Eurypterids
Specimen of the Month
Samuel J. Ciurca, Jr., Rochester, New York         by Eurypterids.net
Acutiramus cummingsi and A. macrophthalmus
ABOVE: (CIURCA 063208-1) Beautifully preserved pincers (rami) of the pterygotid, Acutiramus cummingsi. This
specimen is from the Williamsville 'A' Waterlime, Late Silurian Bertie Group, RQS in Fort Erie Township (Bertie),
Ontario, Canada (specimen has been donated to the Peabody Museum of Natural History at Yale University in New
Haven, Connecticut. The fixed ramus is about 4.8 cm long. While rarely encountered, this pterygotid is known
(mostly from molted parts) from similar rocks as far east as Jamesville, New York. Complete specimens are known,
but extremely rare. Pterygotids punctuate the Late Silurian strata at many intervals within New York State, from near
the base of the Salina Group to the Early Devonian Manlius Group (Helderbergian).
Pterygotids were undoubtedly the 'sharks' of the Siluro-Devonian seas. Their prey could likely have been the
smaller eurypterids, e.g.
Eurypterus, which is preserved in countless numbers in the various units of the Bertie
Group. A wholesome predator/prey ratio exists if this were the case. A streamlined body, large anterior eyes and the
great claws makes for a monstrous, swift and agile predator. It is noteworthy that no remains of 'fish' have been
recorded within our eurypterid-bearing rocks, but the association does occur in other regions and, especially, in
Devonian rocks.
ABOVE: Acutiramus macrophthalmus, the characteristic pterygotid of the Fiddlers Green Formation, Bertie Group
of New York and Ontario, Canada. This is a relatively large fixed ramus (about 18 cm long). The ramus was
transported to the site and likely lost a few teeth on the way. Some specimens are so worn that they resemble a
piece of driftwood more than a ramus. Since rami are thick, reinforced structures, they are more likely to be
preserved, especially if they have been carried shoreward (lagoonward) over long distances.
This specimen was collected at the famous Passage Gulf Site that has yielded hundreds of specimens of various
eurypterid species over the past 50+ years. The nearby commercial Lang Quarry has also provided, since the mid
1980s, abundant remains including many specimens of complete pterygotids.
Also check out:  http://eurypterids.net/Pterygotids.html
OCTOBER 2008
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