>Dear all, I have recently been doing some fossiling up here in
>Columbus, Ohio, and I need some help. The other day I broke open a rock
>with sponge fossils all over it, and inside was a lot of deeply grooved,
>clam looking
>things...................
>
>Thanks,
>James
 
James,
 
I think the "sponge" fossils you are finding are probably coral or bryozoan
fossils. Sponge fossils are extremely rare because they had no hard parts
to protect them long enough for them to fossilize.
 
The other fossils you are finding are indeed lamp shells, or brachiopods
(Phylum Brachiopoda).  The time that the land around Columbus was created
(by deposits from a shallow sea) was the Paleozoic, more specifically the
Devonian,  (really roughly,  350 - 400 million years ago -- don't hold me
to dates--they seem to change from book to book as science processes more
information about them.)  During the Paleozoic, from the Ordovician on, the
brachiopods were the most abundant animals of all.
 
Most of them didn't move around much, but lived their lives attached by a
stalk that came out of a hole in the beak or hinge area of the shell, the
other end of which was firmly attached to the substrate. Some were not
attached to the bottom, but burrowed in the sand instead.
 
You are right, they look a lot like cockles, but they have a top (dorsal)
valve and a bottom (ventral) valve instead of a right and a left valve like
bivalves do.  And the valves are always unequal in size, the smaller valve
being the dorsal valve. The ventral valve usually extends beyond the hinge
line while the dorsal valve ends there.
 
 Another visible difference is that hole for the stalk to exit the shell.
If you are wondering which is top and which is bottom, the valve that has
the hole or notch through which the stalk exits is the ventral valve. Some
don't have this hole or groove in the ventral valve though...those are the
sand burrowers.
 
The top or dorsal valve has an internal support for the feeding organ, a
pair of arm-like structures called the lophopore or the brachia (arms), the
latter being the source of the name "Brachiopoda." Mostly they ate bits of
organic matter from the ocean floor, sweeping the food into their body with
those "arms."
 
The little "pecten" you found is probably another kind of brachiopod.  (I
don't think pectens had evolved at that time.) There were very many genera
and species of brachiopods, and they were almost as varied in shape as our
bivalves. Some were fat and rounded or egg-shaped and others were almost
flat. There's one that remonds me always of a fossil walnut.  Many have a
radial groove through the center of the dorsal valve with a corresponding
ridge on the ventral valve. Most of them have radial sculpture. Some have
greatly exaggerated "wings" or "ears" at the hinge line.
 
Where I live in Kentucky, they are a very common fossil. The Falls of the
Ohio River at Louisville is Devonian also, but a lot of the land around
here is Ordovician, and has even older forms of brachiopods. They are a lot
of fun to collect, but not a lot of fun to identify, at least to the
species level, because they seem to change a lot over time.
 
Modern brachiopods are usually called lamp shells because of the shape and
the hole for the pedicle or stalk to come through. It makes some species of
brachiopods resemble one of those old lamps you rub to get the genie to
come out.
 
Brachiopods were once inhabitants of sunlit shallow seas, but the
relatively few species remaining tiday are often dwellers of deep cold dark
waters. However, Jack Rudloe, in his book, The Erotic Ocean (1971) (p.
228),  tells how to collect a common brachiopod in the Gulf of Mexico. He
says it occurs from Tampa Bay to Pensacola, so you live in its territory.
It is Glottidia pyramidata and it lives on the flats and can most
frequently be found in abundance in the winter. He says, "When you come to
a flat and see small slits everywhere looking as though someone had taken a
penknife and stabbed deeply into the sand and grass, then you know you have
hit brachiopods. Digging alongside the slit with a shovel you pry up a
clump of grass, and if you break the slit along the side, splitting the
slit, you will see the brachiopod exposed. It will immediately contract
down into its burrow, but it is easy to pull it free."
 
He cautions to be careful lest you break the pedicle and he has more on
preserving these animals.
 
Lynn Scheu
Louisville, KY
[log in to unmask]
Don't miss the field trip to the Falls of the Ohio museum and park when you
come to the COA Convention in Louisville in June!