fossil ID

[Dangerjudy]

OK, it was not found in a cave, but a friend of mine found this, and wondered what it was:
http://notesfromtheattic.com/board/uplo ... fossil.jpg

It's in some rock (possibly shale) she got from a highway construction site to put in her garden.

[Scott McCrea]

Maybe this?


It's a neat one tho.

[gillip]

I don't think Scott is too far off. It looks like a trace fossil (ichnofossil). Essenitially, you have footprints of some critter moving arround when the sediment was unconsolidated. Probably as a result of the sediment being soft, some detail has been lost. Without knowing the age of the rock, it is hard to guess what made it. If the age is known, about the best you could hope for would be a SWAG.
You are probably looking at the bottom of the bed (layer). The raised portions are where there were depressions in underlying sediment.

[Illinois Caver]

I agree that it looks like a trace fossil as a gut feeling. Another option is a bryozoa (archimedes screw type) along with crinoid stem fragments. The specimen on the left side looks similar to that. I've seen similiar things in the limestone in Southern Indiana near Madison.

It would be nice to know what type of rock it is (limestone, dolomite, sandstone, etc...) though it looks like a limestone flavor.

Just my two cents...

-Troy

[Teresa]

What state, which area and what kind of rock? Have your friend put a drop of white vinegar on it and see if it fizzes.

Answer those three things, and I bet all the brains here can come up with a number of SWAGs.
I don't think it is a trace fossil. It looks either botanical or submarine to me. But I wouldn't hazard a guess beyond that until I found out whereabout it came from. If shale, it is likely botanical; if limestone, it's more likely animal.

[Dangerjudy]

OK what is a SWAG? I really don't know!

Here is her response:

"It came from an area near my home where I often find plant fossils in the shale. This is the only one I have ever seen like this. Also there is a place nearby where UAB students go to look at prehistoric salamander footprints preserved in what used to be mud. That's what it looks like to me: a dead lizard that fell in the mud.

Western Jefferson County, Alabama is the location. I will try to get out there with the vinegar this afternoon."


My guess is her reference to the footprint site is the Union Chapel trackways site. She lives out hwy 78 but not as far as Sumiton.

[CaverScott]

OK what is a SWAG? I really don't know!

scientific wild-assed guess

[Illinois Caver]

The location now adds a nice wrinkle to the mix. I have seen amphibian tracks from the New England area, but was unaware of any down South. I might have to check into this a bit more.

-Troy

[Dangerjudy]

http://gsa.confex.com/gsa/2006SE/finalp ... 102025.htm
http://www.agiweb.org/geotimes/oct03/NN_mine.html
http://gsa.confex.com/gsa/2006SE/finalp ... 101997.htm

[Larry E. Matthews]

That may be a poorly preserved Archimedes bryozoan.

If you look to the left of the fossil in question, you see another fossil that appears to be the central stem of an Archimedes bryozoan. Using that as a clue, it seems possible that the fossil in question is a more complete Archimedes bryozoan. The "rings" may be portions of the spiral fronds of the bryozoan.

Larry E. Matthews
Professional Geologist
NSS #6792-F

[Squirrel Girl]

I want more/better pix (not that the one posted isn't good), and more info. Is it on the undersurface of a bed of rock?

Here's what my friend who knows more about fossils than I do says:

Although it is tempting (and romantic) to make it into some sort of critter fossil, with ribs, a head and a tail (bent back as reptiles and birds apparently commonly are when they die), I think it is actually an assembly of ichnofossils. The smaller "tail" to the left has a chevron pattern that is highly unlikely for an actual tail structure, but makes a lot of sense for a feeding trace. The coarser "ribs" look like a heavier-caliber feeding trace. The "head" is either a sitz-mark or may be even a vertical burrow penetrating the bedding plane (you can see some smaller vertical burrows near the "tail"). If you look, you'll notice a couple more of the "rib" marks beyond the "head"; in front of its "nose", if you will.

[Larry E. Matthews]

People have a tendency to look at fossils, or FLR's (Funny-Looking Rocks) and see something that they are familiar with.

So, if it LOOKS like ribs, that is what they recognize, not the fronds of a bryozoan, since they have never seen a bryozoan.

But, I too would prefer to see the fossil up close and with my hand magnifier. Then we would have a better answer.

Larry E. Matthews
NSS #6792-F
Professional Geologist

[Teresa]

People have a tendency to look at fossils, or FLR's (Funny-Looking Rocks) and see something that they are familiar with.

That's the reason, (plus the scale) that if it is in Pennsylvanian shale, I would go for some sort of Equisitum related plant fossil, with the round bit being the growth bud.

So, if it LOOKS like ribs, that is what they recognize, not the fronds of a bryozoan, since they have never seen a bryozoan.

I've seen bryozoans, but am not a bryozoan expert. What matches my search engine of bryozoan it the little wormy bit down in the right hand corner. I could make myself believe the main attraction is an Archimedes screw if I could rationalize that round bit.

But, I too would prefer to see the fossil up close and with my hand magnifier.

Agreed. People sometimes don't realize that there is more to IDing rocks than just pictures.

[Dangerjudy]

She put vinegar on the rock. It didn't do anything but wet the rock.

[Larry E. Matthews]

OK. Here is a suggestion.

Mail me the fossil and let me look at it up close AND pass it around to about a dozen other geologists who work here in the same building with me.

The Tennessee Division of Geology is in this building and many other State Divisions in this building have geologists on their staff.

Surely, between all of us, we can figure out what it is.

I will mail it back to you within a week.

Here is my home address:

Larry E. Matthews
8514 Sawyer Brown Road
Nashville, TN 37221-2403