I found these rocks in the Oregon Coast Range many years ago and have always wondered whether the interesting image was a pseudofossil or an actual fossil. If it's a pseudofossil, any ideas on how it would form? If it's a fossil, what on earth is it? The image measures about 37 mm at its widest point.

Thanks for any insight you can provide! enter image description here

enter image description here

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    $\begingroup$ Upvote just because you included a scale. $\endgroup$ – John Apr 8 '17 at 23:10

It's been identified by a paleoichnologist as most probably a new species of Paleodictyon.


That certainly looks like a fossil, but of what is awfully hard to say.... Here's why:

You've only provided a planar surface and fossils (and their traces) exist in 3-D space. This is important because it helps pin down the entire structure of not only the fossil itself, but whether or not it was deformed over time. Your "fossil" shown here, may be a planar cross section through the fossil, but through which part if the fossil may be impossible to say.

Is it a radial plane through a soft-body sponge (like a deli slicer cuts through a salami)? Or is it an oblique slice through some swamp plant's seed pod that has been subsequently deformed into a circular shape? Here's where both that 3rd dimension comes into play as does the fabric of the host rock.

I would suggest looking for anything regarding fossils and geology of where you found this rock, narrowing down the particular unit that looks like this one, then seeing if there are any academic papers published that may include fossil descriptions similar to this. Good luck!

  • $\begingroup$ All good points, but I really can't tell you anything more about it, except that it's very two-dimensional, almost like a ghost image. I've asked several university earth science professors, including a paleontologist, but the specimen has proved a puzzlement to them all. There appears to be some tapering on the right side that might suggest the presence of a stem/pedicel in a different plane, but then I can't even tell whether it's a plant, a soft-bodied invertebrate, or something else entirely — maybe a just a weird pseudofossil? Thanks, Dave $\endgroup$ – Hominid Apr 11 '17 at 3:59

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