They had neither an anal fin nor claspers. 5 gill slits were on each side of the head. Fossil have been found in the Cleveland shales including fossilized stomach contents which reveal that they ate fish. They show the distribution and origins of shared characteristics. Cladograms are testable hypotheses of phylogenetic relationships.
Male sharks have claspers.
In classification, a class is a group of related or similar organisms. A class contains one or more orders. A group of similar classes forms a phylum. The classification of organisms helps in the their study. Many reptiles are ectothermic.