Unknown Fossil Gilroy California

[Mattman]

Hi I often hike in the hills near my house in Gilroy California in the Santa Cruz Mountains. I found this in a very light piece of stone common in my area. The entire fossil shown is slightly smaller than a dime. Any ideas what it might be? Thanks!

[Plantguy]

Aint that neat! Not sure on that one...my first impression was that it looked crabby to me...maybe part of the carapace of one of those little mole crabs we used to pick up as kids at the beach or what some people call sand fleas...part of a fish scale?...hmm..wait for others input..

 

Regards, Chris 

[Fossildude19]

Very interesting item. 

I can't decide if it looks like a fish scale, or some sort of arthropod. 

It appears that there is more of it under the rock. 

More prep. might reveal more detail. 

Regards,

[FossilDAWG]

Perhaps part of the carapace of a galatheoidid crab.  See here for some examples.

 

Don

[Fossildude19]

Don and Chris, 

 

Thanks for teaching me something new today! Amazing , the amount of collective knowledge on this forum.  

Thanks again, gentlemen!

Regards,

[PFOOLEY]

10 minutes ago, FossilDAWG said:

...See here for some examples.

 

Thanks for the link...what an awesome website! 

[FossilDAWG]

Just now, PFOOLEY said:

 

Thanks for the link...what an awesome website! 

That website has been built by Forum member MBfossilcrab.  It is his own personal collection, and it is indeed incredibly awesome. 

 

Don

[fifbrindacier]

I think you got it @FossilDAWG, thanks for that instructive link and thanks to @MBfossilcrab to share it on the net.

[Mattman]

Don, I think that is a very good match. Thanks!

 

 There is a lot of this rock in the hills near my house. I will try to inspect them closer and try and split some open to see if I find more fossils. I find quite a few fossilized sea shell clusters in areas around Santa Clara County and beyond. Some of them are quite large and numerous. I generally leave them for others to enjoy but I brought a small one home a few years ago. The three loose shells I carefully removed from some loose rock from the eroding cliff near Davenport CA. these shells were about 20' underground until nature uncovered them for me to find. I am wondering if the large shell on the left is of a species that survives today?

[tmaier]

The one on the left looks like a freshwater mussel, but something odd has happened to it (or it is the strangest mussel species I've ever seen). It is a fairly modern one, because it still has the outer layer of organic "skin" covering it (called periostracum). Errosion? Mmmmm...

The two at the bottom look like coquina shells, a tiny saltwater clam. Not sure about that, can you flip them over and get a shot of the inside?

Also, when you present a new specimen, you should start a new thread, so each subject gets its own thread.

How big are these shells?

[Coco]

Hi,

 

I think left shell is recent Pholade family (shells which dig rocks) :  https://www.google.fr/search?q=pholade&client=firefox-b&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjmxd-u0brQAhVDthQKHcAIAc0Q_AUICCgB&biw=1440&bih=736

 

Coco

[Mattman]

The big shell on the left is 1.4" x 3". The small shells are .6" x 1.25". The thing about the larger shell that intrigues me is the intricate detailed structure at mid-bottom. There was a very thin "bubble" of shell that was at the lower R of the piece that did not survive the trip back to my house. It was quite the specimen when it was whole. The shell was actually encased in hardened mud like the shell cluster at the R of the photo but was a much more crumbly substrate.

[fifbrindacier]

I think @Cocois right. Maybe that shell on the left has so an odd shape because of the support on which it grew

[Mattman]

 

I found a close match for the large shell Penitella penita. Some photos look very close except for the small end is pointy on mine and flattened on the specimens pictured. An interesting fact is that they do bore themselves into soft rock. My shell was found roughly 100' from the ocean. I do wonder how old it is.

 

http://www.bily.com/pnwsc/web-content/Family Pages/Bivalves - Pholadidae.html

[fifbrindacier]

14 minutes ago, Mattman said:

 

I found a close match for the large shell Penitella penita. Some photos look very close except for the small end is pointy on mine and flattened on the specimens pictured. An interesting fact is that they do bore themselves into soft rock. My shell was found roughly 100' from the ocean. I do wonder how old it is.

 

http://www.bily.com/pnwsc/web-content/Family Pages/Bivalves - Pholadidae.html

I think it matches well.

[doushantuo]

https://decapoda.nhm.org/pdfs/33333/33333.pdf

[doushantuo]

a short guide to endoliths/cavicoles:

 

bull45-2-130-134.pdf

[tmaier]

Doh! Yes, that is a piddock shell. The brown stuff on it fooled me.

[Mattman]

Lots of info. it seems that this shell is in very good condition and maybe not so old.