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Acheroraptor vs Small Nano


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Hi All,

 

Below are 4 teeth w the small (A) tooth being a Acheroraptor w the characteristic changes in size between anterior and posterior carinae serrations and ridges in the crown. I then obtained 3 more teeth (B-D) that are larger (around 13 mms). These teeth do seem to have the serrations size difference in the carinae but only tooth (D) has the ridges and is more flattened while teeth (B) and (C) have no ridges and more thickened. Does the serrations size changes between carinae trump no ridges? And does the thickened size of the two teeth suggests that they are small nano teeth or just different position tooth. Based on the link below by Frank (@Troodon), I would believe they are all acherorpator. Would like to hear you all's thoughts. Thank you.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Apicobasal ridges are diagnostic to Acherorapter so C & B are Nanotyrannus.  Can you provide me a photo of the base and outside edge of D.  Like to see more angled views of the face to better see the ridges.   

 

I recently did a density study of 20 Nanotyrannus teeth in my collection with a CH range of 22 to 50 mm.   You would expect the DSDI to be close to one meaning the distal and mesial density are close.   To my surprise only 5 of those were <=1, all the others were greater, some significantly so the mesial density was greater in most cases.   So to answer your question serration density alone is not a characteristic that alone can identify an Acherorapter tooth.  This study demonstrates that we clearly have two Tyrannosaurid tooth morphologies in the Hell Creek.

 

We really need to look at all the characteristics of an Acherorapter tooth to determine if its one.  Multiple apicobasal ridges are one, DSDI must be greater than one ( holotype: 6.6 to 7.8/mm anterior and 4.4 to 5/mm posterior), posterior denticles are rounded not chisel shape, must be recurved, tooth needs to be very compressed and there should be no twist to the mesial carina.  Identification of Isolated theropod teeth is not a slam dunk.

 

 

 

 

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8 hours ago, Troodon said:

Apicobasal ridges are diagnostic to Acherorapter so C & B are Nanotyrannus.  Can you provide me a photo of the base and outside edge of D.  Like to see more angled views of the face to better see the ridges.   

 

I recently did a density study of 20 Nanotyrannus teeth in my collection with a CH range of 22 to 50 mm.   You would expect the DSDI to be close to one meaning the distal and mesial density are close.   To my surprise only 5 of those were <=1, all the others were greater, some significantly so the mesial density was greater in most cases.   So to answer your question serration density alone is not a characteristic that alone can identify an Acherorapter tooth.  This study demonstrates that we clearly have two Tyrannosaurid tooth morphologies in the Hell Creek.

 

We really need to look at all the characteristics of an Acherorapter tooth to determine if its one.  Multiple apicobasal ridges are one, DSDI must be greater than one ( holotype: 6.6 to 7.8/mm anterior and 4.4 to 5/mm posterior), posterior denticles are rounded not chisel shape, must be recurved, tooth needs to be very compressed and there should be no twist to the mesial carina.  Identification of Isolated theropod teeth is not a slam dunk.

 

 

 

 

Thanks Frank. Unfortunately, I don't have a microscope but upon closer review, I believe that only tooth (D) is an acherorapter. It is the most laterally compressed and does have the ridges. The posterior ridges are absent bc there is natural feeding wear. 

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Reviewing tooth (B), it seems the serrations are the same size. Neither of (B) or (C) has any ridges but tooth (C) does have different serration sizes. So definitely (B) is a juvie nano. Tooth (C) is also?

 

Thanks

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Thanks for the info

B & C are Nano, no ridges, and D does look like Acheroraptor.  Nice teeth 

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1 hour ago, Troodon said:

Thanks for the info

B & C are Nano, no ridges, and D does look like Acheroraptor.  Nice teeth 

Thanks Frank. Appreciate your guidance and willingness to help. Seems I need to get a microscope as my next purchase! 

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