Jurassic fish (?) tooth for ID

[RuMert]

Hi, what do you think of this tooth? It's of round section (at the base), has carinae, rooted probably. Possible ID: Eutrichiurides, Lepisosteus or maybe something like croc? Middle Tithonian, Jurassic, Moscow, Russia (marine environment). 7 mm length.

 

Provenance is not crucial, IMHO, if you have something similar, for example, from Dorset, please let me know.

 

"frontal" view

 

round base 

 

"side view", carinae

 

a "head" is visible here, it was probably the part that stuck out of the jaw

 

view from above, sorry for blurriness

[Tomasz]

Can't help too much, but my bet is for a crocodilian tooth. It looks as a massive tooth with rounded base of the root. 

[Natalie81]

I also get a croc vibe. Nice tooth! 

[pachy-pleuro-whatnot-odon]

My initial impression was that this would be a crocodile. However, I now wonder whether it is. The robustness of the tooth and thickness of the folds would all seem to point towards crocodile, where there are plenty of examples of such morphological features - as do the carinae. Fish teeth - to my knowledge, at least - are generally much more gracile, often smooth, and frequently compressed. Yet, you say this is a marine environment. Of course, we can't rule out that a single tooth like this ended up at sea, having been washed in by a river, coming from an estuary, or simply by the animal itself having entered the sea, but this is not a common scenario.

 

Also, the tooth has a number of features that throw me off from it being crocodile. Crocodile teeth frequently show horizontal banding, which is not present here. Instead, the tip of the tooth is much lighter, which is a trait I've seen more frequently with fish than in crocodilian teeth. Similarly, the top of the tooth seems slightly expanded vis-à-vis the rest of it, which, again, is a trait I know more from fish than crocodiles. Below are some examples, taken from Fossiles Boulonnais (which describes finds from the area around Bolougne-sur-Mer, mostly dating to the Kimmeridgian):

 

Hypsocormus sp.: note the ligher-coloured tip, round shape of the tooth and striations.

 

 

 

 

 

 

 

Amiiform fish: note again the lighter-coloured tip and round shape of the tooth, as well as a slight widening at the top, and carinae.

 

 

 

 

 

 

Sphenodus sp.: note the rounded shape, lighter-coloured apex in the one, and the enamel folds in the other. Also note carinae in both.

 

 

 

 

 

 

So, I'm quite positive it's a fish tooth. It's just a matter of which one. And, unfortunately, I have too little experience with fish to help you out with that one...

Edited December 30, 2020 by pachy-pleuro-whatnot-odon
Changed my mind as to identification

[RuMert]

Thanks @pachy-pleuro-whatnot-odon! Yep, I'm looking for marine crocodiles, though they've been extremely rare so far. The teeth like this are not that rare: they are uncommon, but well-known from this site. They are usually assigned to some fish, usually Eutrichiurides (a guess). One of our leading marine reptile specialists also said it was fish (but not sure which), in part because of the tip's whitish enameloid. I found the tooth was similar to Atractosteus, a genus that 1st appeared in the Late Jurassic

[Ludwigia]

I think that this is an Ichthyosaurus tooth.

[pachy-pleuro-whatnot-odon]

18 minutes ago, Ludwigia said:

I think that this is an Ichthyosaurus tooth.

For the same reasons as described above - that is, the lighter-coloured and slightly expanded tip - I don't see this being an ichthyosaur tooth. Ichthyosaur teeth don't have these features. Also, the enamel folds are way to big and irregular to correspond to ichthyosaurian plicidentine. Another issue is that ichthyosaurian teeth don't usually have carinae: to my knowledge only Temnodontosaurus platyodon has carinae, but that species doesn't have any plicidentine-folds on the tooth-crown (specimens from the collection of the Natural History Museum in London):