Sharks have form and different dimensions: there is for instance the great white shark (Carcharodon carcharias), that reaches the 7 m, or the whale shark (Rhincodon typus) that can reach even 18 m of length, but also very small sharks exist, animals that would comfortably be in the palm of one hand..
We are currently speaking about the smallest known sharks: the Etmopterus perryi and the Etmopterus carteri, respectively dwarf lanternshark and cylindrical lanternshark, that reach a maximum length of 21 cm.
To the third place of this particular classification there is the pygmy ribbontail shark, Eridacnis radcliffei, whose maximum dimension is of 24 cm.
These three small cartilaginous fishes are less known to the great public in comparison to theirs "big brothers", but not for this their biology results less interesting and deprived of consideration.. 

Only some aspects of their behavior and their vital cycle are currently known and really for this motive there will be interest about close examinations and specific studies, bringing to scientific searches on the field, trying to resolve all the mysterious aspect that don't allow to know well these strange inhabitants of the sea depths.
We speak about deep waters becouse these small sharks swim to a depth of 300 m and these habits constitute the greater obstacle to a correct scientific close examination..
Their formalities of reproduction are almost unknown, the longevity, the ransom to the birth, the reproductive age and also the development of the populations. (if the number of these sharks is in growth, stable or in decrease..) 

Despite all some information, due above all to the study of samples accidentally captured, are known by the biologists and profits in this case to introduce a small card of each of these three small shark, with their principal characteristics:

Etmopterus carteri  (max: 21 cm)

This shark has black body, uniform, the face is short and rounded off and the head, as it suggests the name, has a cylindrical form.
The gills are enough ample and also the eyes of this small shark, in proportion with the total length, are very great to look to every movement in the depths in which it swims, where little brightness helps the vision of these creatures. 

The two dorsal fins are of averages dimensions and before each of them is present a strong grooved thorn, precious defense tool against the attacks of the raiders. The pectoral fins are lobate while the anal fin is absent.
This shark swims to depth that oscillates among 280-350 m and it seems to exclusively be present in the waters in proximity of the Caribbean coasts of Colombia. 

It doesn't have commercial value, probably for its redoubts dimensions and currently the  develop of the population is not known. (if the number of Etmopterus carteri is in decrease, stable or in growth)
 

Etmopterus perryi  (max: 21 cm)

Also this shark belongs to the family Etmopteridae, the most numerous of the order Squaliformes. The name of this shark is due to the presence of the photoforis, characteristic bright elements present above all around the mouth and along the sides, with the function to attract small preys creatures, attracted by these weak bright in an almost complete obscurity. 

In fact also this lanternshark normally swims in deep waters, among 280-430 m of depth, always in proximity of the Caribbean coasts of Colombia.
The body of the Etmopterus perryi is of dark brown color on the back, almost black the ventral part, with lines and diffused motives that interrupt this coloration.
The face is lengthened and the eyes are great, proper for the vision in poorly illuminated waters and the two dorsal fins, of average dimensions, are preceded by strong defensive thorns.
The gills are not very developed and the anal fin is absent.
The commercial value is scarce, probably for the redoubts dimensions.
The name Etmopterus perryi has been given in honor of the biologist Perry W. Gilbert in 1985.
 

Eridacnis radcliffei  (max: 24 cm)

Very small shark of dark brown color with characteristics dark banding in the two dorsal fins and in the caudal fin, to form of ribbon and with the superior lobe very developed.
The anal fin is present, very small, half of the dorsal fin. 

The face is lengthened and the eyes are middly developed, with the presence of a rudimentary nictitant membrane. The Eridacnis radcliffei can swim to elevated depth, from 70 up to 750 m and it is mainly diffused in the waters of India, Philippines, Vietman and in the Indo-Pacific.
Its principal preys are crustacean, squids and small bony fishes.
The reproduction is viviparous without placenta, with the development of 1-2 small sharks for every reproductive moment.
The name Eridacnis radcliffei has been given in honor of the naturalist Lewis Radcliffe.
 

Dwarf lanternshark
Etmopterus perryi
Springer & Burgess, 1985
Order: Squaliformes
Family: Etmopteridae

Middle dimension: 15-17 cm
Maximum dimension: 21 cm
Distribution: Caribbean coasts of Colombia
Coloration: dark brown color on the back, almost black the ventral part, with lines and diffused motives that interrupt this coloration.
Reproduction: viviparous without placentata.
Compare with the man: inoffensive
Commercial value: no commercial value, probably for its redoubts dimensions.

 

Cylindrical lanternshark
Etmopterus carteri
Springer & Burgess, 1985
Order: Squaliformes
Family: Etmopteridae

Middle dimension: 18-20 cm
Maximum dimension: 21 cm
Distribution: Caribbean coasts of Colombia
Coloration: black body, uniform.
Reproduction: viviparous without placentata.
Compare with the man: inoffensive
Commercial value: no commercial value, probably for its redoubts dimensions.

Pygmy ribbontail shark
Eridacnis radcliffei
Smith, 1913
Order: Carcharhiniformes
Family: Proscylliidae

Middle dimension: 15-18 cm
Maximum dimension: 24 cm
Distribution: India, Philippines, Vietman and in the Indo-Pacific.
Coloration: dark brown color with characteristics dark banding in the two dorsal fins and in the caudal fin.
Reproduction: probably viviparous without placentata.
Compare with the man: inoffensive
Commercial value: no commercial value, probably for its redoubts dimensions.

Bibliography: "Sharks & Rays, Elasmobranch Guide Of The World". Ralf M. Hennemann,
"Sharks of the world", Leonard Compagno, M. Dando, S. Fowler,

Marco Angelozzi - www.prionace.it

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