Specimen of the Month
Samuel J. Ciurca, Jr., Rochester, New York by Eurypterids.net
|Hughmilleria socialis Plate
SPECIAL SPECIMEN FROM THE 'PITTSFORD SHALE'
(SPECIMEN COLLECTED IN 2003)
In 1903, Clifton Sarle re-
ported the discovery of a
wonderful new eurypterid
fauna in dark shales at
Pittsford, New York (just
southeast of Rochester).
From time-to-time, though
rarely, construction sites
in the area have led to the
rediscovery of the fossil
horizons that produced
the fossils that Sarle had
encountered during his
recovery of fossil speci-
mens as the Erie Canal
At left is a specimen I
removed directly from the
shale horizon in 2003 as
it was exposed during the
construction of a new
shopping site. Most of the
fossil remains on this
plate are of Hughmilleria
socialis, the characteristic
eurypterid found within the
Pittsford Member of the
The slab presents Hughmilleria in dorsal aspect, but the molts were actually preserved dorsal down. It would appear
that a storm brought the remains to their burial site, but in such a way that spiral currents (a gyre) deposited the
molted remains within a shallow depression. Note the well-preserved metastoma (at right) and small coxa (uppermost
portion of the slab) and the many other fragmentary eurypterid remains.
The metastoma is 2.4 cm long, width = 1.4 cm, telson ~ 3.6 cm. The Hughmilleria on the left side: carapace (at base)
is 2.8 cm wide. l = 2.3 cm. The very large tergite on the plate probably belongs to Eurypterus pittsfordensis. Both
Hughmilleria specimens were found dorsal down.
STRATIGRAPHY: Several years after Clifton Sarle's report of a new eurypterid fauna in the "Pittsford Shale" another
horizon was found higher up in the section (the Barge Canal Member of Ciurca, 1990) with abundant Eurypterus
pittsfordensis, but no Hughmilleria. Interestingly, there are now at least six known eurypterid-bearing units within the
Vernon Formation of New York State, and there may be still more. Natural exposures are not known within the type
area of the Pittsford Member (Pittsford, New York). The initial discovery was made because of reconstruction of the
Erie Canal, and all subsequent discoveries have been due to excavation and construction of one kind or another.
In central-eastern New York, natural exposures have yielded eurypterid and fish remains associated with 'Lingula' sp.
and other invertebrates (Downing Brook and Farmers Mills Members).
A stratigraphic section for the type area of the Pittsford Member of the Vernon Formation is described in:
Ciurca & Tetlie, PTERYGOTID (CHELICERATA; EURYPTERIDS) FROM THE SILURIAN VERNON FORMATION OF
NEW YORK, J. Paleontology, 81(4), 2007, pp. 725-736 (and references therein).
CIURCA EURYPTERID COLLECTIONS:
For over 40 years, I have been collecting eurypterids (and associated fauna and flora) and studying the
geographic and stratigraphic distribution of these unusual animals. Most are of Silurian age, but the Early
Devonian is also represented as are some purchased items that cannot easily be collected by someone who lives
in New York State (e.g. Ukraine eurypterids). Lithologies and sedimentary structures are important to our
understanding of the eurypterid biota and many representative samples have also been retrieved and entered
into my collections. Stratigraphic analysis of Late Silurian deposits, in particular, provided for the discovery of new,
previously unknown, eurypterid horizons within a highly populated state - I guess that was the result of not too
many people being interested in relatively 'unfossiliferous' rocks. As is often the case with new discoveries, more
questions were generated than answered. Eventually, however, more answers will become more evident as the
studies evolve - hence, a large portion of my collections is now part of the Peabody Museum of Natural History
(Yale University) in New Haven, Connecticut. Check out: