Texas Dinosaur Finger/Toe Bone?

[GPayton]

Hey everybody, it's been a while! I wanted to ask you all your opinions on this strange bone I found in North Texas a few weeks ago. I was hunting at a creek that cuts through the Eagle Ford - Austin Chalk contact and produces shark teeth and oysters identical to Post Oak Creek in Sherman. This bone was found in gravel in the creek bed downstream of the contact zone so there's unfortunately not much I can do to narrow down what formation or member it may have actually come from (although the preservation does seem to have more in common with bones from the chalk). 

The bone is heavily eroded and at least half is missing with the inner cavity having been infilled with matrix that still protrudes and suggests what the original shape/length of the bone might have been. One articular facet is well-preserved. 

My first thought was that this would have to be some sort of marine reptile phalanx but after doing some research I could find nothing that looked similar: the articular surface of this bone is concave and squared off with right angles on each edge whereas the same surface on mosasaur, turtle, and plesiosaur phalanges is circular and flat. 

I met up with @Jared C a week later for a fossil hunt in Austin and he passed along pictures of the mystery bone to Prof. Polcyn at SMU who agreed that it does not look like it came from a marine reptile and actually believes it may be dinosaur. Up until that point I hadn't even considered dinosaur as an option. Obviously finding any dinosaur material in Texas (outside of the Big Bend area) is extraordinarily rare and my find would be even rarer as it originated in marine sediments deposited during the late Turonian to Coniacian , a time when almost nothing is known of North American dinosaurs from the eastern half of the continent. 

I compared the phalanx to different dinosaur phalanges and I feel like if it is in fact dinosaur than I can rule out anything quadrupedal like hadrosaurs or nodosaurs as it isn't bulky enough and the infilled matrix indicates a very hollow interior. Right now my best guess is ornithomimid or theropod but I am very open to being proven wrong if I'm way off the mark here. In particular, the groove in the center of the articular facet is throwing me for a loop; on all the bipedal dinosaur phalanges I've seen, both manual and pedal, there is a ridge instead of a groove in that exact spot on the facet. 

Any help on an ID is greatly appreciated! If anyone reading this knows of any dinosaur experts here on the forum, feel free to tag/link them down below so they can take a look. 

@hadrosauridae@ThePhysicist

 

 

Edited September 3 by GPayton

[CDiggs]

46 minutes ago, GPayton said:

 

There isn't any chance of Pleistocene material in the area is there? Good chance it's another case of a hammer wanting everything to be a nail but that groove looks to me like where a mammal proximal phalanx articulates with a metapodial. I could easily be totally wrong though.

 

[GPayton]

I definitely had the same idea at first (even down to looking up Harry's deer phalange pictures too for comparison! ) and I have found some bits and pieces of Pleistocene mammal material in this creek before, but I don't think that degree of fine-grained matrix infilling in the bone cavity and the cancellous structure is possible in something as young as Pleistocene. I did also find a mosasaur and a Xiphactinus vertebra the same day and they had identical preservation which is what's leading me to believe it's Cretaceous. 

[hadrosauridae]

Head scratcher!  I think the deer bone ID is due to the straight-on end view is deceiving. It looks like 2 grooves, but the other pictures show is a "V" shape into the center line, which rules out the deer.  The fossilization is pretty wild, I've never seen a center like that, inside of obvious outer bone material.   Sorry I cant help with an ID

[ThePhysicist]

Definitely interesting, but hard for me to say anything with certainty; find a whole one next time, please 

 

I'm having trouble thinking of alternatives to dinosaur, especially since it appears to be hollow - that alone disfavors a marine reptile. Try reaching out to a few more professionals.