What and how?

[3RZUL13]

Before I get stoned to death for posting this here (lame pun intended)…let me just say that I honestly have no clue what I’m looking at here but I am not suggesting, nor am I of the mind—that it’s a fossil, but it was just so strange lookin’ that I couldn’t help my curiosity, so here I am asking for opinions on what caused this to form and what it’s composed of most likely (if anything other than limestone, that is….    (-__-).

 

location- far nw San Antonio, tx , just outside the foothills of the hillcountry (helotes, tx)

 

Again, I do want to apologize if this belongs in a strictly geological forum somewhere, I’d have probably posted it there instead, had I been aware of one existing which was similar to this platform but exclusively for weird ugly rock identification help (lol). Thanks in advance. 

 

[3RZUL13]

Risking additional embarrassment and the privilege of learning more facts about limestone and all the fun shapes it comes in…. I’m dying to know….Could somebody please tell me more or less, what the odds could be….of finding this particular shaped piece, plus all the other peculiar pieces previously noted…in my little backyard limestone {*turtle*} pit?…..bottom two here are this *rock*, and the top two obviously were snipped off a Google search.   
 
Thoughts?

 

 

 

 

 

 

 

 

 

[debivort]

I'm afraid it looks like geologically weathered limestone to me.

[doushantuo]

Agree with D.no vertebrate cranium

[Randyw]

If you really look closely at your turtle skull pictures you will begin to see the differences. Notice the suture lines in the turtle skull? All skulls have them. No suture lines then no skull…. Also both sides are simetrical. (Both the same) wich your rock isnt. As to the odds of finding something that looks like this. Really good. Everyone here has found “look a like” stones. Mother nature is a wonderful artist. Pair that with the human trait to paredilia (sp) and you have very high likely hood of finding things that look like other things.

Edited May 10, 2023 by Randyw

[JohnJ]

3 hours ago, 3RZUL13 said:

Risking additional embarrassment and the privilege of learning more facts about limestone and all the fun shapes it comes in…. I’m dying to know….Could somebody please tell me more or less, what the odds could be….of finding this particular shaped piece, plus all the other peculiar pieces previously noted…in my little backyard limestone {*turtle*} pit?…..bottom two here are this *rock*, and the top two obviously were snipped off a Google search.   
 
Thoughts?

 

Is embarrassment really a 'thing' when learning new concepts?   

 

As water percolates through the aquifer, it dissolves limestone through a complex network of cracks, holes, channels, and caves.  Over time, chunks of this "network" are broken apart by a number of causes and further weathered.  The result can be natural artistry that reminds us of things we are familiar with.

 

(If borrowing images from the web, please crop them to remove any seller or price information.  I have edited the images in your post.  Thanks.   )

[ClearLake]

@JohnJ beat me to it (and probably said it better anyway), Rain water is often slightly acidic and when it meets with limestone, it dissolves it over time into all sorts of wonderful shapes.  You have found one!

[Mahnmut]

Hello and welcome.

Organic looking shapes in limestone are often related to chemical weathering, as stated above. Landscapes where this occurs at greater scale are called karst, so maybe this entry is of interest to you:

https://en.wikipedia.org/wiki/Karst.

Of course limestone can contain fossils at the same time its being eroded into fossil-like shapes, the first "bones" of Karst rock I found as a youngster reveiled themselves as being no bones at all by containing little gastropod shells.

While I am sure it is no skull you found, I cannot tell from the pictures if the dark things in the cavity of your rock may be something fossil,  sharp macrofotos may help there.

Best Regards,

J