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Hi y'all, got this small theropod in the mail; I bought it suspecting it was Tyrannosaurid. Upon in-hand inspection, I believe that suspicion is confirmed. It bears close resemblance to one of my larger juvenile T. rex maxillary teeth. It also appears to have a slight pathology near the apex - a slight bend.  @Troodon

 

Tyrannosauridae

Hell Creek Fm., Wibaux Co., MT, USA

CH: 9 mm

Mesial serration density: ~ 5.3 / mm

Distal serration density: ~ 5 / mm

 

668250705_IMG_27222.thumb.jpeg.fbb95f8d9e41abeda84aa36711880e96.jpeg

IMG_2725.thumb.jpeg.3fc028bc9d2a8c8ae3ad7b355934cab6.jpeg

 

Serration densities:

IMG_3467.thumb.JPG.ecd9ba9c6e078722aef5bb8a7a3999ac.JPG

IMG_3468.thumb.JPG.f16553c42a98aaad8e2eef35488458e5.JPG

 

Serrations:

IMG_3473.thumb.JPG.a842f10cc3b2c0137ba2696d9753e9f1.JPG

 

IMG_3476.thumb.JPG.f133a738ba29f838792d7fd41d7dca8c.JPG

 

IMG_3478.thumb.JPG.4bcc8b0d52e75443eaea664bef30b5e7.JPG

 

IMG_3477.thumb.JPG.c2446600f316890dd7b0c02f36ed0020.JPG

 

Here the pathology is more evident:

IMG_3470.thumb.JPG.d921f9608da0edb023cba73790f245be.JPGIMG_3472.thumb.JPG.bc5a4c209e6775379a1baadd494fa352.JPG

 

Base (comparison with other T. rex maxillary tooth, right):

IMG_3469.thumb.JPG.1e5e5402e79251e681296c102398f9aa.JPGIMG_1071.thumb.jpeg.938a6a247768cd714332959c70a76f6b.jpeg

 

Edited by ThePhysicist
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  • ThePhysicist changed the title to Infant Hell Creek Tyrannosaurid?

Looks like a Tyrannosaurid.  Not sure you can positively call it infant could be a replacement tooth.

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The hatchling Tyrannosaurus material reported earlier this year is quite a bit smaller than this. So juvenile for sure but not hatchling.

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2 hours ago, Troodon said:

Looks like a Tyrannosaurid.  Not sure you can positively call it infant could be a replacement tooth.

The reason I believed it was a functional tooth was due to potential evidence of wear on the mesial side of the tip (which wasn't in focus in the previous images):

 

IMG_3494.thumb.JPG.9e6c87c358aa2f3bc7bd545ea23f0b1a.JPG

IMG_3497.thumb.JPG.8fe3f9157b537e1a38ed454db67b2843.JPG

IMG_3495.thumb.JPG.1442cc1002cc86eda081098f2418ecd1.JPG

 

56 minutes ago, jdp said:

The hatchling Tyrannosaurus material reported earlier this year is quite a bit smaller than this. So juvenile for sure but not hatchling.

I'm assuming you're referring to the embryonic Daspletosaurus dentary? (https://www.researchgate.net/publication/348756036) Good point, "juvenile" is probably more accurate. However, in the same paper they refer to this comparably-sized Tyrannosaurid premax as "perinatal:"

1482071248_ScreenShot2021-10-13at12_21_00AM.thumb.png.26abaf3871e7d23737964c3c2020d239.png

I don't want to get into semantics too much, but if there are more concrete definitions, I'd be happy to learn.

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I always struggle with age classification of isolated material especially teeth because of unerupted teeth and heterodonty.   Can be very subjective if there are not clear features pointing one way or another..

Anyway David Hone et al put this out in 2016 to help understand age terms.  I am an "old adult" :)

Screenshot_20211013-032530_Firefox.thumb.jpg.3176ee68e7cbed8155ed0c009158d166.jpg

 

https://doi.org/10.1098/rsbl.2015.0947

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Nice specimen and excellent photos! :)

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8 hours ago, ThePhysicist said:

I'm assuming you're referring to the embryonic Daspletosaurus dentary? (https://www.researchgate.net/publication/348756036) Good point, "juvenile" is probably more accurate. However, in the same paper they refer to this comparably-sized Tyrannosaurid premax as "perinatal:"

1482071248_ScreenShot2021-10-13at12_21_00AM.thumb.png.26abaf3871e7d23737964c3c2020d239.png

I don't want to get into semantics too much, but if there are more concrete definitions, I'd be happy to learn.

 

I dunno about the premaxillary tooth, but I did the first pass CT scan of the dentary for Greg and Amber and those teeth are absolutely tiny. Ostensibly that jaw might be something besides tyrannosaurid I suppose; I'm not a dinosaur expert by any means.

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13 hours ago, jdp said:

 

I dunno about the premaxillary tooth, but I did the first pass CT scan of the dentary for Greg and Amber and those teeth are absolutely tiny. Ostensibly that jaw might be something besides tyrannosaurid I suppose; I'm not a dinosaur expert by any means.

Oh wow, that's cool! 

 

There's also this juvenile Tarbosaurus which was a similarly-sized Tyrannsaur, and I assume they probably had a similar early-stage growth curve (as the N. American Tyrannosaurs do), so a comparison might be useful to place loose constraints on age.

 

315847422_ScreenShot2021-10-13at4_17_36PM.thumb.png.4e062d5b717c09b821049ac31d839169.png

1964624280_ScreenShot2021-10-13at4_18_03PM.thumb.png.b3bdc0479a97003b9be7b43b9026f8de.png

https://doi.org/10.1080/02724634.2011.557116

 

In the paper, they estimate the age of the individual to be 2-3 years. So if this is juvenile, then it might be in that ballpark.

 

On 10/12/2021 at 9:42 PM, Troodon said:

Looks like a Tyrannosaurid.  Not sure you can positively call it infant could be a replacement tooth.

I thought about replacement teeth a bit. It seems odd to me that germ crowns would be significantly smaller than the the one they're replacing and have an enamel coating. I would think that replacement crowns would grow to a similar size before getting an enamel coating, otherwise the enamel has to be continually destroyed and replaced as the tooth grows, which seems inefficient. I found this paper which discusses tooth development: https://doi.org/10.1080/08912963.2019.1675052 but would appreciate other references.

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