Chondrichthyes show three types of reproduction...
FISH -- EXTERNAL FERTILIZATION OF EGGS
KEPT IN MOTHER AND HATCH WITHIN MOTHER -- EGG HATCHES IN BODY
- ENERGY FOR EMBRYO SUPPLIED BY YOLK; INTRA-UTERINE CANNIBALISM
SEEN IN THE SAND TIGER SHARK WHERE THE FIRST BORN DEVOURS THE OTHER EMBRYOS
CONNECTION VIA UMBILICAL CORD
Originally thought to be primitive fish, sharks are actually
quite complex animals when further studied and have unparalleled sensory
capabilities and an uncanny ability to survive through the ages.
Sharks are one of the oldest and one of the most successful and diverse
vertebrate groups ever.