Some of the younger members of our group.
Some of the younger members of our group.
The Dry Dredgers return to a site we have not visited on a field trip since May 1997. It's a road cut near Brookville Lake, Indiana that exposes the Liberty formation, which is part of the upper Ordovician strata of the Cincinnatian Series of formations.
The site have evolved. In the 90's, it was a great site where more than 6 kinds of crinoids have been found. But now, one side has been resurfaced and sodded. The other side is picked over and is all "float" (material fallen from higher up the cut).
Fossils Found that Day
Crinoids
At least a couple of calyxes of Cincinnaticrinus pentagonus were found (next 2 pics)
Another interesting find was a two separate examples of the
anal sac from Plicodendocrinus casei encased
in matrix.
Quite a few examples of crinoid arms and calyxes in matrix were found that don't show quite enough for identification. (next 4 pics)
But lots of crinoid stems were found.
Here's an interesting crinoid stem on matrix that not only is
a cross section showing internal parts, but extends down and shows the holdfast
where the crinoid fastened itself to the sea floor. Nice!
Trilobites
By far, the most common trilobite found that day was Flexicalymene
retrorsa. Some may have been of the subspecies minuens. As
shown in the 8 photos below, most were enrolled but some were prone (stretched
out).
A more rare trilobite that was found were these fragments of Acidaspis
cincinnatiensis. Note the spines on the pygidium (first photo) and
the genal area (second photo).
Also, lots of fragments of the very large trilobite Isotelus were found.
This first photo looks mysterious. It looks somewhat like a
variety of exciting and rare Cincinnatian fossils. But closer examination reveals
that it is a fragment of Isotelus.
Close examination of the surface of Isotelus fragments can reveal contour lines that are diagnostic of the specific trilobite. The specimen below (2 pics) is a genal area leading to the genal spine which is missing from this example of Isotelus.
At least one almost complete pygidium (tail section) of an
Isotelus was found.
Mostly, though, fragments on the surface of rocks were
everywhere on the site.
Corals
The most interesting coral I saw that day was a tabulate coral.
There were lots of examples of an encrusting coral called Proterea
richmondensis.
The most common coral was the large horn coral (solitary
coral) Grewingkia.
Another type of horn coral found was the smaller attaching
coral, Streptelasma.
This can be distinguished from Grewingkia by the opening that
"bells" out more and the tip at the other end is flatter and bent
because it attached to something hard.
Articulate Brachiopods
Thousands and thousands of the the small
brachiopod Cincinnetina
(or Cincinnetina) were found on the surface of slabs.
Cincinnetina were found loose from the rock also. The species
for these upper Richmondian Cincinnetina is currently being
discussed among the Dry Dredgers. The documentation refers to them as meeki
for the entire Richmondian. But it is becoming clear that other species may
exist. In the world of Cincinnati fossils, even amateurs can discover and name
new species.
An interesting brachiopod that is common to the Richmondian
formations but largely absent from the Maysvillian formations is Leptaena.
Good quantities were found on this site.
Even more common was the ubiquitous articulate Strophomenid
brachiopod, Rafinesquina.
Another abundant Strophomenid brachiopod found was Strophomena.
A someone less common Strophomenid brachiopod found was
Eochonetes.
Two very similar Orthid brachiopods found were Plaesiomys and Glyptorthis
This first group of specimens (3 pics) look more like Plaesiomys. One valve is much flatter than the other valve. The sulcus is almost absent, compared to Glyptorthis. Plaesiomys also has a more rectangular outline.
Glyptorthis have two valves that are more similar to each
other in how convex they are. The sulcus is deeper than Plaesiomys.
Here's a batch where the two specimens on the right are more
similar to Glyptorthis. Note the sulcus and more rounded outline. Note also a
"herring bone" pattern to the growth lines on the specimen on the
right. This can also distinguish it from Plaesiomys.
The batch below is more like Plaesiomys. Note the more
rectangular outline.
Another similar brachiopod to the Plaesiomys and
Glyptorthis is Hebertella.
Hebertella are most easily identified by a triangular pedicle opening and a
deaper sulcus than Glyptorthis. For a glossary of brachiopod anatomy, see our Brachiopod
Page.
At least a couple of species of the brachiopod Vinlandostrophia
were found.
And huge quantities of the Rhynchonellid brachiopod Lepidocyclus
were also found. Note the "herring bone" pattern on the first specimen
pictured below. This is an easy way to distinguish it from Vinlandostrophia.
Another way is that Lepidocyclus and Hiscobeccus
have a more rounded profile than Vinlandostrophia.
Inarticulate Brachiopods
Attached to the articulate brachiopods are inarticulate brachiopods. There were many genera found that day.
First we found the very common inarticulate, Petrocrania
scabiosa.
Another inarticulate brachiopod found was Philhedra
laelia.
And a third type of inarticulate Brachiopod found was Trematis.
Pelecypods (Bivalves or Clams)
Harder to identify bivalves
This next internal mold of a clam has a worm tube attached to
it. The position of the worm tube on the clam may give us a clue as to the life
position of the clam.
This next specimen found that day is a mystery. When I
photographed it, I was interested in the honeycomb pattern on the right,
suspecting it could be the algae Cyclocrinites. Now that I'm looking at the
photo, I'm interested in the whole specimen. It may be a clam or possible
something more interesting. I did not record whose specimen this was. So if this
is your specimen, please email me (Bill Heimbrock) at admin@drydredgers.org.
You may have something nice here.
Gastropods (Snails)
Cyclonema
Monoplacophorans
Ichnofossils (traces)
Nautiloid Cephalopods
That's all for this field trip. Now let's continue with photos of the April 2011 field trip.
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