Help a 5th grader

[Ms. Woo]

One of my students found this near Jacobia Texas and would like it identified if possible. I have more pictures of it on the forum's Facebook page.

[Herb]

looks like a cut septarian nodule to me

[DPS Ammonite]

I took a look at the Facebook photos. Better close-up photos of the cut side might show that this is more than a concretion. I am especially interested in the thick white rind. Is sort of has the overall shape of a rudistid bivalve. Details of texture will help. 

[GeschWhat]

Now that is something you don't see everyday! 

[Ludwigia]

I was also thinking of rudist.

[Rockwood]

It does look like the rudist/ septarian combo is on the menu here. 

[Fossildude19]

+1 for rudist. 

Images.

[BobWill]

Outside of overall shape, (and only then if you squint and stand on your head) what characters of a rudist does anyone see here? There may be something I'm missing but if shape were enough we need to revisit some of those "dinosaur eggs". I don't see the usual growth lines or layers. If this were ever something alive I don't see enough evidence to point to what it might have been to support giving it a name.

It also came from an area dominated by two formations. They are described in the Geologic atlas of Texas with the phrase "marine megafossils scarce." The Neylandville Marl and the Marlbrook Marl are just not places people go looking for fossils but i would like to hear from anyone who has found any there for some context.

[Fossildude19]

10 minutes ago, BobWill said:

Outside of overall shape, (and only then if you squint and stand on your head) what characters of a rudist does anyone see here? There may be something I'm missing but if shape were enough we need to revisit some of those "dinosaur eggs". I don't see the usual growth lines or layers. If this were ever something alive I don't see enough evidence to point to what it might have been to support giving it a name.

It also came from an area dominated by two formations. They are described in the Geologic atlas of Texas with the phrase "marine megafossils scarce." The Neylandville Marl and the Marlbrook Marl are just not places people go looking for fossils but i would like to hear from anyone who has found any there for some context.

 

All very good points, Bob. 

More images are needed for sure. 

I will always defer to a local who knows the area. 

Maybe we were a bit hasty with the rudist proclamation. (At least, I was. ) 

[Ms. Woo]

[Fossildude19]

Definitely looks very much like a concretion/septarian nodule. from this angle.

 

The concentric layers area good indication of this.

Some pictures of the sides and bottom would help as well.

[DPS Ammonite]

I thought that there might be a possibility that a cellular texture (sort of like petrified wood) would show on a close-up photo. I see none. Durania sp. rudists with a cone shape occur nearby. This is not one, only a neat concretion that most likely will fluoresce in both short and long wave fluorescent lights.

 

Thanks for showing it to us.

[BobWill]

If some of your students are interested in fossils Jacobia is very close to a world famous collecting site that's open to the public. A field trip to Ladonia is always a hit with kids and you could probably find a guide to help out through the Dallas Paleontological Society.

[abyssunder]

It might be a rudist with a septarian core in the body cavity, with its celluloprismatic mesostructure and the pallial canals running to the extremity of the outer wall, but without a transverse polished cut is just a guess.

 

 

[Ms. Woo]

At least one group of our kiddos usually go to NSR in Ladonia on a field trip yearly. I think we have a group going next week =) We put a black light on it today and go some really nice colors out of it.

[Rockwood]

On 4/24/2018 at 9:52 PM, Ms. Woo said:

At least one group of our kiddos usually go to NSR in Ladonia on a field trip yearly. I think we have a group going next week =) We put a black light on it today and go some really nice colors out of it.

This post is a good example of a concept in paleontology.

It's quite necessary to maintain a rich palate of possibilities around each proven. The experts tend to keep these private, but it is sort of the matrix that holds the process together.