found near Austin, Texas. Need help with an ID?

[Jared C]

 

 

Found in Round rock Texas, just north of Austin. Pieces found among weathered rubble at base of a limestone cliff rich in devils toenails, next to a creek. The Texas pocket geologic map I'm referencing is a bit confusing, showing the area to be at somewhat of a confluence of the "Del rio clay and Georgetown formation", Edwards limestone, Eagle ford group, and Buda Limestone.

 

 

I'm very cautious about being the annoying newbie who calls every little rock he finds a fossil, so when I came across four large, curved, tooth shaped stones amid many devils toenails and scallops today, I was hesitant to get my hopes up. My thoughts are that they may be too large to be the teeth of any western interior seaway life that I know of - based on a google search, if these are teeth, they'd be as big if not bigger than even the teeth of tylosaurus, so I have my doubts. That said, my other amateur hunch is perhaps these are fillings of limestone holes that hardened. But I'll let you guys be the judge of that.

Below is the first, stuck in matrix on almost every side - there is a small, smooth exposed patch in the right middle. Measurements are quite roughly 3.5 inches from the tip to the base of the matrix, I have no ruler handy at the moment

 

Below is another look, closer this time an centered on the tip

 

Here is the same piece, curved in towards me this time

-

 

And one last side profile to show the suspiciously smooth and even curvature

 

Now, I'll show the other pieces I found. All of these , the one above included, were found within a few square meters of each other. It's possible they're associated.

 

below is another angle of the piece above:

 

 

And to finish, these last two pictures are of two completely separate bits, each only getting it's one picture

 

 

...and

 

 

 

I would greatly appreciate any possible ID's or explanations! Thanks for reading through!

[Rockwood]

29 minutes ago, Jared C said:

That said, my other amateur hunch is perhaps these are fillings of limestone holes that hardened. But I'll let you guys be the judge of that.

Being from Maine, I know little firsthand about rudists. That said, I suspect the hole that was filled was the living cavity of one of these bivalves.

[Scylla]

I agree with Rockwood, internal mold of rudist. 

[Jared C]

1 hour ago, Scylla said:

I agree with Rockwood, internal mold of rudist. 

Thanks! I must admit that the resemblance is uncanny!

[Rockwood]

1 hour ago, Jared C said:

Thanks! I must admit that the resemblance is uncanny!

I did make it to Kansas once, in a rental with Texas plates. 

[JohnJ]

11 hours ago, Jared C said:

 

 

Found in Round rock Texas, just north of Austin. Pieces found among weathered rubble at base of a limestone cliff rich in devils toenails, next to a creek. The Texas pocket geologic map I'm referencing is a bit confusing, showing the area to be at somewhat of a confluence of the "Del rio clay and Georgetown formation", Edwards limestone, Eagle ford group, and Buda Limestone.

....

 

 

below is another angle of the piece above:

 

 

As a local in your area, I tend to agree with the internal rudist cast.  Although they can vary, the parallel ridges are typical in some specimens.  They are frequently mistaken for teeth.