Pachyarmatherium leiseyi vs Dasypus bellus comparison

[Meganeura]

So I recently found an at-the-time unidentified small armadillo osteoderm in Paynes Creek. I immediately assumed due to its overall thickness - that being much thicker than the Dasypus bellus osteoderms I’ve found - as well as where I found it, that it was an osteoderm from the much rarer Pachyarmatherium leiseyi. My first step in confirming this was google, to which I found incredibly little information to discern between the two. There was plenty of info on D. bellus, however. 

My next step was to check here, including the  thread that @Shellseeker had created and linked me when I found a D. bellus osteoderm a few months ago:

Where I’d say that the results seemed inconclusive at best - all that was discussed was that P. leiseyi is “thicker”. No numbers, nor comparison.

 

Following that, I went to the next most reliable source - Richard Hulbert, who ID’d it as a baby glyptodont osteoderm. Which really didn’t seem quite right to me - it was MUCH too small as far as I was concerned, and also much too thick, being nearly as thick as my much bigger glyptodont osteoderm. So I spoke to @digit, who recommended I reach out to one Rachel Narducci also at FLMNH, specializing in Xenarthra, and thus would most likely be able to help me. She got back to me, after comparing with FLMNH’s own collection, that it was indeed a P. leiseyi osteoderm! I had also asked for more detail in comparing them, so I could properly make a post here comparing them, prompting this post!

 

So first Rachel’s description: “The difference in thickness is the big giveaway. I cannot find a single dasypus osteoderm that is anywhere near the thicknesses of the pachy osteos. The pachy osteoderms are also very rounded while those of D. bellus are polygonal with more angles and some even being rectangular. The dorsal outer surface of your pachy looks a bit worn (or the picture is kind of dark), but the peripheral figures around the central round figure are larger, more bulbous or inflated, and more separated than those of Dasypus bellus. D. bellus osteoderms have a larger central figure surround by the peripheral figures, but they are all pretty flat and very close together. The central figure of D. bellus also seems to take up more space on each osteoderm than it does in the pachys.”

 

Finally, here are the pictures - starting off with my own Pachy osteoderm:

 

 

Then the D. Bellus osteoderms I have:

 

A comparison of them:

 

And similarly from Rachel, the Pachy osteoderm is in the middle of 5 D. bellus osteoderms:

Comparing thickness:

 

And finally, more examples of P. leiseyi:

 

Hope this helps anyone else who is struggling to identify and compare between the two! 

[Nimravis]

Great write up Daniel and congrats on the find.

[rocket]

lovely material, thanks for showing

[JohnJ]

4 hours ago, Meganeura said:

She got back to me, after comparing with FLMNH’s own collection, that it was indeed a P. Leyseyi scute!

Great persistence and eye for detail, sir!

 

To accurately describe your find, what did she call them, again?  . 

[Meganeura]

3 minutes ago, JohnJ said:

Great persistence and eye for detail, sir!

 

To accurately describe your find, what did she call them, again?  . 

Osteoderm, my apologies! Well, actually she said "Osteo" after a point. I've definitely been using them interchangeably, but the correct term is Osteoderm!

I changed the wording in my post to correct that - better to be accurate!

Edited August 27, 2022 by Meganeura

[JohnJ]

1 minute ago, Meganeura said:

Osteoderm, my apologies! Well, actually she said "Osteo" after a point. I've definitely been using them interchangeably, but the correct term is Osteoderm!

True!  And she never called them by the popularly mistaken term, "scute".  

[JohnJ]

10 minutes ago, Meganeura said:

I changed the wording in my post to correct that - better to be accurate!

Edited 4 minutes ago by Meganeura

 

[Shellseeker]

Great thread, Daniel. It answers a fossil question and will help those who do not already know the answer,  to acquire knowledge quickly and efficiently. You also picked up a great fossil knowledge contact in Rachel.... Well done.

[Meganeura]

Gonna add this paper cause it has considerable information on P. leiseyi as well as the mean and range of thickness found for both D. bellus and P. leiseyi - notably that the former has a range of 3.5-5.5mm, 5.5 being the very upper end, with a mean around 4.2mm, and the latter a range of 5.5-13.3mm, with a mean of 9mm in one location, and 7.4mm in another. So if it's a quarter inch or thicker, it's a Pachy osteoderm.

https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-12.pdf