1. WESTERN MINDANAO STATE UNIVERSITY
COLLEGE OF SCIENCE& MATHEMATICS
DEPARTMENT OF BIOLOGY & NATURAL SCIENCES
ZOO-LEC 160 ANIMAL SYSTEMATICS
MARCH 13, 2014

2. • The Class Chondrichthyes has two subclasses:
–Elasmobranchii, which includes the sharks and rays.
–Holocephali: the chimaeras: ratfish and ghostfish.

3. 16.1

4. 16.2
Figure 24.02

5. • Modern Chondricthyes include the sharks, rays and Chimeras.
• The Chondrichthyes’ well-developed jaws, highly developed sense
organs, powerful swimming ability and streamlined shape have
enabled them to thrive as marine predators for more than 350
million years, as other groups have come and gone.
• There are just under 1000 living species, all of which have
cartilaginous skeletons, even though they are descended from
ancestors that had bone.

6. • The Chondrichthyes are an ancient group that although not
as diverse as the bony fishes have persisted largely
unchanged for hundreds of millions of years.
• The oldest unambiguous Chondrichthyans are found in the
Early Devonian (Devonian -- 416-360 mya). although there
are older fossils of scales.

7. • One of the best known extinct genera is Cladoselache a
pelagic marine predator from the Devonian.
• It was shark-like in appearance. About 2 meters long with a
large gape and three-pronged teeth. As in modern sharks
the teeth were arranged on a ligamentous band in a whorl-
shaped arrangement.

8. • Cladoselache had two dorsal fins, each preceded by a large
spine.
• It also possessed paired pelvic and pectoral fins as in
modern sharks, but the fins were much more broad based
than in later sharks.
• The tail was symmetrical externally, but internally
asymmetrical with the notochord extending into the upper
lobe of the tail.

9. Cladoselache picture
http://www.dinosoria.com/poissons/cladoselache_03.jpg
Cladoselache
Cladoselache lacked the rostrum (snout) of modern sharks

10. • By the Jurassic (200-146 mya) sharks of modern appearance had
evolved. Several genera from that era are still extant.
• The most distinctive feature of modern sharks is the rostrum or
snout that overhangs the mouth.
• Less prominent, but also of major importance was the evolution of
solid calcified vertebrae.
• Finally, the teeth are covered with thicker more complex enamel
than in earlier sharks.

11. • Megalodon (Carcharodon megalodon) is
another extinct shark species that is the
largest predatory shark known.
• Megalodon occurred from 28-1.5 mya and
at approximately 16m long (and with a
mass estimated at 47 metrics tonnes) it
resembled a massive great white shark
and was the top ocean predator of its era.

12. “Megalodon (gray and red) with the whale shark (violet), great white shark
(green), and a human (blue) for scale. Note: The maximum size attained by C.
megalodon is indicated by the 20 m scale.” From Wikipedia.
http://upload.wikimedia.org/wikipedia/commons/thumb/0/07/Megalodon_scale1.p
ng/220px-Megalodon_scale1.png

13. http://upload.wikimedia.org/wikipedia/comm
ons/thumb/7/71/Megalodon_tooth_ruler.jpg/
220px-Megalodon_tooth_ruler.jpg
http://upload.wikimedia.org/wikipedia/comm
ons/thumb/7/7a/Megalodon_shark_jaws_mus
eum_of_natural_history_068.jpg/300px-
Megalodon_shark_jaws_museum_of_natural_
history_068.jpg