Eurypterids - Specimen of the Month
Samuel J. Ciurca, Jr., Rochester, New York by Eurypterids.net
One of the most interesting of the many sedimentary structures found in the eurypterid-bearing dolostones
and black shale beds of the Silurian is the windrow. These wonderful accumulations of eurypterid debris
are sometimes encountered while searching for eurypterid specimens in the Salina and Bertie Groups.
ABOVE: A fine specimen of Eurypterus lacustris Harlan with prolific pieces of eurypterid parts including a
carapace, numerous tergites, swimming leg joints, etc. Note the wrinkling of the thin integument at the
front of the large carapace.
Horizon: Williamsville 'A' Waterlime, Bertie Group, Late Silurian, Fort Erie, Ontario, Canada.
BELOW: An accumulation of Hughmilleria socialis, the eurypterid that characterizes the 'Pittsford Shale.'
Contrast is poor because of 'black on black', i.e. the carbonized eurypterid integument is preserved on the
black shale beds. A rare find of a nearly complete pterygotid occurs at the bottom of the slab. Ciurca and
Tetlie (2007) reported this pterygotid to be Erettopterus osiliensis (Schmidt, 1883) - note the bilobed
telson. It is believed that all of the material on the slab represents molted arthropod remains deposited via
a Silurian storm into shallow, near-shore waters. Small ostracods are present near the middle of the slab.
Ciurca, Samuel, J. Jr. and Tetlie, O. Erik (2007) PTERYGOTIDS (CHELICERATA; EURYPTERIDA) FROM THE SILURIAN VERNON FORMATION OF NEW
YORK, J. Paleont., 81(4), pp. 725-736.
|PHOTO BY TOD S. CLEMENTS - 2010
Note about above specimen: Fine sand and clay covered (was fused) much of the slab and was almost cemented. While much of this has been removed,
the specimen has not yet had a final cleaning. Water cannot be used at all as this will cause rapid disintegration of the rock. When the specimen has been
cleaned as much as possible, a new photograph will replace this image. Data: Specimen collected at the Tasting Site, Monroe Avenue, Pittsford, New York
around 2005. The site was a temporary excavation and is no longer available.
Fiddlers Green Formaton
A third example of an eurypterid windrow is shown below. It is a long and narrow windrow just full of
eurypterid debris with excellent preservation of many arthropod parts. The slab measures 29 by 10.5
inches (about 75 x 27 cm). The specimen is from the famous Herkimer area where many sites have
yielded fine specimens of Eurypterus remipes and associated fauna and flora. Most of the sites are
located around Spoon Hill. A closer view is shown farther down this page and an even closer view
can be seen at the bottom of the page.
You can identify many of the parts that make up the
body plan of an eurypterid in the photo to the right.
Note just to the left of center, a splay of anterior
appendages and locate the mouth surrounded by
the coxae. The large paddlelike appendage is the
Isolated structures in the windrow consist of spines of
the walking legs, a paddle joint, tergites and, just
below the coxae, an operculum with a portion of the
median sex appendage. All of these parts belong to
the common eurypterid, Eurypterus remipes.
The matrix consists of waterlime, a fine-grained
dolostone with conchoidal fracture. It contains some
clay and quartz along with the magnesium carbon-
ate. The origin of waterlime is not known with cer-
tainty. Some consider it a precipitate. It's accumu-
lation may be due to stromatolitic activity in very
shallow waters, the windrows indicating near-shore
settings. Upper beds of the waterlime unit contain
an abundance of mudcracks and sometimes parts of
eurypterids are preserved in the cracks. The Phelps
Waterlime occurs across New York at least to the
area of Victor. The Eurypterus remipes Biota is
probably the best known within the state.