Rex?

[Dino Dad 81]

Thanks for all the ID help lately. I've got another that's interesting to me, if you've got time.

• From the hell creek formation, Garfield Co, Montana
• CH: 12.1mm
• CBL: 4.6mm
• CBW: 3.0mm
• Mesial serration density: smooth, but curious to see if you perceive signs of worn denticles
• Distal serration density: about 4.33/mm
• Serration shape: tyrant or something else worn down??
• Base cross-section: Oval--almost round
• Mesial carina: Hard to say if straight. Sort of seems straight but very offset from center.

 

 

 

 

 

 

 

 

 

Almost looks like worn denticles here:

 

 

 

 

[jpc]

@troodon is our local expert on these things, but I think it is too curved and thin to be a tyrannosaur.  In focus pictures are always a better way to get good answers.  

 

 

[Dino Dad 81]

Yeah, it's smaller than it looks in these pics (a lot of zoom), but I can try for better pics with a tripod if there isn't diagnostic info for Troodon to get a feel from. I considered a dromie indet premax at one point (if mesial carina is naturally smooth), but, unlike the lateral teeth, I believe those have a hefty mesial twist.

Edited May 26, 2022 by Dino Dad 81

[Troodon]

I think its a Tyrannosaurid definitely not a Dromaeosaurid with a serration Density ratio of close to 1, mesial twist and denticles that look chisel.   Its also a process of elimination not sure what else it could be.

The recurve is a bit much but here is one at 1 1/4" that looks similar just larger

[Dino Dad 81]

@Troodon dromie wasn't so much on my radar here. My main question is whether you lean REX within tyrannosaurid. To me, the base just looks too round for nano:

 

 

 

Here's a different tooth with a similar degree of recurve, but a narrower base (i.e., more likely nano). and even this base is rounder than typical nano:

 

 

 

 

[Troodon]

Could be a Nano maxillary but will need for this animal to grow a bit older and see how the tooth might become more diagnostic   Why I called it a tyrannosaurid.  

[Nanotyrannus35]

It does however have a bit of a pinch in the middle of the tooth though, so it could be nano.

[Dino Dad 81]

(I ran on to add this, but you beat me to it with the response.)

I just glanced down at it and it happened to be in this odd angle, which I think has that unique Rex maxillary taper/shape. Another testament to the base being rounder than any nano I've seen. Again, I came on to share this and figured I still would--but I don't mean to "push".

 

 

Edited May 26, 2022 by Dino Dad 81

[Dino Dad 81]

From a cast I have:

 

 

[Troodon]

Thats a Trex not Nano.  Yours is not round or oval.

[Dino Dad 81]

@Troodon Not sure which one you're referring to--I've posted a known nano and a rex cast--just to make sure we're talking about the same one, this is the one I'm posting about (apologies if that was already clear):

 

 

 

[Dino Dad 81]

I'd be grateful if I could just get confirmation that we're not mixing/matching pics from the several teeth posted (some of which were posted for nanotyrannus examples to see the contrast).

To be clear, I'm investigating the one in the post directly above. It has CBR of about 0.67, which just seems very unusually high/round for a nano--my impression is that only a freak nano goes much above 0.6 and they tend to be around 0.5, whereas Rex tends to be around 0.7.

 

@Troodon If, after confirming we're talking about this same tooth, Rex still doesn't seem like the stronger possibility, I promise to have no further comments :-)

[Troodon]

On 5/26/2022 at 10:06 AM, Troodon said:

Could be a Nano maxillary but will need for this animal to grow a bit older and see how the tooth might become more diagnostic   Why I called it a tyrannosaurid.  

Let me restate it.  Its definitely not oval or round.

[Dino Dad 81]

Thanks, Frank! Enjoying this tooth enough that I just wanted to be sure we were on the same page.