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The_bro87

Campanian tyrannosaurs

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The_bro87

I have 2 campanian tyrannosaur fossils, one from the Judith river formation from Blaine county in Montana, and another where the only locality I know of is that’s from the two medicine formation. I was wondering if the locality can help determine between Gorgosaurus, Daspletosaurus and Albertosaurus, or if any formations are limited as to which species is present.

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The_bro87

Also the reason I posted this was because I thought I remembered reading somewhere that the two medicine formation was limited to Gorgosaurus and Daspletosaurus, and that only Albertosaurus has been found in the Judith river formation so far. I wasn’t sure if there was any validity to this 

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Troodon

There are no Tyrannosaurids described from the JRF.  Unlikely its Albertosaurus since its found in younger deposits of the Horseshoe Canyon Fm., AB.  Either cf Gorgosaurus or cf Daspletosaurus 

 

Ditto Two Medicine FM.  A Daspletosaurus hornei is described from there and a Gorgosaurus sp.

 

 

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The_bro87

Does that completely rule out Albertosaurus? I understand a 100% accurate ID isn’t possible, but is there even a possibility that Albertosaurus is present? Also that’s Interesting. I always thought Alberotsaurus was the most common if the three, and that most tyrannosaur teeth from those formations were most likely Albertosaurus. I wonder why I thought that 

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Troodon

Yes for now..Based on the current understanding only Daspletosaurus and Gorgosaurus are known in Campanian deposits.  Albertosaurus has only been described from the very late Campanian and early Maastrichtian deposits of the HCF.  They are stratigraphically separate.  Our understanding of these tyrannosaurids continues to change based on discoveries and that's what theropod paleontologists like Phil Currie are publishing.  

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The_bro87

Huh, that’s pretty cool. I never new that Albertosaurus could be found in Hell Creek deposits. Thank you for all this info I never knew the complexity of where tyrannosaurs can be found 

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Troodon

No it's only found in early Maastrichtian deposits of the HCF.  Hell Creek is in younger Maastrichtian deposits so it's not there. HC that's Horseshoe Canyon my bad

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The_bro87

Oh that’s a relief! I was worried there’s a chance that any potential rex teeth I was looking at from the Hell Creek formation also had to be distinguished from Albertosaurus and Nanotyrannus. Thanks still

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PaleoNoel
1 hour ago, The_bro87 said:

Oh that’s a relief! I was worried there’s a chance that any potential rex teeth I was looking at from the Hell Creek formation also had to be distinguished from Albertosaurus and Nanotyrannus. Thanks still

To clear up any confusion, when he says HCF he meant the aforementioned Horseshoe Canyon Formation in Alberta which is late Campanian, early Maastrichtian rather than the mid to late maastrichtian hell creek formation of MT, SD and ND (which would have the same acronym). Additionally, when the genus Albertosaurus has been used to describe teeth from the JRF it is generally under the idea that Gorgosaurus and Albertosaurus were the same genus (A. sarcophagus from Horseshoe canyon and G. libratus from older Campanian deposits in MT and Alberta). 

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The_bro87

That makes more sense thank you 

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