Unknown Theropod Toe Bones

[Norki]

Hello,

 

I surface collected these two associated and sequential toe bones from the Horseshoe Canyon formation, but can't quite get a definitive ID on them. After a bit of research they appear to correspond most closely with Albertosaurus, but I hope to get a second or third opinion before I label them. I know that theropod toe bones can be tricky, but I'm hoping that the claw has some diagnostic features.

 

Thanks!

 

Bone 1:

 

 

 

 

Bone 2:

 

 

 

 

 

 

Edited July 6, 2021 by Norki

[Troodon]

Nice find.  I dont see a Tyrannosaurid in either specimen.   Can you post a photo of  ventral and dorsal view of the claw. 

[Norki]

On 7/5/2021 at 8:17 PM, Troodon said:

Nice find.  I dont see a Tyrannosaurid in either specimen.   Can you post a photo of  ventral and dorsal view of the claw. 

[Troodon]

Thanks, My best call that its one of the Caenagnathid's from HCF.

[Norki]

19 hours ago, Troodon said:

Thanks, My best call that its one of the Caenagnathid's from HCF.

Thanks! One last thing - near as you can tell, are these two bones arranged correctly in sequence, and can you tell which digit they're from?

Edited July 10, 2021 by Norki

[Troodon]

I doubt it, distal end of phalanx looks awfully wide compared to claw.

[Norki]

On 7/10/2021 at 1:39 PM, Troodon said:

I doubt it, distal end of phalanx looks awfully wide compared to claw.

Sorry to bug you about this again, but I'm having trouble finding references of caenagnathid feet from the HCF to determine which specific phalanges these are... The best reference I could find for a caenagnathid foot was actually this Anzu foot that you posted from your own collection, so I'm wondering if you could provide your best guess for these digits' positions.



I agree with you that the claw is far too thin for these to have likely been in sequence, but after having looked at this Anzu foot and a few other basic illustrations of caenagnathid feet online, it still seems to me like the most likely fit for these two bones are Digit IV, 4 & 5, based on their general morphology. How much variability is there within caenagnathid feet, anyway? Do you know of any resources that could help me with narrowing this down?

Edited July 20, 2021 by Norki

[Troodon]

I dont think you will find anthing published on these feet.  I used lots of photos from the BHI to give me clues.

Your phalanx is the one before the claw so Digit IV phalanx 4 might fit.   Not sure on the claw could be Digit I

[hxmendoza]

Hi. The claw is definitely a Tyrannosaurid hallux claw from the left foot. So Left D-I-2.

the tell tale feature is the oval articulating end. Also in Tyrannosaur hallux claws the lateral blood groove is more pronounced and developed than the one on the medial side. Also the lateral groove is higher up on the claw that the medial one. All of these features are present on your claw. Have seen, worked on, and owned a few of these including ones from Tarbosaurus. There is variation in the flexor area, stoutness, and length within these tyrannosaurid hallux claws, but the main features are consistent. 
 

Being as only Albertosaurus sarcophagus is present in the Horseshoe Canyon Formation  (at least until a Daspletosaurus is eventually reported, if ever) this hallux claw can be assigned to that genus and species.

 

The phalanx is more problematic, but I would agree that for now it’s best to tentatively assign it to a Caenagnathid.

 

Hope that helps.