Eurypterids
Specimen of the Month
Samuel J. Ciurca, Jr., Rochester, New York          by Eurypterids.net
JULY 2009
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ABOVE: The Williamsville Waterlime,
(Late Silurian Bertie Group) is a very re-
sistant, fine-grained dolostone and is
the repository of countless eurypterid
specimens. Unfortunately, it is rarely ex-
posed natually and when encountered in
a quarry is relatively difficult to work.
When fresh, the eurypterid-bearing beds
are about 18 - 24 inches thick in one
solid mass. A little weathering, however,
begins to weaken the layers and the
rock can begin to be split. In the photo
above, an eurypterid collector takes ad-
vantage of natural joints in the strata and
works his way into the beds - notice the
narrow block of waterlime he has just re-
moved. Shortly after I took this photo, an
euryptrid was encountered and the prob-
lem of extricating the animal from the
rock, began.
Collectors try to remove a specimen as
best they can, but the way waterlime
often breaks causes many problems in
recovery. Waterlimes are brittle and
usually exhibit conchoidal fracture.
Anatomy of a 'Dig'
PROFILE: A FOSSIL COLLECTOR SHOWS HIS SKILL!
(Tod Clements of Rochester, New York)
MORE EURYPTERID OF THE MONTH PAGES  
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ABOVE: The waterlime splits easily when weathered to a certain degree. When fresh, it is
difficult to break on a bedding plane. Most pieces bear nothing or a few fragments of fossils.
Here Tod has split a large slab (and see below) that had nothing of note.  
BELOW: After several hours of removing
slabs of the waterlime, Tod encountered
a portion of the eurypterid,
Eurypterus
lacustris
. We obtained orientation data
as part of an ongoing study of the paleo-
ecology of the eurypterids within Bertie
Group strata.
In order to recover as much of the
specimen as possible, Tod took to his
saw. By carefully sawing out the speci-
men in a rectangular block, (see photo)
it was hoped that the block could be
freed from the bedrock and that, later,
the animal could be exposed. At this
point, there was no assurance that the
entire eurypterid would be preserved
beneath the matrix.
Note that parts of the swimming legs are
evident, the eyes are prominately
displayed and that the specimen is dor-
sal up.
LEFT: After removing the overlying matrix, it was discovered that the
specimen was not quite complete. Nevertheless, it is a great fossil
specimen. The lines drawn on the slab of waterlime mark where the
slab is to be cut. Below is a closer view, Note that some of the matrix
was so fused to part of the fossil that it had to be cut/chiseled to fully
expose the swimming legs.
BELOW:  Note the preservation of the spiny walking leg
and another longer leg. Broken pieces of the swimming
leg had to be glued back in place. The shiny, reddish areas
are the integument that remained with the specimen, much
of it disintegrated and is not preserved on this specimen -
it flakes away and sometimes is even blown away by any
wind that may be present. From finding the fossil, to re-
vealing all that is preserved can be quite a task. This spec-
imen will be preserved (reposited) within the Yale Peabody
Museum of Natural History.
The Buffalo Museum of Science has a large collection of
specimens of
Eurypterus lacustris, and specimens are
found in museums around the world.
Eurypterus lacustris Harlan was one beautiful creature, for an
arthropod, and has fascinated collectors for over 150 years.
It, along with its precursor (
Eurypterus remipes), has been
studied in extraordinary detail yet is still the subject of much
research among 'eurypteridologists' - we still do not know
exactly how and where these most common of eurypterids
lived. For a recent discussion of "Ecdysis in sea scorpions
(Chelicerata: Eurypterids)" see Tetlie, Brandt, Briggs:
Palaeogeography, Palaeoclimatoogy, Palaeoecology 265
(2008) 182-194.