Large Limpet Keyhole Fossil? 18cm (7”) Mystery desert find

[Nat111909]

Hi. This fossil was found in the high desert east of Bend, Oregon, but is not likely from this area. Most of the fossils in this area are wood…I’ve never heard of anyone finding a shell.
 

I found it placed next to a trail that is used daily by many people. I have no idea who left it or where it is from. 

The only photos I have found online that looked close were for a couple of New Zealand keyhole limpet fossils which were documented in the 1970’s. 

The fossil has a hole in it that looks similar to a keyhole, but is partially filled in and not visible from the inside of the shell.

 

Any help is appreciated. Thank you!

 

 

 

[FossilDAWG]

First, welcome to the Forum.

 

Your shell is a limpet, though not a keyhole limpet as there is no opening at the apex.  I'm not convinced it is a fossil, especially as you say shell fossils are not known from the area.  It's more likely (in my opinion) to be a modern shell, possibly the owl limpet Lottia gigantea which occurs along the Pacific coast and gets to be very large.  There are various possible scenarios that would result in such a shell being transported by human activity from the coast to your area.  The structure attached to the shell in photo #4 is the base of a barnacle.  Other structures you show attached to the shell are the remains of the calcareous tubes of polychaete worms such as Spirobus.

 

Don

[abyssunder]

I agree with the above. The trace fossils are determining the geological age. I think I can see the combined bioerosion on all surfaces of the shell ( Rogerella, Maeandropolydora, Entobia) also the barnacle attachment scar and the Spirorbis colony.

Edited April 16, 2022 by abyssunder