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Sharks
Chris Hinton

Historical Geology

Roger Weller

Frilled Sharks

 

Photograph taken from National Geographics

           

            The Frilled Shark is one of the few ‘living fossils’ that mankind has found still alive and active in the world today despite originating in the Late Cretaceous Epoch, specifically the Campanian period. As one can see from the picture the Frilled Shark gets its name from the ‘frilled’ nature of its gills, puffed out in the picture above.
 

           

            Photograph taken from National Geographic
 

            It has a vaguely eel-like shape with few of the features we commonly associate with sharks. The dorsal fin is a long and ridge like, very different from the usual triangular dorsal we‘re so used to seeing. The pectoral fins are of an unusual shape, broader, more like spades or paddles than the cut sharp-looking standard. The tail, instead of being the broad, creased fin we see so often is instead a billowy trailing mass akin to that of a Siamese Fighting Fish or, as previously mentioned, an eel. Most interestingly the Frilled Shark’s teeth are absolutely one of its most unique features.
 

 

            As we can see here it has a unique almost shell-like construction, perfect for keeping an unyielding hold on anything it bites into. This style of tooth is known as tricuspid. Despite the fearsome appearance of its teeth the shark poses absolutely no threat to humans. The worst one could expect is a bite on the hand from a scientist examining one.
 

            The shark’s usual diet consists of other sharks, small squid, and various bony fish. In essence, anything it can tear a chunk out of that lives on its depth level.
 

            The Frilled Shark’s proper name is Chlamydoselachus anguineus. It is the only member of the Chlamydoselachidae family in the Hexanchiformes order making it exceedingly rare.

 

Photograph from marinethemes.com
 

            The shark’s usual habitat is deep, cold ocean water in startlingly different places as the map shows. The spots outlined in the brighter blue are the locations around the world where the Frilled Shark has been most frequently sighted.
 


 

            Most impressively, a female Frilled Shark was captured alive off the coast of Japan in 2007. It was initially discovered by local fishermen who described it to scientists as an ‘eel-like creature with razor-sharp teeth’. The Japanese scientists, upon investigating the call, quickly captured the Frilled Shark and brought it to an aquarium where they were able to record it swimming. Unfortunately the shark died several hours later. Scientists have since theorized that the reason for its being near the surface of the water, a rarity, was due to some injury. The cause of its death is presumed to be the Frilled Shark’s inability to adapt to the warm salt water of the aquarium tank. In essence, the shock of the new environment as well as the aforementioned injury resulted in its death.
 

                                                                               Photograph taken from National Geographic

            One particular mystery has been slowly clearing up thanks to tireless research. That is, namely, how the Frilled Shark reproduces. The answer is quite simply: A lot like how any other shark does. Via young developed inside the shark and birthed alive. The Frilled Shark procreates year round due, undoubtedly, to the whopping forty two month gestation period. That knocks the African Elephant, at 22 months, completely out of the water for longest vertebrate gestation period. Common theory holds that this is due to the fact that the Frilled Shark lives in the dark, deep, cold waters and so its metabolic rate among all other functions is significantly slower. The Frilled Sharks gives birth to litters of approximately six to twelve pups. Rather few for the average shark but given the Frilled Shark’s relatively small size, averaging between three to four feet, this can be expected. In fact, the female shark is often the larger, growing closer to that four foot mark, and it is assumed that the extra space it taken up by womb to allow the pups room to develop properly.
 

            Despite the average being three to four feet there have been cases of the Frilled Shark growing up to six feet. For a deep-ocean dweller that’s a tremendously large size.

 

Photograph taken from National Geographic
 

            Despite the many millions of years the Frilled Shark has existed it shows very little in the way of evolution. It has retained the same basic shape and function from its inception nearly eighty four million years ago. A telling sign of just how perfectly adapted to their environment sharks are and what a perfect species they have become through millions of years of highly specialized, nearly unnoticeable, evolution.

 

References

http://www.fishbase.org/Summary/SpeciesSummary.php?id=635

http://news.nationalgeographic.com/news/2007/01/photogalleries/frilled-shark/photo4.html

http://educatedearth.net/video.php?id=2844

http://www.elasmo-research.org/education/ecology/deepsea-frilled_shark.htm

http://www.shark.ch/Database/Search/species.html?sh_id=1049