Mostly bryos and burrows

It's still a little early to be out and about in the metro rocks and expect good luck (for one thing, the Decorah is still in winter-spring-transition mud mode) or consistent weather, but we're getting close, and sooner than usual. Here's one seasonal photo and then a few interesting pieces I hadn't featured before. These are all photos of Decorah Shale fossils from the St. Paul side of the river.

Lower Decorah a couple of weeks ago, after having been relatively warm and dry for several days. These two fragments were covered with half-burrows (imagine a tubular burrow split along its long axis), and several other pieces from the same area and probably a similar stratigraphic level had the same kind of abundant half-burrows.

A trilobite pygidium in the fork of a bryozoan. Trilobite carapace pieces are sometime found wedged in bryozoan forks, presumably because the trilobite used the bryozoan as a molting aid, but I think that this case is just a coincidence.

A crinoid holdfast. There are some old scientific names for these, but no one uses them anymore.

On the lower right margin of this brachiopod shell (using the photo's orientation) is a tiny holdfast or dwelling tube. It doesn't quite look like Cornulites, but it's the same general concept of a tiny organism using a larger biological object as a foundation.

A "blobozoan", or perhaps a pan flute devised by a stoned nautiloid.

Two good-sized chunks of bifoliate bryozoans. Usually bifoliates are broken up into smaller fragments around here, either shortly after death or when they erode.

This is a fragment of the common local trace fossil known as Rauffella. The lighting highlights the heavily striated surface, which is typical of these fossils. Presumably some surficial feature of the burrower produced the markings (which would be bioglyphs).

A chunk of skooshed orthoconic (straight-shelled) nautiloid.