Helicoprion (Part 2).

I've already posted Helicoprion before on my blog, as my very first post. But I have learned so much since then that I would like to write about some new information.

Helicoprion had a buzzsaw-shaped tooth whorl on its lower jaw, which is what it's famous for. The most up-to-date reconstruction suggests it being a shark-like fish with a long upper jaw and a long lower jaw. At the end of the lower jaw was where the tooth whorl was.

© Life Before the Dinosaurs 2012

Although it is sometimes reconstructed eating ammonites, the absence of broken teeth on most specimens of its tooth whorl suggests that instead of eating ammonites, it fed on animals such as squid, fish, and other animals without shells. 

Although most specimens of Helicoprion's tooth whorl are about 10 inches in diameter, one specimen has a diameter of about 2 feet, suggesting that this odd shark-like cartilaginous fish might have grown more than 32 feet long, which makes Helicoprion one of the largest cartilaginous fish of all time. Only Megaladon, which didn't appear until the Tertiary period, was larger.

© Shark Trust

Fossils of Helicoprion have been found all over the world, as far apart as Australia and North America. The first remains were found in Russia and were named Helicoprion bessonovi. Other fossils of Helicoprion bessonovi have been found in China, which is not surprising to me because they were nearby. At the time that Helicoprion lived, all the continents were together, which probably explains why it has been found in so many places. In the United States, fossils of Helicoprion are found mostly in the western states, near where fossils of the related Edestus have been found. 


Helicoprion lived from the Carboniferous to the Triassic, which is quite a long time for a single genus to be around.

© Oleg Lebedev 2009

References:

http://www.wired.com/wiredscience/2011/03/unraveling-the-nature-of-the-whorl-toothed-shark/

http://www.paleospot.com/galerie_rubrique.php?rub=2 (lots of amazing illustrations of prehistoric sharks)

http://gsa.confex.com/gsa/2011RM/finalprogram/abstract_187593.htm

http://en.wikipedia.org/wiki/Helicoprion

Conodonta.

Conodonts were bizarre, fish-like probable chordates that may have resembled modern lampreys. They first evolved in the Cambrian, or possibly even the Precambrian, and died out in the Triassic-Jurassic extinction.

Conodonts were eel-shaped in form and most had large eyes, at least in comparison to the body. They had various toothy blades in the mouth to form what is known as "the conodont apparatus," which vaguely resembles the radula of a snail or slug.

Conodonts were probably capable of maintaining a cruising speed, but could not perform bursts of speed because their eel-like form would probably get them all tangled up. They would then be easy prey for any kind of predator trying to eat them. They probably swam in about the same style as an eel or loach. Although they had sharp teeth, they probably were not predators. Instead, they supposedly used "the conodont apparatus" as a sort of baleen to filter plankton from the water.

The largest conodont that has been found so far is Promissum, which reached lengths of 16 inches. Specimens of Promissum can be found in the Soom Shale of South Africa. Unlike most conodonts, Promissum had smaller eyes relative to body size. Promissum was about as long as an average house cat's body, without the head or tail.

The fist conodont specimens found were its individual toothy bars known as "conodont elements."

References:

http://www.ucl.ac.uk/GeolSci/micropal/conodont.html

http://en.wikipedia.org/wiki/Conodont

http://oceans1.csusb.edu/cdont_art.htm

Helicoprion (Part 1).

There are a lot of different ideas about how Helicoprion might have looked. The "buzz saw" could have been in the jaw, and that's at least what I think. It also could have been anywhere on the entire body. Helicoprion lived Carboniferous to early Triassic. The name is pronounced hella-cuh-PRY-on.

The Helicoprion in the picture below may have helped it smash ammonite shells, or any other prey with a shell, including trilobites and other shelled animals. It may look like Sarcoprion, but Sarcoprion only has half a "buzz saw," and this idea of Helicoprion has a whole "buzz saw," but half of it is wedged into the inside of its jaw.

The Helicoprion in this last picture may have opened its mouth and let its "buzz saw" hang down while swimming through a school of fish. That way, it could kill many fish and easily just swim around in the school and eat freshly killed fish.