Ammonite or echinoid?

[TexasFossil]

Hi all! My son found this fossil in Pease Park, Austin ,TX, Travis County limestone. He wants to use it for our Christmas card! But we need to know what it is, so we can adjust the text on the card. It looks like an coilopoceras ammonite (see image below) , they are common in the region and the  number of lines seems right, but someone in a fossil forum thought it was an echinoid, like a star fish? What could it be? Does anyone have an idea? Thank you!!

 

Ammonites in the region:

 

 

[tmaier]

Mmmm. It's got a white dusty coating on it, and it obscures the details. If you buff it against your pants leg (use old pants), it will highlight the details more. Also, rub your fingers on the high points to create some contrast.

[sixgill pete]

I am not so sure it is either one. I would say definitely not an echinoid. If it is an ammonite, it is very, very, very worn. I really think it is just a rock worn by nature. But maybe someone will prove me wrong.

[TexasFossil]

Thanks! We'll try to buff it up in the morning. My son was hoping to find an ammonite, so we could use it for a Christmas card and say 'Twas the ammonite before Christmas', hahaha.

[DPS Ammonite]

Hopefully some our Fossil Forum members with Christmas spirit in the Austin area can show her son where he can collect some nice ammonites and other Texas fossils to put on his Christmas card.

 

TexasFossil, contact the Paleontological Society of Austin (join them too, they are kid friendly) and see if they can lead you to a site with great fossils.

[Fossildude19]

There is a slight possibility that this is the very worn inner whorls of an ammonite. 

 

Here is what I'm seeing: 

 

 

   

 

It is extremely worn, as stated. 

Not sure you could say one way or the other, conclusively. 

Regards, 
 

[Ludwigia]

I'd say that that's a very worn outer mold of the inner whorls of an ammonite.

[TqB]

10 minutes ago, Ludwigia said:

I'd say that that's a very worn outer mold of the inner whorls of an ammonite.

 

So would I.

[fifbrindacier]

8 hours ago, Fossildude19 said:

There is a slight possibility that this is the very worn inner whorls of an ammonite. 

 

Here is what I'm seeing: 

 

 

   

 

It is extremely worn, as stated. 

Not sure you could say one way or the other, conclusively. 

Regards, 
 

 

4 hours ago, Ludwigia said:

I'd say that that's a very worn outer mold of the inner whorls of an ammonite.

I agree it might be that.

9 hours ago, DPS Ammonite said:

Hopefully some our Fossil Forum members with Christmas spirit in the Austin area can show her son where he can collect some nice ammonites and other Texas fossils to put on his Christmas card.

 

TexasFossil, contact the Paleontological Society of Austin (join them too, they are kid friendly) and see if they can lead you to a site with great fossils.

You can follow this advice, i think it's really a good one and i know there are some places in Texas where there are a lot of ammonites. I swear you and your son good luck.

[BobWill]

It might help to see other views of the fossil. It has some radial symmetry but not five-way symmetry like an echinoderm of any kind. It could also be a coral but it may be just too worn to tell. If you have time you may be able to get some advice from a local collector about where to find a better example, or at least photograph one at a museum. I love the idea of using the re-written poem line

[TexasFossil]

oooh, thank you all!!! And thank you for the detailed investigation!! My son is only 6, and he is very proud of his find! Thank you again!!!! Everyone is so helpful on this forum!!

[erose]

I also agree that it is the impression made by the inner coil of a ribbed ammonite. Certainly not an echinoid. There are numerous types of ammonites that can be found at that site. Some more often than others. In fact about ten years back I led a summer camp group from the Austin Children's Museum there for about a half hour of collecting from the gravel bars. Most of the kids just found oysters and a few scallops. But one eight-year old boy found four completely different ammonites! All were fairly well preserved and none where the one common species. He brought me the first one and I was impressed. By the time he showed me the third and fourth I was flabbergasted...

 

Keep taking him back and he will eventually find even better specimens.

 

Also, at Pease Park the gravels are a mix from formations upstream but the banks are Grayson/Del Rio Formation.

[FossilGuy1024]

An alternative explanation could be that it’s a radial cross section of an ammonite chamber. Meaning if after the ammonite ended up in the creek and the whorls separated as they commonly do,  then broke across and rolled around some more you could end up with this. If you look at the top of the shell in the bottom middle drawing below I could see this as a possibility. What gets me is the symmetry of the outline of the piece which I think is not accidental. Also, the white patch toward the right side in the original posting could be infill of the siphuncle.

Illustration is from Ernst Haeckel’s “Kunstformen der Natur”, 1899

 

[TexasFossil]

Wow, thank you for that information!! I have attached our final Christmas card, my son was SUPER excited!! Hahaha. Thanks again!!

[ynot]

He looks real happy! nice!

Tony

[fifbrindacier]

Well, your son has a future in this domain, because i am far much older than he is and i found my very first ammonite this year, like him. So, i swear welcome to a future great paleontologist on this forum.