Sharks

Tiger shark - God's amazing creature
Image Animal Discovery

Shark must be one of the most amazing and successful creatures God has made in the blue seas of Earth. Fossils are found starting from Middle Devonian and it has survived till modern days. The first real threat to its existence are the humans who massacre these marvellous animals for food and for fun at the rate of over 100 million a year.

Scientific sons of Adam have named them Chondricthyes from Greek khondor ikhthys, cartilage fish.   

Evolutionary biologists suggest that sharks are relatives of placodermi covered by cartilage instead of protective bony armour plates. Dropping the heavy knights iron turned out to be a great decision - heavily protected placodermi perished at the end of Devonian sharks are doing very well, thank you, except for the threat from the even more successful land dwelling bi-pedals ruling over all life on this planet.

Shark tooth
Because sharks body is cartilage and not bony with calcium Devonian fossils are quite rare if existent at all. However, their presence from Middle Devonian on can be deducted from the numerous tooth fossils that have survived.

Image: kidszone.ws

Shark tooth from Eocene and Pliocene sediments
Bolton Museum, Lancashire, UK

Fossil forum has a rare photo of a Devonian shark tooth discovered in 2009 Holy Cross Mountain, Kowala, Poland.