Eurypterids
Specimen of the Month
Samuel J. Ciurca, Jr., Rochester, New York        by  Eurypterids.net
Erieopterus microphthalmus
Erieopterus is a genus that abruptly appears in the New York and Ontario, Canada stratigraphic sequence when the Early Devonian
(Helderbergian) transgression spread across a Late Silurian evaporite sequence of mostly dolomitic sediments replete with an
Eurypterus fauna. Erieopterus is a widespread eurypterid - it has been found from near Albany, New York (Thacher State Park)
westward into Ontario, Canada (Haggersville). It is particularly common in the Early Devonian strata about Syracuse (Chrysler, Olney
and Thacher Formations).
The specimen shown below was collected from the upper Olney Limestone, Manlius Group, at the Split Rock Quarry just west of
Syracuse, New York. Width of carapace (at base) is 7.5 cm. The specimen is about 23 cm (9 inches) long. This is probably the largest
Erieopterus specimen that has ever been found.
Erieopterus is generally encountered in beds replete with the brachiopod, Howellella vanuxemi and clams. The Manlius Group of
limestones and dolostones is typically a marine sequence with layers of crinoidal and bryozoan debris. Within the lower portions of the
sequence, biostromes and bioherms of a stromatolitic nature are almost ubiquitous. The stratigraphic section exposed along the
highway south of Clockville, New York, illustrates this well.
The areal extent of the occurrence of
Erieopterus is enormous as is the quantity of the remains, some simply littering bedding planes.
Erieopterus has been reported from Michigan (subsurface) eastward through Ontario, Canada, the Bass Islands in Lake Erie, and (as
mentioned above) across New York State to near Albany. Thus far,
Erieopterus has not been reported from Early Devonian rocks in
regions to the south (i.e. Pennsylvania, West Virginia, Maryland).  
AUGUST 2008
EURYPTERIDS.NET
Counter
SJC0001
Erieopterus microphthalmus
(width of carapace = 6 cm)
Upper Olney Limestone
Manlius Group
Split Rock Quarry
near Syracuse, New York

Note abundant brachiopods - they
are ubiquitous:
Howellella vanuxemi
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"Eurypterids Illustrated" The Search for Prehistoric Sea Scorpions
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