Pathological Proximal Tibia?

[CDiggs]

Hi Fossil Forum!

 

This past Monday I was searching my favorite gravel bar in SE Texas and I came up with some pretty great finds including my first ever ground sloth claw core but there was one object that has me and a few other people scratching our heads. I'm assuming that along with all of the other identifiable bone fragments I've found at this spot that this dates to the Pleistocene but there is Cretaceous invertebrate material and petrified wood that possibly date from the Eocene through the Pleistocene that I've found here as well.

 

On to the mystery object! This articular surface just screams proximal tibia at me but I'm not satisfied with any matches I've tried to make to Camel, Bison, Horse etc. however there is a fair bit of damage along the edges so maybe I won't be able to nail down a species. I would at least like to confirm the element if possible and maybe narrow it down to family or genus.

(oh and the scale just says metric but I'd hope it's obvious that the scale is in CM)

 

It's the diaphysis that really leaves me and others confused and thinking possibly pathological because this doesn't look right at all for a tibia, at least not any that I've seen before!

 

 

 

 

Apologies for the horrible focus on some of these images (especially the last one), the three dimensionality of this piece has been giving me some trouble when attempting to photograph it.

 

I would really appreciate any thoughts y'all might have on this one!

 

Thanks,

Cdiggs

[Harry Pristis]

I think you have the fused tibia-fibula symphysis along with the fibula diaphysis.  Not every species has this fusion.  I'm not sure yet which species this is.  Does that help?

[JohnJ]

I would look at the sloths.

[CDiggs]

49 minutes ago, Harry Pristis said:

I think you have the fused tibia-fibula symphysis along with the fibula diaphysis.  Not every species has this fusion.  I'm not sure yet which species this is.  Does that help?

First, thanks so much for reading and responding!

 

It definitely helps, at the very least it confirms I'm probably looking in the correct area of the skeleton and gives me another idea to consider, however I'm still having a hard time reconciling this visually.

 

So if this is the diaphysis of the fibula that would place the attachment point for the tibia in the area I've circled in blue on the following image which still doesn't look quite correct as I'd expect the diaphysis of fibula to be off to one side and the diaphysis of the tibia to be fairly central but the diaphysis in this case appears to line up with the intercondylar eminence where I've added in the straight line in red. I could still be totally off base with this critique however so I'll keep looking!

 

[CDiggs]

11 minutes ago, JohnJ said:

I would look at the sloths.

 

Thanks so much for the response!

 

do you agree then that this is a probable tibia or fibula?

 

I've been having a hard time finding reference images of sloth elements to compare to but it also hasn't been the top of my list for comparison.

[CDiggs]

I know this is a farily old thread but a bit of an update- This has been subsequently identified as as a left proximal castoroides tibia and is pathological after all.

[Scylla]

14 minutes ago, CDiggs said:

I know this is a farily old thread but a bit of an update- This has been subsequently identified as as a left proximal castoroides tibia and is pathological after all.

By whom? Just curious.

[CDiggs]

6 minutes ago, Scylla said:

By whom? Just curious.

Three paleontologists at the Houston Museum of Natural Science.