Arcadia Park Creteceous Fossil

[Jumpinghorse]

Hi everyone I hope I was able to get the photo on here properly for you. (I attached it) I have no idea what this is and have found nothing like it on the internet. Plus, I am green as grass with ID and hunting! Here is brief history on the find. I found this in Dallas Texas in what used to be an old quarry (General Portland Cement) in Arcadia Park. I think it is cretaceous and from the Eagle Ford Zone. It is about 7-8 inches long and the backside is a smooth, half, tube-like shape. Any ideas would be great. Thanks

[Fossildude19]

Hello Jumpinghorse!

Picture is ok - a little blurry.

I don't know much about that area, but, ... is it possible that it is part of an ammonite?

I Googled : Eagle ford formation fossils texas

and this was the first hit that came up - http://www.northtexa...esEagleFord.pdf

(plate 14, fig. 3), Acanthoceras sp.??? This pic looks slightly similar, but nowhere near as curved?

May be helpful. Maybe not.

Thanks for sharing, ... and putting up with guesswork!

Edited May 19, 2010 by Fossildude19

[Bill]

Hi Jumpinghorse, welcome to the forum,

pictures of the other surfaces would help with an id, if possible.

[Xiphactinus]

Hi Jumpinghorse. What you have there is a fragment of the hinge of a giant Inoceramus clam. The crystaline structure of the shell material is very diagnostic. Some of these shells were 4 feet wide!

[LanceH]

Yep, oyster shell but the size is quite surprising to me cause I've only seen itty bitty versions around here not 7-8 inches.

[Jumpinghorse]

Thank you all so much. I took this picture when I had it out of storage but I will take more photos as soon as I can. When I get it back out I will measure the fossil because you know how us women are with that sort of stuff. LOL! Thank you all again. I cannot wait to do more research on the Giant Inoceramus clam as well.

[Tony Eaton]

I guess it is not hard to guess what member of the Eagle Ford shale, (Arcadia Park = type locality of Arcadia Park member).

Maybe it is a Rudist "clam", Durania? That's my guess because the the straight shape. If I was more organized I'd be able to find an example or two that are more whole where it is most obvious what they are.

[Jumpinghorse]

Hi there! I found this as well, Not sure if it's anything. Maybe a plant imprint?

[Jumpinghorse]

Here is some lignified wood with crystal growth.

[Jumpinghorse]

I found this here in the Florida Keys. The gastropod is broken but it shows the beautiful crystalline growth inside

[Plantguy]

Hi there! I found this as well, Not sure if it's anything. Maybe a plant imprint?

Hi Jumpinghorse, nice finds you have there.

I dont believe you have a plant fossil imprint here. Rather, it looks more like a "dendrite" to me, which are simply manganese oxide crystals which have formed from ground water. Sometimes they are called "pseudofossils" because they look like fossils. Most of the time they are very dark in color and develop over time into the shape of the branches in a tree. A few of the areas on your sample show that characteristic tree like pattern.

Heres a sample of well developed dendrites from Germany to compare yours with.

Welcome to the forum!

Regards, Chris

[Tony Eaton]

Regarding the potential pseudofossil, years ago I found a bed of what could be the very same thing? I think this is just above the famed "Atco" (shark tooth) member of the Austin Chalk. This was from a wall in a parking lot along Marsh Road in Carrollton, Denton County, TX. This is from very fine grained white chalk.

The "fossils" do not match the dendrites I commonly find in septarian concretions just a bit "deeper" in the older Eagle Ford formation. They are clearly bisymmetric and have a consistent size and uniform shape. There is also clearly a "spine" of some sort running through the middle. Although these details no longer are preserved for me to photograph now, the ends had hair like or tentacle like structure. My first impression was a fossil squid, but more realistically I'm thinking some sort of trace fossil or simpler invertebrate or plant. Could be some sort of pseudofossil too.

Edited May 24, 2010 by Tony Eaton

[erose]

Scrappy plant fragments have been reported from the Eagle Ford Group in several papers (the scientific kind). A couple of years ago I saw someone find a "Calamite-like" fossil maybe an inch in diameter or more. It also was in a fine-grained-white limestone. The rusty orange impressions could be plant remains. But I agree the black looks like dendrites.

[JohnJ]

I think the "wood" you've shown is calcite. It can look a lot like wood, but it is commonly found as 'seams' where it formed in the faults and fractures of the Austin (chalk) Group formations. In those same formations, there are a lot pseudo-fossil type forms created by various minerals leaching through micro cracks in the chalk. Your "plant imprint" appears to be the result of this type of mineral deposition. Notice on the edge how that layer carries through your rock. Another clue that you were likely hunting in Austin Group rubble is the fragment of large Inoceramus clam. They are very common in those formations.

Good luck in your new hunting grounds.