Turtle Nuchal Bone

[GPayton]

Despite how common they seem to be in places like Florida's Pleistocene deposits, I've never been able to find a complete turtle nuchal bone here in Texas's similarly aged formations until just this last week. Unlike almost all of my other Pleistocene finds which have come from the stretch of the Brazos River closest to Houston, this one is from the adjacent and much smaller Colorado River. Since the Brazos has been high all summer due to the extreme amounts of rain we've gotten this year I decided to try out some nearby locales and they did not disappoint. I've got a couple more posts to make in the ID section of the forum after this one since there's a good amount of stuff I can't seem to attach any solid names to, so bear with me. 

I've been referencing some of the excellent photos provided by @Harry Pristis the last time I made a post like this in this thread here: 

 

http://www.thefossilforum.com/index.php?/topic/106885-turtle-nuchal-bone/

 

Fortunately, this time the bone in question is more than just 50% complete, so a species or genus ID should be easier to achieve. Hopefully some of the forum's resident experts on Pleistocene material from the southern US can be of some help in identifying which particular turtle this is: @Shellseeker @garyc @darrow

 

 

Edited August 23, 2021 by GPayton

[garyc]

I have found a few nuchals and I think that’s what you have, but I’m far from a turtle expert…

[Natalie81]

+1 for turtle

[Harry Pristis]

I've checked my sources, and I don't have an ID for you.  I'm sure there's some overlap with Florida's turtle fauna, but you might want to compare with a Texas collection.  Unless there is gross erosion of the specimen, I might check some of the smaller turtles like Kinosternon which have relatively smooth carapaces.

[GPayton]

On 8/23/2021 at 1:35 PM, Harry Pristis said:

I've checked my sources, and I don't have an ID for you.  I'm sure there's some overlap with Florida's turtle fauna, but you might want to compare with a Texas collection.  Unless there is gross erosion of the specimen, I might check some of the smaller turtles like Kinosternon which have relatively smooth carapaces.

I suspect river erosion is the likely culprit, as I can see the faint markings of horizontal ridges on most of the surface. Oh well, can't win them all I suppose. 

[Plantguy]

 

@GPayton

Neat find. Can we get a ventral view of this guy? Might be able to get you an answer although it does look pretty abraded.

 

I've got a bunch of nuchal stuff and might be able to tap some other resources. 

I want to particularly take a closer look at Pseudemys, Trachemys, Glyptemys and Deirochelys. 

 

Here's a good diagram/article for some Maryland examples that may help narrow this down and may or may not apply to Texas.

From: 

Amphibians and Nonmarine Turtles from the Miocene Calvert Formation of Delaware, Maryland, and Virginia (USA)

Jul 2013 Robert E. Weems Reed A. George

 

 

https://www.researchgate.net/figure/1-3-top-holotype-nuchal-of-Chrysemys-isoni-new-species-CMM-V-4664-in-anterior_fig6_274905845

These are Miocene though but we may be able to figure out a younger Pleistocene example using the genera and their forms....not sure what made it to the Pleistocene...

 

 

 

Regards, Chris 

Edited August 25, 2021 by Plantguy
added image/files/links

[GPayton]

Like you said @Plantguy it's definitely abraded which must make an ID difficult, but here's the ventral view you wanted. One from straight above looking down, the other at an angle so the faint indentations are visible. 

[Plantguy]

Thanks for the additional photos!

@GPayton

I was hoping something might come close to one of the bunches I have but those parallel linear groovesin yours have thrown me. I have a couple smaller nuchals/unidentified specimens that have some slight resemblance but with a keel and I have little confidence that they are the same.  Here's one still unidentified example I have.

I did solicit help. Unfortunately they werent able to offer any conclusive ID from the photos alone because of the wear/preservation--maybe looking at in person could help but were not sure. Its very hard to determine the real morphology vs waterwear in your specimen..  Possibly an emydine emydid but tentative/just not sure. The question was asked if there are any other finds or other shell fragments/plastral bits from that locality? 

 

Just for fun I looked up a chart showing the fossil subfamilies in Emydidae from Wikipedia --- I just wanted to show the many possibilities within Emydinae and Deirochelyinae alone...

Note: I'm not familiar with Wilburemys from around here...

 

 

Regards, Chris