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Troodon

Identifying Theropod Teeth from the Hell Creek/Lance Fm

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bcfossilcollector

Regarding Pectinodon bakkeri I've observed illustrations of the teeth such as the image you've provided that suggest the tip of the tooth was rounded certainly by comparison to Troodon formosus. However the few photos I've found and the one specimen I've observed under magnification, of teeth attributed to Pectinodon, suggest a much finer tip. These teeth had large denticles only on the posterior edge of the tooth. Could this be explained by a variation in tooth morphology as is sometimes observed in other theropods? Or perhaps the teeth were misidentified although the absence of the Troodon type denticles from anterior portion of the tooth would suggest not? Any information you can provide would be appreciated and I thank you again for the valuable information you always provide!

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Troodon

Good question. I've see both types and Ive attached a picture of each from my collection. Hope that's what you were referring to. I don't know if we are looking at positional variation or tooth morphology. The troodon maxilla I provided the ROM was their first look at any North American troodon tooth in a jaw so I have to believe little is know about T. pectinodon teeth.

Sorry for the poor quality images just used my phone. I should add the other image to my post.

post-10935-0-91961000-1454727265_thumb.jpgpost-10935-0-36442700-1454797208_thumb.jpgpost-10935-0-23203700-1454797213_thumb.jpg

Edited by Troodon

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bcfossilcollector

It is what I was referring to. I can see it in the two pictures provided. It's an excellent comparison. Another fascinating dinosaur and I guess mystery to ponder.

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hxmendoza

Troodon, I'd like to add a correction if I may. The description for Paronychodon is correct, but the illustration provided is not.

True Paronychodon lacustris teeth do not have any serration denticles.

The illustrated tooth is actually Zapsalis abradens. These teeth are wider for to aft and have serrations on the distal/posterior edge and none on the medial/anterior edge.

Edited by hxmendoza

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Troodon

That image came out of Dinosaur Systematics which was published in the early 90s. Agreed in 2013 that image was described to Z. abradens but only from the Judith River Fm. although there are affinities to those found in the Hell Creek. Like Paronychodon and R. Isoceles these tooth taxons are highly debatable and most will change when the research is concluded on the jaw that contains both morphologies. Thanks for the pickup.

Attached, not the sharpest images but you can see the different morphologies of these teeth from the Hell Creek.

cf Z.abradens

post-10935-0-55514400-1455624463_thumb.jpg

cf Paronychodon

post-10935-0-61975300-1455624499_thumb.jpgpost-10935-0-56813300-1455624579_thumb.jpg

Edited by Troodon

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hxmendoza

Troodon, your two lower images are correctly true, non-serrated, cf. Paronychodon sp. teeth (at least until your jaw is described).

I have to disagree on you with your cf. Zapsalis tooth photo. That tooth is actually an anterior tooth (probably premaxillary) of Pectinodon bakkeri. Nick Longrich and I have discussed these teeth at length. Those denticles are far too large for Zapsalis. They are comb shaped and sharp. Zapsalis denticles are smaller and more box-like or chisel shaped with somewhat rounded tips.

Anterior and premaxillary teeth of Pectinodon do have varying degrees of vertical striations also. The tip of Pectinodon teeth actually becomes inclusive as being the first large denticle of the posterior edge, as we can see represented in your pictured tooth. This is also a distinguishing feature that separates Pectinodon from the cf. Troodon formosus teeth that are also found in the Hell Creek (though true Troodon formosus is only from the JRF).

The anterior Pectinodon teeth also can sometimes have subtle crenulations or rippling that appear to be failed denticles on the anterior/mesial carina of the tooth. This is evident also on your pictured tooth.

Zapsalis teeth have only a naked smooth anterior/mesial carina. Zapsalis teeth are also noticeably larger in size than Pectinodon teeth.

Attached is the page showing Pectinodon teeth from Longrich's paper on it. Your tooth resembles the first two illustrated teeth.

post-7726-0-43091800-1455636694_thumb.png

The next photos are of my true, cf. Zapsalis sp. tooth. This one is from the Hell Creek Formation. It is 16mm tall. Note the difference in denticle size and morphology.

post-7726-0-25147700-1455637097_thumb.jpegpost-7726-0-55365800-1455637066_thumb.jpegpost-7726-0-04986300-1455637140_thumb.jpegpost-7726-0-40556900-1455637168_thumb.png

Edited by hxmendoza

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Troodon

Your correct. I initially thought that tooth was 1/2 inch. When I went looking for it it turned out to be 5mm and has to be Pect. Thanks for the correct image

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hxmendoza

Your correct. I initially thought that tooth was 1/2 inch. When I went looking for it it turned out to be 5mm and has to be Pect. Thanks for the correct image

You're very welcome.

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Killclaw

Gentleman your opinion please on this tooth I own, would you identify as Troodon genus? Length is 11.2 mm, some worn serrations on the outer edge, thank you....

38049.jpg

Edited by Killclaw

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Troodon

Yes definitely Troodon. The worn serrations are pretty typical.

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-Andy-

To contribute, here I have a Hell Creek tooth from Carter County of Montana. It's 2.62 inches in a straight line, bigger than some T-Rex teeth out there, yet its features remain distinctly Nanotyrannus.

post-4888-0-63927200-1455798132_thumb.jpg post-4888-0-16195800-1455798138_thumb.jpg post-4888-0-19966500-1455798142_thumb.jpg post-4888-0-14960600-1455798321_thumb.jpg

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Troodon

Andy thanks for sharing that beautiful tooth and it's partially rooted. Good example of a specimen at the high end of range for Nano teeth. Let's me add that Pete Larsen of the BHI agreed with the ID.

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MarcNL

WoW great info, thanx!

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Troodon

Updated the initial page to reflect the troodonitid genus change and added additional images and information.

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jpc

troodon... I have not seen the news on a genus change within the troodons.  Can you enlighten me and others?  Thanks. 

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jpc

Thanks, troodon.  That Canadian paper is firewalled.  

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