Eurypterids
Specimen of the Month
Samuel J. Ciurca, Jr., Rochester, New York            by Eurypterids.net
FEBRUARY 2009
Rochester Shale Eurypterid
(and some associated fauna)
Counter
The Rochester Formation, commonly referred to as the Rochester Shale, is probably the most fossiliferous Silurian
unit in New York with over 300 species having been described. It is a favorite with collectors and even a commercial
quarry in the shale has been operated for many years near Middleport, New York. The quarry has yielded hundreds
of exceptional fossils, especially trilobites, that have found their way into many collections including museums around
the world. Various lithologies are found within the Rochester Formation including shale/mudstone, bands of fossil-
iferous limestone and particularly hard layers referred to as calcisiltites. Since there has been a plethora of studies
in recent years, there is much published literature available.
ABOVE: A small Dalmanites limulurus trilobite associated with a portion of a large Arctinurus and other pieces of
trilobites and brachiopods. Rochester Formation near Middleport, New York.
BELOW: Another example of characteristic Rochester Shale material, a specimen of a small Bumastus associated
with 'stick' bryozoans - these bryozoans formed thickets on the sea floor and small animals likely hid within the
branches. Rochester Formation near Middleport, New York. Check out a few other examples of fossils from the
Rochester Formation at:  
http://eurypterids.net/RochesterShale.html
A Great Discovery
(serendipity in action)


ADDITIONAL REFERENCES FORTHCOMING
The Rochester Shale is a great marine deposit, over 100 feet thick in some areas east of the type section. One of  
many eager trilobite collectors, Tod Clements, discovered a beautifully preserved carapace of a carcinosomatid, a
type of eurypterid (see below). It is undoubtedly a new species - note the frontal position of the large eyes and the
characteristic ornamentation.
A NEW EURYPTERID (CARCINOSOMATIDAE) FROM THE SILURIAN CLINTON GROUP OF WESTERN
NEW YORK STATE
Samuel J. Ciurca, Jr., O. Erik Tetlie, Rochester Academy of Science Session Abstracts, 31st
Annual Paper Session Monroe Community College and the Natural Science Departments, November 6, 2004, p.4.
While eurypterids are common fossils in the Late Silurian strata of New York (so-called "eurypterid beds"), it is rare to
find them in other formations. Tod Clements donated this exceptional fossil to the Peabody Museum of Natural History
in New Haven, Connecticut where it can be studied and compared with well-known carcinosomatid material from the
Late Silurian Bertie Group. Information on the origin and evolution of these peculiar eurypterids is incomplete and the
specimen will be invaluable to future reseachers studying these aspects of eurypterid paleobiology.
MORE EURYPTERID OF THE MONTH PAGES  
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