Now that we've met several very different species of sharks, it's time to look at their ancestors. And to help us do that, here are a few books and things to consider. First up is the DVD of a very interesting series from the BBC called Chased by Sea Monsters. Nigel Marvin, TV-naturalist extraordinaire, does an in-the-field (or water, in this case) nature show with CG prehistoric sea creatures. It's a bit of a weird spin on "Swimming With Dinosaurs," but very cool, and it gives you a good idea about the possible sizes and movements of animals long since extinct. And there is a companion book for the series as well. Get the DVD here and the book here!
The other book of the day is really fun, and even more fun for kids who like strange beasties: Encyclopedia Prehistorica: Sharks and Other Sea Monsters is a very bold yet intricate pop-up book with all kinds of scary prehistoric creatures to marvel at. Grab it here.
According to the fossil record, sharks have been around for over 450 million years, which makes them older than the dinosaurs (the first dinosaurs only appeared about 230 million years ago)! Many of the earliest fossil remains (mostly teeth) have been found in Australia and Antarctica, which might indicate that sharks started out their long dynasty in the Southern hemisphere, back when there were only two continents.
They started out very primitive, with scales that do not resemble modern sharks' skin very much. The scales, along with teeth, provide an excellent fossil record, however, especially for earlier species. Many kinds of prehistoric sharks lived in freshwater, and had fixed jaws and reproduced through external fertilization, unlike modern sharks. And they were very diverse, as normal- or weird-looking as modern sharks. For an example of a weirder one, check out Stethacanthus, whose oddly-shaped dorsal fin was probably used by males for courtship purposes. But considering that this strange beast lived between 370 and 345 million years ago, who really knows?
The more direct ancestors of modern sharks began to appear about 100 million years ago. Enough species survived the apocalypse at the end of the Cretaceous period 65 million years ago to evolve into the sharks that we see today. Of the more recent prehistoric species, Megalodon is probably the most famous. This huge shark (which resembles the great white in many ways) fed on whales and other huge marine animals. It had a relatively recent and short lifespan as a species; from about 16 million years ago up to 1.6 million years ago, according to the fossils found. Even though there have only been fossil teeth and vertebrae found, palentologists figure from their size that Megalodon was about 14 to 18 meters (or 46 to 58 feet) in length. To get a bit of perspective, here's a nice scale drawing for you.
You wouldn't even be a hearty snack for this guy. It is believed that they fed mostly on baleen whales, and one theory to why they became extinct is simply a lack of whales for them to eat.
Fossil tooth image from www.fossilien.de; megalodon and diver image from Wikipedia.
With the advent of the novel Meg and other buzz about Megalodon in popular culture, it's no wonder that this huge predator is living again, at least as a buzz word. But some folks are convinced that there are still Megalodons hanging out somewhere in deep water, just waiting for the right moment to resurface. Because biologists believe Megalodon's habitat was in relatively shallow seas, this is unlikely, but there are prehistoric sharks that are still around. And we know because we've seen them.
Recently in Japan, there have been sightings of two sharks of a prehistoric nature. No, these individual sharks are not millions of years old, but the species they belong to are. Cow Sharks and Frilled Sharks are 150 million and 95 million years old, respectively. Frilled Sharks were re-discovered in the 19th century, and dead ones had been found occasionally, but in January of 2007, a live Frilled Shark was found off the coast of Japan and taken to a marine park. Sadly, it was in ill health, and died soon after arriving. There is some amazing video footage of this prehistoric beast, however:
Our other favorite prehistoric shark here at Needcoffee is the Goblin Shark, which we covered here earlier. It lives about 1200 meters under the water, although this notion is being challenged now due to stomach contents of some specimens indicating that they may feed higher up in a mid-water range. Although most have been found off the coast of Japan, goblin sharks have been seen almost all over the world, even in the Gulf of Mexico. The goblin shark is bright pink, and has an unusual feeding habit. When prey is near, the shark extends its jaws to snatch it up. This extension of its jaws is what gives it its odd appearance. When the shark isn't feeding, it just looks more like a normal shark with a long snout.
Only four days after the live Frilled Shark was caught, a Goblin Shark was caught, off the coast of Japan as well, and transferred to a marine park, where it only survived a couple of days. There is also video footage of this rare fish as well, though:
Sharks. They predate the dinosaurs, and were around even before Bob Barker! See you guys tomorrow for our final day of Needcoffee's Shark Week.
Continue to Day Seven