by Zarko Ljuboja

By definition, Eurypterids are terrestrial and aquatic arthropods with a pair of preoral appendages located on the ventral side of the cephalothorax orprosoma. The extraordinary completeness and richness of this fossil in the upper Silurian "Eurypterid Beds" began to unfold when the first specimen was found from Westmoreland, Oneida County, New York. In 1818 Dr. S.L. Mitchill incorrectly described this eurypterus as a 'fossil fish' of the genus Silurus; an error obviously induced by the catfish-like appearance of the incomplete carapace. In 1825, James DeKay recognized the arthropod nature of this fossil, for which he erected the genus Eurypterus and termed the species remipes. Eurypterids belong to the subphylum Chelicerata, of the class Merostomata (Dana 1852), Subclass Eurypterida (Burmeister 1843),Superfamily Eurypteracea (Burmeister 1845), and Superfamily Stylonuracea (Diener 1924).


Their bodies are divided into three segments: the prosoma, the preabdomen or mesosoma and the postabdomen or metasoma. The mesosoma is composed of 6 tergites on the dorsal side and five sternites on the ventral side; the metasoma is composed of 6 caudal or post abdominal segments and a telson (approximately equal to in length of the last 4 segments). The subphylum comprises the classes merostomata (Cambrian to recent) and arachnida (Silurian to recent). Where as the merostomes are aquatic forms, the arachnids are confined to land except for a few forms which are secondarily adapted to living in the water. It was proposed by Clarke and Ruedemann that these were one of the first animals to venture up on land.

The different modes of life have significantly influenced the development of several morphological structures, especially the appendages (walking and swimming legs) and respiratory organs (gills and lungs). Since fossil chelicerates are comparatively rare, our knowledge of the vertical and horizontal distribution of species is fairly limited.


As for horizontal distribution, merostomes are known from North and South America, Europe, Africa, Asia, Russia and Australia, though more frequently in the northern rather than the Southern hemisphere. Up to now fossil arachnids have been found almost exclusively in Europe and North America. Anyone who has collected a fossil locality or a specific formation for a long time, really gets to see some of the splendid varieties of fauna and flora that can be brought to light. Some of these localities are considered to be sparse of fossils or producing only one or two types and nothing else. This is the case of many of the exposures of the Silurian dolostones of the Niagara escarpment; but a few localities where the habitat of the eurypterida is preserved in the Bertie waterlime some of the most spectacularly preserved specimens can be found. The beds of the waterlime have for over 40 years yielded many very prized and splendid examples of Eurypterus, Pterygotus, Dolichopterus, a number of plants, algae, graptolites, ostracods, cephalopods, and phyllocarids. Many known only through their respective fragmentary remains, have been found and described by ardent amateurs and professionals alike over the years.

The two most famous "eurypterid pools" in New York are located in the Buffalo area and in southern Herkimer county. No doubt these colonies were in part breeding pools, or close to them, from brackish to fresh waters closely associated with lagoonal and lacustrine environments prevalent at that time. It was concluded by OÌConnell (1916) that "the eurypterids throughout their phyllogenetic history lived in the rivers". Others have proposed a more varied intertidal environment as the primary habitat of the eurypterids.

As seen in central New York the underlying Camillus shales were deposited in shallow lagoons and extensive playa lakes and sabkha-like environments, with occasional influx of sea water to which lime muds were added by streams draining areas of eroding limestone throughout the New York-Ohio-Pennsylvania and the Michigan-Ohio basins, leading to the environment that the Bertie waterlime was deposited in and the extraordinary preservation of Eurypterids and its associated faunas. These lagoonal and playa lake conditions are exemplified by the presence of mud cracks (in the layers just above and below the eurypterid layer) , salt hopper drag marks, cross laminations and small channels being present in the layer ( including a track way layer between the layer and the overlying mud cracks. This and the presence of Eurypterids, ostracods, Cooksonia (the earliest vascular plant), woody fragments, algal bodies, jellyfish and the absence of other arthropods, pelecypods and mollusca would indicate that the waters in all were shallow and very extensive. Ruedemann believed that " while the Bertie waterlime does not contain atypical marine fauna, the scarcity of forms may be due to the early and complete dissolution of the aragonite shell in the dolomitic mud". This suggests that the Bertie was deposited in a lagoon behind barriers and coral reefs that were subjected to progressive deepening of the water. To date evidence suggests that eurypterids inhabited an inter-tidal environment ranging from just above high tide to a depth between the shore at low tide and about 50 meters or less. They probably lived in a restricted environment such as shallow lagoons with one or two tidal channels or breaches through a reef or barrier bar to the sea and through the inland boundary of the lagoon being associated with swamp areas and flats of an inland deltaic basin system. My opinion is that where these fossils have been found, the water could not have been more than one 1 (3 feet) deep.

I reached this conclusion after extensive excursions and working the area. The locality that I am most familiar with is in southern Herkimer County at a road cut called Passage Gulf (and a private quarry owned by Allan Lang); here exposures of the Phelps waterlime provide some of the most exquisite eurypterid (and associated faunal) remains. It was the construction of a road up the sides of a glacial valley that exposed the Fiddlers Green formation in the early 1950's, since then many spectacular specimens have been collected. Unfortunately due to the limited extent of the roadcut and steepness of the sides, collecting is very difficult.

In 1984 Allan Lang, who purchased a property in an adjacent creek to collect these wonderful fossil creatures, began enlarging the exposure of the Fiddlers Green formation—specifically exposing the Phelps waterlime to an extent that has never been seen, and in which some of the world's rarest fossils have been preserved. My first trip to the quarry was by Alan's invitation back in 1986, when for the first time I'd excavated, collected , studied and prepared the eurypterid fauna of this New York state formation. To my delight, I subsequently experienced firsthand the opening of a few pages of a late Silurian benthic environment in the Herkimer pool.

Since it's discovery, many spectacular specimens of Eurypterus have been found, with sizes ranging from 8 mm (.3 inches) up to 28 cm (11 inches), with Pterygotus ranging from 7.5 cm (3in.) to well over 1 meter ( 3 feet plus), with some body parts found that would indicate a creature of about 6.5 feet in length, as well as Dolichopterus (up to 13 In.) and proscorpius ( 1 - 2 in.), including a significant number of plants, algae, graptolites, phyllocarids, ostracods, medusae, orthoceras, cephalopods, possibly a millipede, and many other unidentified specimens. The fossils themselves are preserved in the lower 2-3 feet of the Phelps waterlime and found in "windrows" —which are actually very shallow, elongated troughs 3 inches to over 3 feet wide and five or more feet long in dolomitic muds of the lagoonal seas prevalent along what is now New York and Ontario.

In general, the Bertie formation of New York and Ontario is a very hard dolomite of the quality that enables farm fences and foundations to last for centuries. Many localities produce eurypterid parts like swimming paddles, heads, tergites, and telsons that are fascinating to find—along with the chance to find a complete specimen. A few formations that have an abundant variety of Silurian fossils are the Ermosa, Bertie or Bass Island formations of Ontario , along with the Shawangunk grit and the Bertie or Schenectady of New York.


Clarke, J.M., & Ruedemann, Rudolf. 1912. The Eurypterida of New York. New York State Museum, Memoir 14, 2 volumes

OÌConnell, M. 1916. The habitat of the Eurypterida. Bulletin of the Buffalo Society of Natural Sciences. Volume 11 No. 3

Copeland, M.J. & Bolton, T.E. 1985. Fossils of Ontario. Royal Ontario Museum. The Eurypterids and Phyllocarids.

Clarke. J.M. 1919. New Paleozoic Crustaceans and a Recurrent Pittsford (Salina) Fauna. New York State Museum, Bull., pt. 3.

Dale N.C. 1953. Geology of the Oriskany (Rome) Quadrangle. New York State Museum, Bull. 345.

Bassler, R.D. 1909. Dendroid Graptolites of the Niagran Dolomites at Hamilton, Ontario. United States National Museum, Bull. 65.

Newland, D.H. 1933. Paleozoic Stratigraphy of New York. Guidebook:4., Excursion A-4.

White, D. 1902. A Description of a Fossil Alga from the Chemung of New York. Report of the New York State Paleontologist. 1901.

White, D. 1901. Two new species of alga of the Genus Buthotrepis, from the Upper Silurian of Indiana. Proceedings of the United States National Museum. Vol. XXIV- no. 1255.

Moore, R.C. 1955. Treatise on Invertebrate Paleontology. Pt. P., Arthropoda

Tollerton, V. 1989. Morphology, taxonomy & Classification of the Order Eurypterida. Burmeister, 1843. Journal of Paleontology, Vol. 63. no. 5.

Penhallow. 1893. Notes on Erian (Devonian) Plants from New York & Pennsylvania. United States National Museum. Vol. XVI. p. 105 - 114. plates IX - XIV.

Ruedemann, Rudolf. 1925. Some Silurian (Ontarian) Faunas from New York State. New York State Museum, Bull. 265. p. 134.

Jones, B. & Kjellesvig-Waering,E.N. March 1985. Upper Silurian Eurypterids from the Leopold Formation, Somerset Island, Arctic, Canada. Journal of Paleontology, Vol. 59. no. 2. p.411 - 417.