Hesperotestudo epiplastron?

[darrow]

Collected this about a week ago on a gravel bar in a local river near Houston that is mostly late Pleistocene material.   I've labeled it Hespertestudo crassiscutata based on the size. 

 

Can someone confirm this is the left epiplastron?  

 

Thanks,

Darrow

[digit]

That would have been my guess if it had been pulled from the Peace River (though it would be jet black then).

 

@Harry Pristis may have more experience with specimens from this species.

 

 

Cheers.

 

-Ken

[Harry Pristis]

Here's the help I can give:

 

 

[ClearLake]

That looks like one big turtle shell fragment!  We had this issue a week or so ago with another turtle shell fragment, hopefully someone has a comparative specimen or at least a picture from a publication that the one in question can be compared to, as not all turtle shells look alike. Maybe @turtlesteve can help with this.  @darrow, you had a very specific suggestion, did you have something from the literature that led you to this specific ID?  I see there are at least a dozen species of this genus with at least one previously reported from Texas. 

[turtlesteve]

Well, I think I agree with you on left epiplastron, and that it was a very large tortoise.  
 

Hesperotestudo seems like a reasonable ID given the size and age, but I do not know enough to confirm a species ID.  The examples of Hesperotestudo I can find pictures of all have the undivided gular as seen here.  Note that this bone often shows variable shape and/or sexual dimorphism in modern tortoises.

 

Nice find!  Now go find the rest of the shell

[darrow]

2 hours ago, ClearLake said:

That looks like one big turtle shell fragment!  We had this issue a week or so ago with another turtle shell fragment, hopefully someone has a comparative specimen or at least a picture from a publication that the one in question can be compared to, as not all turtle shells look alike. Maybe @turtlesteve can help with this.  @darrow, you had a very specific suggestion, did you have something from the literature that led you to this specific ID?  I see there are at least a dozen species of this genus with at least one previously reported from Texas. 

Probably too specific...  ID based on nothing more than size, age, which really isn't enough to get to a species.  

 

Found this online but haven't had a chance to look at it closely...

 The Fossil Turtles of North America, Hay, O.P. 1908. https://archive.org/details/fossilturtlesofn00hayo/page/n9/mode/2up 

[Harry Pristis]

4 hours ago, turtlesteve said:

Well, I think I agree with you on left epiplastron, and that it was a very large tortoise.  
 

Hesperotestudo seems like a reasonable ID given the size and age, but I do not know enough to confirm a species ID.  The examples of Hesperotestudo I can find pictures of all have the undivided gular as seen here.  Note that this bone often shows variable shape and/or sexual dimorphism in modern tortoises.

 

Nice find!  Now go find the rest of the shell

 

Steve . . . The gular is a keratinous scute, not a bone.  Are you saying that you see a margin of a scute you identify as a gular?  Scutes don't preserve well as fossils.  Please don't confuse the two in your writing.

 

 

[turtlesteve]

Harry, I see your point here.
 

The term “gular” is ambiguous - it can mean the scute specifically, or the projection or horn at the front of the plastron (which comprises the front part of the gular scute and the corresponding part of the epiplastron).  The latter was my intent but my writing was sloppy.  It is more proper to say “gular scute” for the former and “gular projection” / “gular horn” for the latter.

 

I can see the line on photo #3 that differentiates the gular scute - It must be present on the bottom surface on photo #2 but I cannot make it out precisely.