tyrannosaur, shark or other?

[Myryad]

hello.

on a website i use to buy fossils from some seller posted this tooth and claims to be a tyrannosaur tooth. on reddit some people said it might be shark but other user told me to ask here as it might be some kind of troodon tooth.

 

could you please help me id it and make an idea of the value if i want to buy it?

 

thanks beforehand

[patelinho7]

We don't provide valuations here, but it's definitely a theropod tooth. Not shark, and not Troodon either. I would say it looks like a tyrannosaur tooth but I'm no expert on theropod teeth.

[Tidgy's Dad]

Looks theropod to me as well.

What information on the location was provided? 

[jpc]

looks too thin to be a tyrannosaur to me...

I would bet on dromaeosaur.  

[Myryad]

it just says hell creek formation. but nothing else, i mean it goes by trust i guess...

[trilobites_are_awesome]

Its a theropod tooth probably tyrannosaur. without locality it would be very hard to say what species.

Edited October 6, 2023 by trilobites_are_awesome

[trilobites_are_awesome]

Oops you posted locality at the same time i posted my post.

[Tidgy's Dad]

2 minutes ago, Myryad said:

it just says hell creek formation. but nothing else, i mean it goes by trust i guess...

Unwise to go by trust.

The seller may be an honest person, but may not be knowledgeable, could have made a genuine mistake, or may have been given the wrong information. 

[Myryad]

12 minutes ago, Tidgy's Dad said:

Unwise to go by trust.

The seller may be an honest person, but may not be knowledgeable, could have made a genuine mistake, or may have been given the wrong information. 

exactly, that's why i prefer to ask and make a better idea

[patelinho7]

Oh wait yes the proportions are off for tyrannosaur

[Frightmares]

Looks theropod. Definitely not Troodon. Hard to say much more than that. If it’s from Hell Creek, it could be Nanotyrannus. Doesn’t match the description of Acheroraptor.

[Rock Hound]

If you purchase it at a fair price for an unknown theropod tooth, you can feel confident that you got your money's worth.  It is from a theropod.

[Haravex]

There is a slight curve on the mesial serrations, indicating it is in fact Tyrannosaur, can't say any further than that due to lack of base and tip. 

[Psittacosaur9]

On 10/7/2023 at 7:14 AM, Frightmares said:

Looks theropod. Definitely not Troodon. Hard to say much more than that. If it’s from Hell Creek, it could be Nanotyrannus. Doesn’t match the description of Acheroraptor.

Isn't Nanotyrannus no longer a valid genus? Or does it still apply to teeth?

[Frightmares]

6 hours ago, Psittacosaur9 said:

Isn't Nanotyrannus no longer a valid genus? Or does it still apply to teeth?

I believe it's still all up in the air whether it's a juvenile rex or a valid genus. Anyone know if anything new has been published on this subject?

[Tidgy's Dad]

7 hours ago, Psittacosaur9 said:

Isn't Nanotyrannus no longer a valid genus? Or does it still apply to teeth?

The current general scientific consensus and the most recent paper seem to be in favour of Nanotyrannus being a juvenile Tyrannosaurus rex. 

But I doubt that we've heard the last of this. 

[Randyw]

Oooooo! The nano vs rex debate comes up again! ( Randy pops some popcorn and leans forward for a better view)

[Kikokuryu]

11 hours ago, Psittacosaur9 said:

Isn't Nanotyrannus no longer a valid genus? Or does it still apply to teeth?

At the very least, the teeth cannot be attributed to Tyrannosaurus rex regardless. If it doesn't look like T. rex, it simply shouldn't be called T. rex.

 

If Nanotyrannus isn't valid, then all of the Nano teeth from Hell Creek and equivalent formations should be Tyrannosauridae indet. It's still a fine placeholder name.

 

It's essentially single big theropod syndrome. Regardless of morphology, every megalosaurid from Irhazer is Afrovenator. Every medium and up Yixian theropod is Yutyrannus. All spinosaurid teeth from the Elrhaz is Suchomimus, and everything from the Grès supérieurs is Ichthyovenator.

 

I don't think anyone bats and eye, or really loses sleep over it, until it involves Tyrannosaurus rex. If anything, it's better, you can get all your morphs while they're all the same rarity or value.

 

I don't think it's a huge issue though unless you are calling it something from a different time or deposit.

[BirdsAreDinosaurs]

59 minutes ago, Kikokuryu said:

At the very least, the teeth cannot be attributed to Tyrannosaurus rex regardless. If it doesn't look like T. rex, it simply shouldn't be called T. rex.

 

If Nanotyrannus isn't valid, then all of the Nano teeth from Hell Creek and equivalent formations should be Tyrannosauridae indet. It's still a fine placeholder.

Once it is firmly established that described Nanotyrannus specimens are in fact juvenile T. rex (and most recent studies point in that direction), wouldn't it make sense to assign teeth with the Nanotyrannus morphology to T. rex? Then that is just what juvenile T. rex teeth look like.

Edited October 8, 2023 by BirdsAreDinosaurs

[Kikokuryu]

42 minutes ago, BirdsAreDinosaurs said:

Once it is firmly established that described Nanotyrannus specimens are in fact juvenile T. rex (and most recent studies point in that direction), wouldn't it make sense to assign teeth with the Nanotyrannus morphology to T. rex? Then that is just how juvenile T. rex teeth look like.

No, because we have isolated teeth that fit the description of what a juvenile T. rex tooth should look like. We're talking about really small teeth around the 0.50" range that clearly belong to a large bodied tyrannosaurid, but not 1 to 1 with an adult morph. Ideally with feeding wear to indicated it was being used as unerupted teeth are also a thing.

 

As far as I'm aware of, Nanotyrannus teeth is a case of process of elimination. I don't think there's any good published papers on the holotype that describes the teeth in detail. So it isn't too dissimilar to Yutyrannus that has good (I think?) teeth on the holotype, but really awful description of it.

 

The nano-morphs also get considerably big, up to around 2.5"+ crowns. This was not a "dwarf" theropod by any means. This was a respectable sized tyrannosaurid, perhaps just a bit smaller than the largest Gorgosaurus if we just go by crown sizes. There are also no transitional forms between the nano-morph and rex-morph. The opposite is actually true, the bigger these teeth get, the easier it is to distinguish them. The biggest "Nanotyrannus" teeth are still clearly the same morph as before, not some quasi-rex-nano hybrid tooth.

 

If anything, the nano tyrannosaurid morphs are more similar and harder to distinguish from large dromaeosaurid teeth like Dakotaraptor.

Edited October 8, 2023 by Kikokuryu

[Kikokuryu]

On 10/6/2023 at 1:07 PM, patelinho7 said:

Oh wait yes the proportions are off for tyrannosaur

No, you were right the first time. It almost certainly is a tyrannosaurid.

 

Small tyrannosaurid teeth and larger dromaeosaurid teeth from North America have notoriously similar looking profiles. But the in tooth in question lacks any dromaeosaurid-like characteristics from either Maastrichtian or Campanian deposits. There's no picture of the cross-section, but it appears a bit too robust as well despite the more blade-like morphology.

 

Edit: Also, one thing I don't think anyone mentioned, but the midline serration density for this tooth looks roughly the same on both carinae. If it is indeed Hell Creek, then that should be an immediate red flag for a dromaeosaurid ID. And as @Haravex has already mentioned, what appears to be a slight mesial twist suggest neither of the described dromaeosaurids, Acheroraptor and Dakotaraptor.

Edited October 8, 2023 by Kikokuryu

[BirdsAreDinosaurs]

16 hours ago, Kikokuryu said:

No, because we have isolated teeth that fit the description of what a juvenile T. rex tooth should look like. We're talking about really small teeth around the 0.50" range that clearly belong to a large bodied tyrannosaurid, but not 1 to 1 with an adult morph. Ideally with feeding wear to indicated it was being used as unerupted teeth are also a thing.

 

As far as I'm aware of, Nanotyrannus teeth is a case of process of elimination. I don't think there's any good published papers on the holotype that describes the teeth in detail. So it isn't too dissimilar to Yutyrannus that has good (I think?) teeth on the holotype, but really awful description of it.

 

The nano-morphs also get considerably big, up to around 2.5"+ crowns. This was not a "dwarf" theropod by any means. This was a respectable sized tyrannosaurid, perhaps just a bit smaller than the largest Gorgosaurus if we just go by crown sizes. There are also no transitional forms between the nano-morph and rex-morph. The opposite is actually true, the bigger these teeth get, the easier it is to distinguish them. The biggest "Nanotyrannus" teeth are still clearly the same morph as before, not some quasi-rex-nano hybrid tooth.

Respectfully, I do not think the existence of such isolated teeth is a very convincing argument. Teeth of a single individual do vary significantly in size and shape, depending on the individual and the position in the jaw. Also, Carr argues that size and maturity do not have a strict one on one relationship in T. rex.

 

Also, the original Bakker et al paper on Nanotyrannus does describe the teeth and even has drawings of them showing the relatively narrow and sharp teeth with a pinch at the base. Furthermore, the recent T. rex growth series paper (Carr 2020) includes tooth morphology as one of the characteristics. Here is a quote that might explain the fact there are no intermediates, as the transition is quite "extreme": "The transition from the long and low skull and narrow teeth of juveniles to the tall and powerful skull and thick teeth of subadults occured shortly before the halfway point of life, within a narrow two-year interval between the growth categories."

 

Finally, as far as I know there is no evidence of there being another tyrannosaurid species in those formations. So I would still say that labeling those "Nanomorph" teeth as T. rex makes sense, at least for now.