Tapir or Just Really Small Horse Tibia?

[GPayton]

I found this broken end of a long bone several months ago near Houston in the late Pleistocene gravel deposits of the Beaumont and Lissie Formations. Here are some pictures (with each grid on the graphing paper being 1/4 of an inch): 

 

 

I know that it's the end of a tibia because the grooves on the end are shaped to match an astragalus (ankle bone), and that their slanted angle indicates a perissodactyl like a horse, tapir, or rhino rather than an artiodactyl like a bison, pig, deer, or camel. Based on the size of the bone, I think I can pretty easily rule out rhino, which leaves only horse or tapir as a possibility. 

Now, I've never found a single tapir bone in all the time I've spent hunting in this area, whereas it seems like there's such an overabundance of horse material that I'm literally tripping over their teeth and bones any time I take a step (that and turtle shell fragments)! Needless to say the odds are definitely in favor of horse.

What's stumped me is that it seems just too small to be a horse bone - at the very least, not one from an adult anyway. I know that three-toed horses were often smaller than their one-toed cousins, and I've found their teeth before as it's not too uncommon for them to wash down from the older formations north of where I'm hunting, so that's also a possibility. My main problem is that I can't find any reliable measurements online for the distal end of a tapir tibia to compare mine to. So if anyone has any old literature with some helpful information or (even better) pictures, I'd love to see them. 

Any help is appreciated! 

@Shellseeker @Harry Pristis @garyc

Edited August 17, 2022 by GPayton

[Brandy Cole]

I had this one marked down as distal tapir in my collection, but I can't remember how I came to that ID as opposed to horse.  I think I may have compared it to several equus astragali and noted the differences.  So, use for comparison with a grain of salt.  It appears different from yours to me.

 

 

[GPayton]

@Brandy Cole - can you take a measurement across the end of the bone that you can see in your second picture? I want to compare it to mine and see how much smaller the one you have is or if they're close to the same. 

I also tried fitting some horse astragali against the grooves like you did and although one came close to fitting it wasn't an exact match. I tried a smaller three-toed horse astragalus I have as well and it was definitely too small. 

[Brandy Cole]

It's about 5cm across and 4cm tall.

[GPayton]

On 8/17/2022 at 7:32 PM, Brandy Cole said:

It's about 5cm across and 4cm tall.

That's pretty much an exact match for mine. Maybe they look slightly different due to wear from tumbling in the river? 

[Brandy Cole]

@GPayton. Could very well be!