Does This Tooth Tip Serration Looks To Be In T-Rex's Domain?

[AJ Plai]

A while ago I got myself what supposedly is a T-Rex tooth tip, though I have never been able to fully confirm whether if it was really a T-Rex or a Nanotyrannus. I have read about the T-Rex serration count (2 serration or less per mm, if I remember correctly) as a way to help identify a Rex tooth.

Well, I have just managed to find a way to take a pic through a loupe with the tooth tip laying beside a tape measure to get a close-up of its serration. The tooth tip does seem to fit the bill (2 serration / mm) though, I think its probably better to upload the pics and let others with more expertise than me handling these teeth to take a look and share their input & opinions as well, just to be sure in case I may miss something.

Anyway here is what the tooth tip looks like:

And here are the pics of the serration count zoomed up close:

So, does the tooth tip looks to be a T-Rex from the look of it?

Thx in advance guys

[jpc]

can we see a cross section of the broken surface?

[Troodon]

The serration shape and size are classic T Rex. The tip also looks Rex.

[AJ Plai]

can we see a cross section of the broken surface?

Certainly:

And really good to hear some positive confirmation from you, Troodon

Thx.

[Regg Cato]

Yup I'd have to agree this is from Tyrannosaurus rex.

[Boesse]

There are a large number of vertebrate paleontologists who operate under the well-supported hypothesis that Nanotyrannus is a juvenile T. rex, so your question is probably moot anyway.

[Troodon]

I enjoy the debate. However, I had the opportunity to have a discussion with Phil Currie who is the most prominent paleontologist on theropod dinosaurs in the world and he views Nanotyrannus as a valid species. I also had an opportunity to see, first hand, a complete adult specimen an I have a hard time to see how it would morph into a Rex.

[Regg Cato]

There are a lot of ontogenetically advanced features observable in Nanotyrannus, and given its small size it's certainly reasonable to assume it would have had a different ecological niche from Tyrannosaurus, but I haven't personally seen any of the material so I can't make a concrete statement myself lol.

[jpc]

I enjoy the debate. However, I had the opportunity to have a discussion with Phil Currie who is the most prominent paleontologist on theropod dinosaurs in the world and he views Nanotyrannus as a valid species. I also had an opportunity to see, first hand, a complete adult specimen an I have a hard time to see how it would morph into a Rex.

I'm still undecided about T rex and Nanno, but I think it can also be hard to see how a baby human skull can morph into an adult human skull... but they do.

[AJ Plai]

Out of curiosity, it seems looking at a tooth's cross-section is another way of identifying a potential T-Rex tooth - what features exactly do you have to look for in the tooth's cross-section to know if its a T-Rex or not, other than trying to see if the tooth is fat with a round oval rather than flat bladed in shape, that is?

Edited April 9, 2013 by AJ Plai

[Troodon]

Excluding Pre-max teeth most Rex teeth tend to be oval in shape. You do not see that in Nano teeth which are compressed or flatter in shape.

[Opisthotriton]

Funny thing is, juvenile T. rex teeth are also compressed or flatter in shape...

[Troodon]

Well okay. I just have to look at my collection which has close to 20 Rex teeth in it with crowns from 1/4" to just shy of 6". All have big serrations and are oval in shape. My nano teeth are compressed with finer serrations. My recommendation to anyone wanting to purchasing a Rex tooth is that it should scream Rex and not get into a Nano or Rex debate. You will be happier in the long run and enjoy a super specimen that no one will question.

[Down under fossil hunter]

It does look like a Rex tooth to me.

I agree with Troodon that if you are in the market then you should spend the extra and get a genuine big, fat, Rex tooth. lol

[Down under fossil hunter]

Well okay. I just have to look at my collection which has close to 20 Rex teeth in it with crowns from 1/4" to just shy of 6".

Can we see some pics of your best ones pleeeaase!

[Troodon]

No problem Down Under here are three that I have pictures available : the Pre-Max is 2 7/8 inches (Hell Creek Fm, South Dakota) and as large as they get, the rooted Posterior is 3 inches (Hell Creek Fm, Montana) and the Maxillary tooth is 3 1/2 inches (Lance Fm, Wyoming).

[AJ Plai]

Awesome teeth you have there! And in very good condition too! Were these from personal find or purchase?

Thx for sharing

[Troodon]

Of the three teeth shown I purchased the pre-max about 15 years ago. Here are some more of my rex teeth and I've included a couple of juvenile teeth so that you can see that even at that size they are rex. The first two images are my largest at just shy of 6 inches (15 cm) from montana. I left the big crown on the matrix. The next two are some of smaller teeth also from montana and the first one is 5 cm with the crown at 1.2 cm, the last tooth is 1.5 cm.

[donckey]

Hi Plai and others,

I also have a tooth of which I hope it is a T-rex.

A few weeks ago there was a nice item about how to identify rex from other T-species.

He posted a link to internet with advice how to ID one.

Focussing only on the serrations the following was said:

about 30 serrations / cm, Nanotyrannus

about 25 serrations / cm, Albertosaurus and Daspletosaurus

12 - 20 serrations / cm, Probably T.rex

To be honest, I do not know how serrations are counted, so I posted two pictures.

Hope somebody can tell me how many serrations/cm (about 11 or about 22? )

I also hope somebody can give me an estimate of the serrations/cm of a Carcharodontosaurus (N.Africa).

Seeing Plai's pictures, I do not now if you used cm (mm) But the way I think serrations must be counted I would say the tooth has about 30 serrations / cm,

so, according to the paper I read, should fall in the Nanosaurus range and is not even close to a T-rex.

Still the most of those reacting in this topic seem to be sure about the T-rex ID.

Peter

[Troodon]

Peter you can read either mm or cm the results should be the same but cm can be a bit more accurate since you are looking at a wider group. In you pictures if those are mm lines it would read around 11 serrations per cm which would be in the T Rex range. I do not have the info you are asking on a Carcharodontosaurus but if you have one just follow the same process and see what you get.

[32fordboy]

I can't make any good comments regarding the tooth's ID, but spoke with Pete Larson at the Denver Show last September and he has some really convincing reasons why Nanotyrannus is a valid genus. He said he's absolutely convinced it is a valid genus, as am I after our conversation.

On an interesting side note, I think the baby Tarbosaurus skeleton is of great importance for the "Nano vs juvenile rex" debate. Also, count me in the camp that believes Tarbosaurus bataar should be Tyrannosaurus bataar, though more educated types can argue that one.

[Regg Cato]

There was a recent paper that made a convincing case for separating Tarbosaurus and Tyrannosaurus; but frankly Late Cretaceous North America and Asia shared so many similar taxa that it becomes a situation where you have to decide where to draw the line. Saurolophus is present in both North America and Asia, and so far nobody's suggested creating a new genus for either species. Prenocephale is present in both North America and Asia, though Williamson and Carr (among others) favor calling the North American material Sphaerotholus and Schott wants to call some of it "Foraminacephale." There are a lot of similarities between Velociraptor and Dromaeosaurus, but so far nobody has suggested subsuming Velociraptor. Parasaurolophus is present in both North America and Asia, though nobody has proposed subsuming Charonosaurus with it yet. Troodon and Sauronithoides are very similar.

With a couple of these taxa there are valid reasons for keeping the North American and Asian species in distinct genera, but NA and Asia share a lot of Late Cretaceous genera. Another interesting situation is that North America has two major faunal zones (one concentrated around Alberta and Montana and one focused around New Mexico) each with their own distinct array of species, some of which have been separated into new genera. Stegoceras validum is present in Alberta, while Stegoceras novomexicanum is from New Mexico. Parasaurolophus walkeri and Parasaurolophus tubicen, Prenocephale edmontonensis and P. goodwini, Prosaurolophus maximus and P. atopus (Lophorothon)...the south has their own menagerie of bizarre Ceratopsians too, starting as far north as Utah.

[32fordboy]

Dinosaurs are kind of odd that way...they seem to have been successful enough that evolution was relatively slow (think crocodiles)...at least for advanced theropods. I just try to think on the scale of mammals. What makes one genus different from another? Bison are a good example. All the same genus, totally different animals, and they spanned most of the planet. Some have even suggested that Bos and Bison are the same...which seems astonishingly crazy (though they can successfully breed, as indicated by the fact that only 4 Bison herds have not been mixed with cattle). Then you have humans. Totally different skeletal proportions, but they are all grouped Homo...incidentally, that genus spans the entire planet, as has Panthera (all very similar animals within that genus, despite the striking differences in attitude...tigers are supposedly far more aggressive than lions...and coloration and manes). Still, I feel there's a point when common sense beats "what the science says."

Obviously, that's a 3rd-view-uneducated perspective based on mammals, but it all boils down to knowing where to draw the line, just as you said. As is often asked, what's in a name?

Of course, the fossil world is so over-split, anyhow. Excellent post, Regg. I'll have to find that paper.

[Down under fossil hunter]

Of the three teeth shown I purchased the pre-max about 15 years ago. Here are some more of my rex teeth and I've included a couple of juvenile teeth so that you can see that even at that size they are rex. The first two images are my largest at just shy of 6 inches (15 cm) from montana. I left the big crown on the matrix. The next two are some of smaller teeth also from montana and the first one is 5 cm with the crown at 1.2 cm, the last tooth is 1.5 cm.

Trexrootedpremax.jpgTrexlarge.jpgTrexrootedjuvie.jpgTrexjuvie.jpg

Amazing collection there Troodon, I am very envious of the spectacular teeth in your collection, well done!

[Regg Cato]

Dinosaurs are kind of odd that way...they seem to have been successful enough that evolution was relatively slow (think crocodiles)...at least for advanced theropods. I just try to think on the scale of mammals. What makes one genus different from another? Bison are a good example. All the same genus, totally different animals, and they spanned most of the planet. Some have even suggested that Bos and Bison are the same...which seems astonishingly crazy (though they can successfully breed, as indicated by the fact that only 4 Bison herds have not been mixed with cattle). Then you have humans. Totally different skeletal proportions, but they are all grouped Homo...incidentally, that genus spans the entire planet, as has Panthera (all very similar animals within that genus, despite the striking differences in attitude...tigers are supposedly far more aggressive than lions...and coloration and manes). Still, I feel there's a point when common sense beats "what the science says."

Obviously, that's a 3rd-view-uneducated perspective based on mammals, but it all boils down to knowing where to draw the line, just as you said. As is often asked, what's in a name?

Of course, the fossil world is so over-split, anyhow. Excellent post, Regg. I'll have to find that paper.

Very true, and as one who's grown up with Dinosaur-based taxonomic standards, mammal taxonomy seems a bit strange to me lol. Each group seems to have its own set of standards; if we tried to apply insect taxonomic procedures to dinosaurs, for example, all large ornithopods would be called Iguanodon (and that genus would have about 40 species lol). I mentioned some of my conclusions regarding Pachycephalosaur speciation in my blog, but in all honesty what it comes down to is the fact that the "genus" has lost much phylogenetic usefulness and now seems to be an arbitrary method of grouping species. What "level" of characters constitutes a genus is somwhat subjective, because you can find within a group of species any number of synapomorphies, but interpretations of the number of genera represented differ. As an example, with Tyrannosaurs, you could recognize Nanotyrannus, Albertosaurus, Daspletosaurus, Tarbosaurus, Appalachiosaurus, Tyrannosaurus, Shanshanosaurus, Bistahieversor, and Gorgosaurus as valid genera; that's 9 genera. However, it really isn't that far of a stretch to say that those species could be assigned to just 2 or 3 genera (I've seen it done; just ask Greg Paul lol).

Anywho, now that I've completely derailed the topic lol......