Discovery Channel

Evolution of a shark

Evolution

Megamouth shark (Seapics.com)
Shark Evolution

Sharks have been around for a very long time. The first known sharks evolved about 400 million years ago, more than 200 million years before the dinosaurs, and were very common predators. Over 2,000 species have been identified from the fossil record, compared to the 1,000 or so species known to exist today.

The earliest known sharks were very different in appearance from their modern counterparts. Some looked more like eels than fish. Many of them had rounded snouts, rather than the pointed ones we associate with today’s sharks. They had smaller brains and their teeth were smooth, rather than the sharp-edged or serrated teeth typically seen in modern sharks. Their fins were less flexible and manoeuvrable, and it’s likely that ancient sharks were less agile than their modern cousins. But in some ways they were very similar to the animals we call sharks today, having the same cartilaginous skeletons, multiple gill slits and replaceable teeth.

Photo: Seapics.com
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