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paleontologistinprogress

Misterious shark fin spine from Nothern Italy

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paleontologistinprogress

Hello everyone,

I'm a student in Milan and I'm currently struggling in trying to identify this fossil shark fin spine. Which taxon do you think it belongs to ?

This speciment had been found in Northern Italy. The exact stratigraphic position is yet to be determined, but I can say for sure it's either Upper Rhaetian or Lower Hettangian. The spine is almost 11 inches long (28 cm, 29,2 cm if you count the missing tip) and is yet incomplete, for it lacks the basal structure and there's a big gap at 1/3 of its lenght (see images below). It also shows a pattern of denticles near the tip ( they stop abruptly 10,5 cm from the tip). The internal morphology feature an enlarged cap layer, a thin enameloid layer (lacking in some spots) near the tip while wider near the base and a thin trunk layer. The lumen, the internal cavity, is rain drop shaped and is filled with matrix for more than half of the spine lenght.

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post-20015-0-91211500-1446671879_thumb.jpg

post-20015-0-47822900-1446671913_thumb.jpg

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Troodon

Any chance it belong to a Hybodus sp.

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Foozil

Very interesting, can't wait to get a positive ID :D All I can chuck in is its definitely a shark spine... :P

Welcome to TFF By the way

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non-remanié

I would say its from a chimaeroid fish.

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paleontologistinprogress

Thanks everyone for your replies and for welcoming me in this forum. As for my speciment, I considered it being an Hybodus sp, but it seem to lack the mthe tipical ornamentation of this genus and the internal morphology in transverse section seems of the speciment seems to differ ffrom that of an Hybodus (though I couldnt tell it for sure) . Moreover, an Hybodus fin spine tends to be much wider than my speciment. Despite all of that, I still would not dicard the Hybodus hypotesis completely. Right now, I'm prone to agree with non-remanié: I think that this fin spine belongs to a chimaeroid fish, and more in particular to a member of the Myriacanthidae family.

In fact, the general and internal morphology, the size and the proportions and even the stratigraphic collocation of my speciment seem to match that of a Myriacanthid pretty well ( see this article for more information http://retro.seals.ch/digbib/view2?pid=egh-001:1981:74::829).

What do you think? Do you agree in my interpretation or there's something I'm missing?

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MarcoSr

Unfortunately a number of key diagnostic features are not clearly visible from the pictures like the denticles and denticle pattern and the cross section. However my first impression seeing the surface texture was Chimaeroid fish.

Marco Sr.

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