On the Use of Antigenic Relationships Among Species for the Study of Molecular Evolution III.

Abstract

The acquisition of new and loss of primitive lens antigens among various superorders of Actinopterygii as well as among different orders of Teleostii were found to parallel evolutionary sequences based on palaeontological studies. Phylogenetic analysis of all the accumulated data on organ specific antigenic lens molecules in various classes of jawless and jawed fish agrees with paleontological evidence in showing that the Agnatha were the 1st vertebrates to appear. From the Agnatha descended the ancestor of all jawed fish. The latter appears to have formed 2 branches. One led to primitive Choanichthyes, represented now by the modern lungfish, and the other led to some other form of primitive jawed fish which was ancestral to the bony Actinopterygii represented today by the bichir, and to the cartilaginous Chondrichthyes represented by the modern shark. However, on the basis of morphological consideration, the Actinopterygii are being classified by zoologists as more closely related to the Choanichthyes than to Chondrichthyes. The evidence from lens antigens indicates that the land vertebrates could not have descended from some ancient lungfish, but from some later form of the jawed fish.