Hell Creek Dromaeosaurid

[ThePhysicist]

Hi y'all, I picked up this gorgeous Dromaeosaurid tooth. It was listed as Acheroraptor and I bought it thinking it was one. However, upon receiving it and taking some measurements, I believe it may be a candidate for Dakotaraptor steini, as it virtually matches one in @Troodon's collection in every metric. It has a semi-oval base, with no ridges or facets commonly seen on Acheroraptor. The mesial carina is straight, and terminates almost 1/3 the CH from the base.

 

Dromaeosauridae

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

 

CH: ~ 10.5 mm
CBL: ~ 6 mm
CBW: 3 mm
Mesial denticle density: 8 / mm
Distal denticle density: 4.5 / mm

 

 

Distal serrations:

 

Mesial serrations:

 

Base:

 

This is the other tooth I'm referring to:

 

 

 

[Troodon]

Its a Dromaeosaurid given a DSDI of 1.7 with a very short  mesial carina.  The distal denticles are longer than their width so thats good and a CHR at 1.8 is perfect but the base is not oval or almond shape, more of a figure 8 which is not consistent with other teeth I've seen.  Unfortunately we do not have a complete dention of either Acherorapter or Dakotaraptor and our knowledge is based on a few teeth from the holotypes.  I would ID it as DR given we only have one outlier from known teeth.   Hopefully our knowledge of these teeth will continue to grow.   We have no idea if Acherorapter dentary teeth have striations since they are lacking on the holotype so they cannot ever be excluded on these small teeth.

[hadrosauridae]

I've got one of those also!  I didnt realize it could be Dakota.

[ThePhysicist]

3 hours ago, hadrosauridae said:

I've got one of those also!  I didnt realize it could be Dakota.

Can we see it? 

[Gareth_]

I can't offer any help on the ID of the tooth, but that is a stunning example. Perfect condition with really nice serrations 

[Troodon]

Sorry but I slept on this one, had a concern, took another look and will amend my comments and why.

 

Before Acheroraptor was described all these small Dromaeosaurid teeth were called cf Saurornitholestes.  A key characteristics in Saurornitholestes identification is that the apical distal denticles point toward the tip.  I see that in your tooth.  I do not see that characteristic on DR teeth.

 

Again we do not have a complete dentition of either species so we do not know what Acheroraptor dentary teeth look like.  They might not have striations.  Having said all of this given it size there is possibility that this is Acheroraptor or even another Dromaeosaurid.  So since there is no definitive call its best to describe it as indeterminate. 

[hadrosauridae]

9 hours ago, ThePhysicist said:

Can we see it? 

 

OK, here is the best I can offer.  I dont have a microscope and my phone camera is terrible.  The tooth shows a lot of wear to the serrations and it also appears to have some acid etching to the enamel.  Making the detail pics harder is also that the consolidate I used was thicker than it should have been so its obscuring a little bit of detail.  Sadly its missing the majority of its mesial serrations.  The last pic is the best I can get of the mesial.  The serrations are small enough and worn enough that you cant see them without being strongly angled toward the lens which puts it further from the scale and skews the count.  holding it against the card with a loop gets my count of about 8/mm. No apical ridges.

 

crown height is 14mm

base length is 9mm

base width is 4mm

distal serration runs to the base with a density of 4-5/mm

mesial serration is about 1/3 the length with a density about 7-8/mm

Hell Creek fm, Butte Co. South Dakota

 

 

 

 

 

 

 

Edited August 24, 2021 by hadrosauridae

[ThePhysicist]

10 hours ago, Troodon said:

Sorry but I slept on this one, had a concern, took another look and will amend my comments and why.

 

Before Acheroraptor was described all these small Dromaeosaurid teeth were called cf Saurornitholestes.  A key characteristics in Saurornitholestes identification is that the apical distal denticles point toward the tip.  I see that in your tooth.  I do not see that characteristic on DR teeth.

 

Again we do not have a complete dentition of either species so we do not know what Acheroraptor dentary teeth look like.  They might not have striations.  Having said all of this given it size there is possibility that this is Acheroraptor or even another Dromaeosaurid.  So since there is no definitive call its best to describe it as indeterminate. 

Thank you, Frank. I had noticed the leaning of the denticles too but didn't know how they factored in to the ID. I'm certainly not disappointed - it's perhaps my prettiest dino tooth so far. 

 

9 hours ago, hadrosauridae said:

OK, here is the best I can offer.  I dont have a microscope and my phone camera is terrible.  The tooth shows a lot of wear to the serrations and it also appears to have some acid etching to the enamel.  Making the detail pics harder is also that the consolidate I used was thicker than it should have been so its obscuring a little bit of detail.  Sadly its missing the majority of its mesial serrations.  The last pic is the best I can get of the mesial.  The serrations are small enough and worn enough that you cant see them without being strongly angled toward the lens which puts it further from the scale and skews the count.  holding it against the card with a loop gets my count of about 8/mm. No apical ridges.

Looks promising ... @Troodon

[Troodon]

I think this is a Nano tooth.  The mesial serration count is around 4 to 5, midline of the carina which is then a big problem calling this a Dromaeosaurid.  The CHR and CBL are also at the bottom or outside the holotype's numbers for DR.