(Korsvika - The Trondheim fjord / 20 meters / 1.19.2004)

Phylum: Chordata

Superclass: Agnatha

 

Norwegian: rundmunner

The Agnatha superclass includes the hagfish and the lampreys. They are the remains of an ancient class of vertebrates. Fossils as old as 500 million years (Cambrian period) indicate that this class has included more complex species. The classification of the few remaining species is at best, uncertain. A common feature is the absence of jaws and paired fins. Only extinct agnathans had bony skeleton.

The fertilization are believed to be external. Identification of the sex is impossible for juvenile hagfishes as each individual has both ovaries and testes. However, the gonads of only one sex are functional in adult hagfishes. The digestive system lacks a stomach.