The frilled shark Chlamydoselachus anguineus is considered a living fossil, a prehistoric animal, and it is surely one of the most ancient animal that today the man knows.
This fish, called also eel shark for its form particularly lengthened, swims in the deep waters of the oriental Atlantic ocean, and of the oceans Pacific and Indian.

Its middle dimensions are of 150-170 cm, thin to a maximum of 200 cm, even if legends that go up again to end '800 narrate of samples of Chlamydoselachus anguineus more of seven meters length..
Instead reality tells that it is not known a lot about the biology and the behaviors of this fish, also because it has a preference for very deep waters, from 120 m to around 1200 m rarely going up again in surface.  There are little, also for this motive, the sightings and the captures realized by the man. 

The Chlamydoselachus anguineus has been described for the first time in 1884 from S. Garman even if already three years before R. Lawley, finding again some teeth of the animal in matter, drew near a lot to its discovery. 

The morphology of the frilled shark is surely particular: 

1) The mouth is in frontal position, contrarily of the present ventral mouth in the modern sharks. 

2) The teeth are tricusps, with three points (cusps), one central and two side slightly smaller.  This dental apparatus serves for plundering small fishes, molluscs and shellfishes. 

3) The caudal fin is very lengthened, to form of lance, and it is present only the superior lobe. 

4) It possesses six gills (in almost all the sharks they are five), very wide, almost to unite themselves in both the sides and they is fringed, there are present small portions of skin similar to fringes. 

5) The only dorsal fin is very small and behind, in correspondence to the anal fin and also the pectoral fins are short and rounded.

The reproduction is probably viviparous without placenta (the eggs open inside the maternal uterus) and the periods of pregnancy seem to be very long. 

The coloration of the frilled shark is brown dark color or grey, in both cases enough uniform in the whole body. 

As already mentioned, because of its "deep" habits, it is almost impossible to meet the Chlamydoselachus anguineus during an immersion (scuba) and the few exemplary that have been observed come almost always found inside the nets of the oceanic fishing-boats.
(See frilled shark video here)

Marco Angelozzi - www.prionace.it

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