Welcome to the Paleo-Shark Pages!|
Fossil Photo Credits: John G. Maisey, Division of Paleontology, American Museum of Natural History
1. Since cartilage rapidly disintegrates, sharks are seldom preserved as fossils. The fossil record of sharks consists mainly of teeth and spines from their fins.
2. The earliest record of sharks is isolated spines, teeth, and scales that appeared 350 to 400 million years ago in the Devonian period, known as the "Age of Fishes".
3. Modern-day sharks completed evolution in the Carboniferous period, 280 to 345 million years ago.
4. One fossil shark known today from it's enormous fossil teeth, Carcharodon megalodon (pictured below) lived in the Miocene period, 10 to 25 million years ago.
"Millions of years ago, the oceans were inhabited by one of Earth's most fearsome predators... giant sharks. Just exactly how large these sharks were and what they looked like is still a matter of speculation, since they have left behind little evidence of their existence.
Because sharks have skeletons of cartilage rather than bones, all that remains of these long-gone monsters of the deep are their fossilized teeth, some of which are nearly 6 inches long and weigh 12 ounces. They are somewhat similar in shape to the teeth of present-day great white sharks, but about four times the size, earning these prehistoric sharks called megalodon the nickname "megatooth."
Based on their large tooth size, scientists once believed these sharks must have grown to gigantic proportions of 120 feet or more in length. Recent reconstructions have shrunk megatooth down to 50 to 60 feet, which is still formidable. Imagine a shark the size of a city bus!
Because there are so few fossil remains of megatooth sharks, there is still some debate as to how to classify them (in the genus Carcharocles or Carcharodon), but scientists are gradually developing a profile of what these huge sharks must have looked like and how they lived."
Source: Discovery Online
5. Sharks and rays have remained relatively unchanged for the past 280 to 345 million years.