Wednesday, June 1, 2011

Mystery traces

For my first post on this blog, I'm going to share some photos of some mysterious traces a friend of mine discovered in August 2010 when we were doing field work in west-central Alberta. I've shown the photos to a few people in the geoscience department at the University of Calgary, but no one knows what it is. My first guess of some sort of cross between a deer and a trilobite seems unlikely.

Maybe there is someone out there who can solve the mystery...

Here's what is known about them:
-Found covering one side of a large boulder in a pile of rocks at the base of some cliffs
-The cliffs are cherty limestone, from the Lower Jurassic Nordegg Member of the Fernie Formation
-The rock is probably also Nordegg, but if it came from high enough up, it could be from the Rock Creek Member. It was wet and muddy and we didn't spend a lot of time figuring out what it was.


  1. Not being a paleontologist I have no idea what they are either, though the deer-trilobite hybrid makes a lot of sense to me (at least on a non-temporal level).

    Welcome to the geoblogosphere! I'm subscribed!

  2. Thanks Ron! I was on a field trip the other day and someone found a cast of a trace that was quite similar to these in Upper Jurassic rocks. But no one could identify it then either.

  3. I think, if these traces were in Cambrian or Devonian rocks, they'd be called Rusophycus without hesitation (and perhaps Cruziana, where they're stretched out into trails, e.g. above the scale card in the 3rd photo). The only objection to this, of course, is that Rusophycus and Cruziana have been attributed to trilobites, which makes their appearance in Jurassic rocks a problem. However, if you subscribe to Seilacher's contention that "Ichnofossilien werden nicht in Stellvertretung ihres Urhebers benannt" (trace fossils are not to be named as substitutes for their producers), then the traces could be assigned to Rusophycus/Cruziana on their form alone, regardless of what created them (perhaps some other arthropods: shrimp, notostracans?).

    Browsing through the Treatise volume on trace fossils (Hantzschel, 1975), there are several ichnogenera that are superficially similar in form (Isopodichnus, Kingella, Ixalichnus), all of which are attributed to resting traces or trails of arthropods.

    Nice blog, BTW!

    --Howard Allen (U of C alum from a long time ago!)

  4. Thanks for the comments Howard. I hadn't heard the original German phrase before, but the concept does make sense. Now I'll be searching the literature to see if anyone has found arthropod fossils in the Nordegg Formation...