Crinoid Holdfasts

It is a busy week, so a quick post to show a few different crinoid holdfasts from the Ordovician of Central Kentucky.

This first one was recovered from a mud mound in the Tanglewood mb. of the Lexington Limestone in Fayette Co Ky. This outcrop is strange in that the Tanglewood is a calcarenite that was deposited above wave base, and has many local unconformities. As such, the fossils are generally broken and abraded.

At this locality, there is a mud bed that is of limited lateral extent(a few meters) that has produced numerous(about 50) Pychnocrinus sp and Archaeocrinus sp. About the only other fossils found in the bed are bryozoans, an occasional gastropod(Cyclonema varicsosum), and some scolecodonts. I’ll present those in the future.

Perhaps, it was a lagoon, or channel, that protected the community from currents and waves???

Notice the pinnate structure. There might be more to this one.

Close up of above.

Curiously, quite a few of the crinoids from the site are missing the calyx.

In Franklin Co Ky, there is another outcrop that has produced about 100 Reteocrinus sp. The bed containing the crinoids is in the Millersburg mb, and about a meter below the contact with Tanglewood. Since the ossicles are of a different shape than the Reteocrinus ossicles, this is probably from a pinnate form that is uncommon at this locality.

scale in cm

.A few crinoids from the outcrop can be seen HERE.

The last two are the ones that I mentioned in this post. They were recovered from the Clays Ferry Fm. in Franklin Co Ky.

The outcrop in which these were found is known to produce several species of crinoids, but I haven’t spent much time in the field, there. Perhaps, this summer?


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