ABSTRACT
Hagfishes and lampreys (adults, Fig. 6.1) have traditionally been placed together in the Agnatha, the jawless craniates. A biting apparatus differing from that of gnathostomes in not being derived from gill arches is present in some fossil forms (Nelson 2006). The terms Agnatha or Cyclostomata are not formally recognized here in view of albeit controversial evidence that it is a paraphyletic group (see below). Figure 6.2 illustrates two alternative views of their relationships with each other and with gnathostomes.
