Ordovician Trepostomate

While visiting a friend’s(Herb) house, I noticed a stone that he had placed at the down spout of his gutter. Well, actually his father had placed it there many years ago in an attempt to inhibit erosion by allowing the energy from the falling water to dissipate at the surface of the stone.

The stone was placed in its location in the 50s or 60s, and the falling water, over the years, had exposed multiple “tips” of some kind of stony bryozoan. The bryozoan had been preserved as silica replacement in a bed of a muddy carbonate.

Herb knew of my enthusiasm for inverts, and when he noticed my pre-occupation with the “dissipation stone”, he ask if I wanted it!

Upon getting the rock home, I treated it with multiple baths of HCl to reveal the colony within… and a splendid colony, it was.

Trepostomate bryozoans can be particularly hard to ID without a thin section and intimate knowledge of the subject. And, I don’t have either, but the results are stunning.

It is probably some kind of calloporid.

Sorry, I don’t have a before pic and the finish is out of focus, but you get the ideal.

Since the rock was retrieved from the Kentucky River Valley near Frankfort, it is probably from the High Bridge Group; more than likely the Oregon Fm or Tyrone Fm.

EDIT:I am experiencing some kind of scripting error, so this is an off-site link.


EDIT: The scale is in inches(2.54cm/inch). Its a whopper!


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6 Responses to “Ordovician Trepostomate”

  1. Dave Says:

    Wow! What a great fossil and the fact that it’s intact and not shattered in a million pieces is just great. Is the silica preservation common from the formations it was found in? I want my own chunk of rock to etch out now! 😦

  2. Solius Symbiosus Says:

    To be truthful, Dave, I am unsure of the formation, since it was float. Originally, I thought that it was from the upper High Bridge Group, but after some thought, the lithology probably better resembles lower Lexington Lm.

    Locally, there are several members and formations that preserve fossils as silica.

    I have some nice silicified Loxoplocus that I collected for Nick, somewhere. I’ll put those up sometime in the future.

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