Costal vs. Scute vs. Osteoderm IDs

[Brandy Cole]

Location:  South Texas

Found:  Gravel, sand, low water

Estimated time:  Pleistocene 

 

I've been searching through info on scutes, osteoderms, reptile fossils, and types of turtle shell and plastron parts because we seem to have a lot of those in our area, but I'm having a hard time telling the difference.

These are my best guesses, and I'm hoping someone can educate me on the differences.

 

FRAG 1--I think this is a large turtle/tortoise scute fragment, but I'm not sure how to tell the difference between neural, costal, central, etc.

  

 

 

FRAG 2--I believe this is an osteoderm (because it looks like skin instead of part of a shell?), but I'm not sure the type.  Maybe alligator?

 

 

 

FRAG 3--My husband thought this may just be a rock, but I thought it looked like a fossilized shell plate of a turtle.  It's relatively thin.  We see a lot of these on the river.

 

 

 

FRAG 4--This looked like another osteoderm to me because it has a similar texture on top to Frag2.  But it's much thinner and the edges are more defined.

 

 

Any info would be a big help!  Thank you.

 

--Brandy

 

[Plantguy]

Hi Brandy, looks like you guys have a bunch of questions about some cool finds that I'll take a swag at. Im actually trying to sort thru my pile of boney armament that Ive picked up over the years myself and am focused right now on my turtle pile and am getting some help from UFlorida so I'll share some thoughts. Im definitely not a vertebrate person so I'll look for any vert folks or those with more knowledge to share additional comments/corrections. 

 

So looking at your 4 specimens I think they are too fragmental to narrow it down too much--unfortunately.  Frags 1,2 & 4 are definitely boney--what parts and from what I'm not sure. They've been tumbled so much that any diagnostic shapes or features have all been worn off. The porous areas in 1,2&4 suggest the internal boney cells/structure. Frag 1 might be turtle but Im just not sure. I can see that larger flat surface makes you wonder. Frag 3 does look suggestive as if it were a cast of something but I think its simply a neat shaped rock---maybe a fine grained sandstone?--one side being fresher and less weathered and polished than the other. 

 

Here's some turtle/tortoise pictures. First is to show the neurals or midline on the carapace shell--they generally have some symmetry and are attached to several of the vertebrae , the costals or the bones that the ribs are attached to (left and right sides)and usually have some identifying texture/shape and the peripherals around much of the edge of the carapace. You also have the base of the shell/or plastron to deal with in our finds and I wont go into all of its unique shapes/elements. The shape and features of the Nuchal bone above the head of the critter is often diagnostic....

Here's a closeup of the sutures between those bones of the carapace and the grooves that the non-boney organic scutes converying them leave when they fall off. Those are both important along with the shapes of the various bones and textures for identifying the type of tortoise/turtle. 

Here is a picture of some costals and some unique shapes for some Florida types that you probably have in Texas as well. Note the rib ends showing at the bottoms of the Chelydra (snapper) and Apalone (soft shell)...

Here's a picture of a neural of a large tortoise on the left (note the symmetry) as as well as a couple other fragments. Note the horizontal groove (sulcus) on the surface of the piece on the right and the internal pores visible in the lower right specimen. 

Here's a bunch of different osteoderms from Florida on the right of the photo along with 4 tortoise osteoderms on the lower left --one might even be something else which I've not confirmed yet(whitish colored). I believe you had many of the same Pleistocene aged critters over there. The last pictures are a closeup of the lower right 3 glyptodonts and illustrates how they slowly break down as they get tumbled and water worn and all the surface features/ornamentation gets worn off. 

Here's how similar they look in cross section. The two smaller/thinner ones are the glyptodont and holmesina osteoderms and the other thicker piece is a piece of large tortoise shell. 

 

So I will leave it here for now.....hope I gave you guys some things to think about. Keep hunting and as you all find more you'll probably run into some pieces that aren't so worn and have sharp edges/crisp features that will aid in readily identifying them down to a specific critter. I still have pieces that I have that are water worn and unidentifiable but I still remember the fun collecting them! Good luck! 

Regards, Chris 

 

[Brandy Cole]

Thank you so much.  This post is tremendously helpful, and the pictures are great.  It's really informative to see size, shape, and feature examples to compare my stuff to and to help me know what to look for when I go out.  The turtle diagram is also very clear and helpful.   

 

At this stage for me, it's hard to tell what has enough features to be ID'd and what doesn't. Posts like this help me learn.

 

I'm thinking of getting an organizer for what we've found.  I'm fond of all of our first finds even if I have to just make a card that says "undetermined".... Or several cards.  :-)

 

Thanks again,

Brandy

[Plantguy]

11 hours ago, Brandy Cole said:

Thank you so much.  This post is tremendously helpful, and the pictures are great.  It's really informative to see size, shape, and feature examples to compare my stuff to and to help me know what to look for when I go out.  The turtle diagram is also very clear and helpful.   

 

At this stage for me, it's hard to tell what has enough features to be ID'd and what doesn't. Posts like this help me learn.

 

I'm thinking of getting an organizer for what we've found.  I'm fond of all of our first finds even if I have to just make a card that says "undetermined".... Or several cards.  :-)

 

Thanks again,

Brandy

@Brandy Cole Glad to help! If you are able to safely visit a fossil club during these covid days you can always show your finds to some of the local hunters and they'll give you their opinions as well and you can tap into their local knowledge.. They may also have some Texas fossil books/articles to suggest. 

If you want lots more on osteoderms I saw this online today....its got more pics of other types/shapes and their locations on the various critters and lots of other details! 

NUMBER40

PEARCE-SELLARDS SERIES

The Armor of FOSSIL GIANT ARMADILLOS (Pampatheriidae, Xenarthra, Mammalia)

A. GORDON EDMUND

JUNE 1985 TEXAS MEMORIAL MUSEUM, UNIVERSITY OF TEXAS AT AUSTIN

Here's a direct link to see the document online: 

https://repositories.lib.utexas.edu/bitstream/handle/2152/29906/tmm-pss-40.pdf?sequence=1

 

Regards, Chris 

[Brandy Cole]

17 hours ago, Plantguy said:

@Brandy Cole Glad to help! If you are able to safely visit a fossil club during these covid days you can always show your finds to some of the local hunters and they'll give you their opinions as well and you can tap into their local knowledge.. They may also have some Texas fossil books/articles to suggest. 

If you want lots more on osteoderms I saw this online today....its got more pics of other types/shapes and their locations on the various critters and lots of other details! 

NUMBER40

PEARCE-SELLARDS SERIES

The Armor of FOSSIL GIANT ARMADILLOS (Pampatheriidae, Xenarthra, Mammalia)

A. GORDON EDMUND

JUNE 1985 TEXAS MEMORIAL MUSEUM, UNIVERSITY OF TEXAS AT AUSTIN

Here's a direct link to see the document online: 

https://repositories.lib.utexas.edu/bitstream/handle/2152/29906/tmm-pss-40.pdf?sequence=1

 

Regards, Chris 

That's a good idea.  That book is also super helpful! Thanks for all the tips!