE 15-3 THE PHYLOGENY OF THE VERTEBRATES ACCORDING TO JARVtK (1960) 



Dipnoi 



Urodela Anura 



\ .^ 



\ Labyrinthodont 



\ I 



Porolepi formes Osteolepiformes 



Sauropsida 



Therapsida 



Eiasmobranchii Placodermi 



Elasmobranchiomorphi 



Coelacanthiformes 

 * Branchiopter\'gii 

 Actinopterygii 



GNATHOSTOMATA 



Cyclostomi 

 Cephalaspidomorphi Pteraspidomorphi 



X 



Ostracodermi 



X . 



Eocraniata 



I 



Acrania 



AGNATHA 



Vertebrata 

 Protochordata 



periodically to radiating sidelines; some of these became 

 extinct and a few survived. An early branch gave rise to the 

 brachiopterygian type, while later ones gave rise to the 

 sturgeons and Lepisosteus. 



The living holosteans present a special problem. The dif- 

 ferences between Anna and Lepisosteus have long been known 

 (Hay, 1898), but these two kinds of fishes are still placed 



together, and the inference is that they are closely related. 

 Our examination suggests that although they do agree in 

 having lepidosteid tubes in their cranial bones, they dis- 

 agree in many features. The presence of lepidosteid tubes is 

 suggestive only of a functional parallelism in bone devel- 

 opment; it is not indicative of close common ancestry. Like 

 the brachiopterygian, Lepisosteus appears to be a relatively 



TABLE 15-4 BASIC PHVlOGENy Of THE VERTEBRATES AS SUGGESTED IN THIS TEXT 



Dipnoi 



Tetrapoda • 



Osteolepiformes * 



Porolepiformes 



Actinistia 



Brachiopterygii 



Lepisosteus 



Amia 



Teleostei 



Holocephal: 

 Arthrodira 

 Hagfish 

 Lamprey 



-Choanates 



GNATHOSTOMATA 



Protovertebrata 



VERTEBRATE PHYLOGENIES 



447 



