• Class: Chondrichthyes
• Subclass: Elasmobranch
• Bottom-dwelling, characterized by diphycertal tail or deep water, characterized by heterocercal tail
• 0.15 m to 14m long
• Live in waters up to 2 km deep.
• The average length for a modern shark is 1.5 m
• Arose some 400 million years ago
• Sharks likely evolved from early Placoderms which lost the ability to produce proper bone
• “Simplified” skeleton was originally thought to be a more primitive trait but is now considered to be an advanced alternative to the less flexible skeleton made of bone
• Sharks are covered with tiny scales called denticles which are shed and replaced as the shark ages
• The males have sexual organs called claspers

bharris@chat.carleton.ca