Friday, June 22, 2012

The Eurypterid “Eurypterus remipes” is the Official Fossil of the State of New York: Part II - Fossil Hunting at Lang’s Quarry of Passage Gulf

Interested in details of eurypterid anatomy, evolution and tectonics? Who isn't! Please visit my recent post. Here’s the link:

In 1984, Eurypterus remipes was designated the official fossil of the State of New York, a fitting choice since the majority of the prolific eurypterid-bearing regions of the world are found within the state’s borders.

This ventral view of a eurypterid displays its major body divisions, segmentation, spinose walking legs
and distinctive swimming paddles. Even the minute serrations on its lance-like telson are exquisitely preserved. The fossil is likely a molted exoskeleton rather than a carcass, as the majority likely are.
(Photographed at the R.A. Langheinrich Museum)

Eurypterids are commonly known as “sea scorpions” due to their striking resemblance to terrestrial scorpions, not surprising since the two belong to phylogenetically-related sister groups (Eurypterida and Arachnida). Eurypterids were marine members of the arthropod phylum from the Early Ordovician through their ultimate demise during the great Permian extinction with their heyday during the Silurian.

(Source unknown)

Eurypterids were not only the largest arthropods but thought to represent some of the earliest animals to undertake brief amphibious excursions onto land (Selden, 1985; Braddy, 2001). Their arthropodal body architecture made them pre-adapted for adventuring landward with exoskeletons that provided support and water conservation capabilities, flexible legs for walking on land and a respiratory system adaptable to breathing air. Eurypterids never transitioned to a fully land-based lifestyle having gone extinct 250 million years ago, but their phylogenetic relatives certainly did, the closest of which are arachnids (scorpions, spiders, ticks and mites).

About 420 million years, plants such as Cooksonia began their conquest of the land, followed soon by animals such as eurypterids. They were opportunists in that they took advantage of what they already had, body parts and behavior adapted to an aquatic existence but useful on land as well.
(Model on display in Smithsonian Institution’s Natural History Museum)

Phylum Arthropoda > Subphylum Chelicerata > CLASS MEROSTOMATA > ORDER Eurypterida
Examples of arthropods include insects, horseshoe crabs, lobsters, crabs, centipedes, scorpions, spiders and mites. All are invertebrates (without a backbone) and possess a compartmentalized body (that is segmented), tubular jointed-appendages (a tremendous evolutionary novelty) and a rigid exoskeleton (for protection).

These innovations allowed arthropods to populate almost every ecological nook and cranny on Earth in immense numbers. Some 80% of all known animal species are arthropods, mostly insects. That led the Harvard paleontologist Stephen Jay Gould in Wonderful Life to refer to the Cenozoic Era as the “Age of Arthropods” rather than the egocentric “Age of Mammals.”

Eurypterids were also chelicerates, an arthropod subphylum, along with horseshoe crabs, spiders, mites and scorpions, named as such for the chelicera, the distinctive first appendage in front of the mouth. Arachnids, the chelicerate sister group, includes spiders, scorpions, ticks and mites.

The general public has the perception that fossils are extremely rare. They don’t know where to look for them (except within a display case or a "dusty" museum) or even what they look like when found. But as we all know, fossils are extremely common. The preservation of past life, which is what fossils are, requires a convergence of opportune circumstances that allows their rocky interment. The process of their preservation is called “taphonomy.”

Biomineralized bones and shells are favored for perpetuation over fragile soft tissues, as are large bones over smaller ones. Rapid burial increases the chances of preservation from bacterial decomposition, tissue degradation, scattering and scavenging. Diagenesis and pyritization enhances the fossilization of delicate structures. If the taphonomy is favorable, the fossil record provides us with a “story of the past that is written in stone.”

Under the best of circumstances, only 15% of plants and animals become immortalized as fossils. In 1859, Charles Darwin made this observation in Chapter 9 of On the Origin of Species entitled “On the Imperfection of the Fossil Record.” Darwin was concerned that its imperfection would discredit his theory of evolution.

On special occasions the fossil record may present us with an astounding and rare gift. Fortuitous circumstances may allow the preservation of fossils in either vast numbers or exceptional quality, or both. Paleontologists call such a taphonymous discovery “lagerstätten”, a German word meaning “storage place.” Think of it as a fossil-mother lode.

There are many fossil lagerstätten scattered around the world. In New York State there are three. One is the “Bertie Waterlime” special for its abundance of eurypterids. Two are nearby to the east: the Middle Ordovician Walcott-Rust Quarry (about 485 Ma) and the Late Ordovician Beecher’s Trilobite Bed (about 445 Ma), both renowned for their remarkable preservation of trilobites, also extinct arthropods of the Paleozoic seas. 

A Pterygotid eurypterid grasping its next meal
(Source unknown)

By the Late Ordovician, eurypterids were present in shallow marine settings in Laurentia (see my post Part I for a tectonic explanation). By the Silurian and into the Devonian, they were thriving in restricted, near-shore environments primarily within the “Bertie Waterlimes.” Waterlime is an industrial rather than a geological term, so called because of its ability to set as a cement under water.

Waterlimes are deposits found in New York State within the Salina Group and largely within the overlying Bertie Group. Their deposits are characteristic of shallow-water basins with a restricted circulation and typical of the arid climate of the New York region of Laurentia during the Late Silurian at about 30°south of the equator. The eurypterid-bearing sequences of the waterlimes crop out along a long swatch of Late Silurian to Early Devonian real estate from eastern Central New York somewhat into Canada.

The Bertie Group (the type locality is a Canadian township) is a carbonate sequence of dolostones and limestones with minor shale and mudstone units, evaporites (of gypsum, halite and anhydrite) and intercalated waterlimes that accumulated during multiple oscillations of the Silurian seas. Amongst the numerous waterlime horizons that exist within the Bertie, several species of eurypterid remains have been recovered predominantly within the Phelps Waterlime Member (notably E. remipes) of the Fiddlers Green Formation (a major transgressive-regressive cycle) and the earlier Williamsville Formation (notably E. lacustris) of western New York and the Niagara Peninsula of Ontario, Canada. Eurypterids are also found in southeastern New York within the localized Shawangunk Formation. Unconformably overlying the Bertie Group are Lower Devonian eurypterid-bearing carbonates (of genus Erieopterus).

Eight different onshore to offshore paleo-environments are recognized within the Bertie Group including sabkha, hypersaline lakes, assorted tidal, lagoon and estuarine (Hamell, 1985).

Late Silurian Salina and Bertie Groups (light gray on upper inset) form an outcrop belt that extends from east Central New York across the state to Buffalo and into the Niagara Peninsula of Ontario, Canada. The Passage Gulf locality is situated at the outcrop’s easternmost extent (stratigraphy lower right). Within the Bertie Group, the productive eurypterid-bearing waterlime is the Phelps Member of the Fiddlers Green Formation.
 (Modified from Tetlie et al, 2007)

Nestled along the Mohawk River and the famous Erie Canal that flow eastward across the state is the sleepy eastern Central New York town of Ilion. A stone’s throw from town in the hills to the south amongst picturesque pastures and woodlands is a nondescript 1950’s roadcut known as Passage Gulf whose singularity is easy to overlook.

Passage Gulf’s main attraction are the exquisite eurypterid fossils preserved within exposures of the Phelps Waterlime at its eastern extent. Heading west across the state, the waterlimes crop out in roadcuts, ravines, creek beds, canal beds, building excavations and quarries, exposing eurypterid material that is there if you’ve got the patience and skill to find it. A master at his trade, paleontologist Sam J. Ciurca, Jr. has been doing just that for over 50 years and mapping the stratigraphy as well.

Sam J. Ciurca, Jr. in 1965 with a four-foot ‘monster’ Pterygotid (Acutiramus macrophthalmus)
(From and Eurypterids Illustrated)

Within sight of Passage Gulf is Lang’s Quarry. Allan and Iris Lang have been excavating, preparing and displaying eurypterids, lecturing to and hosting school groups, paleontological societies and scientific institutions both locally and from around the world since their establishment was founded in 1984.

On a crisp, sunny April day, Allan Lang gave me a private tour of his quarry. With me bouncing around on the back of his all-terrain vehicle, we sped off climbing the well-worn, gravelly dirt trail behind the museum. As we ascended the slope, deer clambered left and right to get out of our way. In under a minute we were in the quarry. Allan enthusiastically explained his modus operandi for retrieving fossil eurypterids, an arduous and patience-testing task that he’s been performing with a labor of love for almost 30 years.

After several feet of overburden consisting of unconsolidated Pleistocene glacial till and topsoil have been removed, heavy earth-moving equipment is used to exhume the underlying Fiddler’s Green Formation. The target is the 1 to 1.5 meter thick, fossil-bearing waterlime of the Phelps Member. The excavated rock face in the photo provides a scale of the excavating operation.

Rather than hack away at the dense dolostone by hand, a laborious and time-consuming process, extracted large blocks are allowed to weather a series of harsh Central New York winters (of which I can testify to having grown up in nearby Syracuse). Assisted by winter’s repetitive freezing and thawing, the rock tends to readily cleave along frost planes that have developed.

Once the rock has fully weathered, the seasoned waterlime is ready. Notice the two “foreign” boulders of glacial erratic amongst the talus of waterlime. Allan is hard at work doing what he both loves and knows best.

Allan instructs that by aligning a hammer and chisel at the right angle within a frost plane and followed by a lot of pounding the dolostone will split apart. Notice the fine-grained, layered nature of the waterlime’s limy muds.

Finally, a firm, two-handed pull lifts the heavy, newly exfoliated façade and exposes the treasures that have been trapped for over 400 million years. Seeing my enthusiasm, Allan cautioned that typically hundreds of slabs must be split apart in order to find one good eurypterid. Unknowingly, I was about to defy those odds.

Call it beginner’s luck, but on my first attempt I uncovered a massive, foot-long claw from the eurypterid Pterygotus! This was the portion of the claw attached to the head structure, referred to as a fixed ramus, whereas the movable grasping-end is the free ramus. Together they clamp down on the eurypterid’s prey similar to a lobster-claw. Based on the size of the claw, my guess for the Pterygotus was 6-8 feet in length.

Still partially buried within the matrix of the waterlime, the claw’s massive teeth are readily discernible.

 (Modified from an illustration by William L. Parsons, Buffalo Museum of Science)

On my second slab-splitting attempt, I uncovered two small molts of Eurypterus eurypterids. Allan marks noteworthy fossils with yellow chalk. They will eventually be transported down to his lab where they are carefully excised from the matrix of the waterlime, cleaned and professionally prepared with micro-air abrasion, a laborious and skill-requiring process.

Notice the conchoidal fractures in the waterlime that cleaves similar to a broken soda bottle. Allan refers to their appearance as “dishes.” Conchoidal fractures transect more than one bedding plane and often contain eurypterid fossils. In all, we sectioned three or four slabs.

This is a close-up of the newly-exposed veneer of waterlime seen above. Seen from the ventral aspect, two Eurypterus remipes are seeing the light of day for the better part of 415 million years.   

After my rewarding visit to the quarry, we headed back down to the museum. I was anxious to see what surprises Allan had unearthed over the years. Please see my next post Part III – The R.A. Langheinrich Museum of Paleontology.

The Lang’s facility is open by appointment only. Contact information is available on their website. 

Distribution and Dispersal History of Eurypterida (Chelicerata) by O. Erik Tetlie, 2007.
Testing the Mass-Moult-Mate Hypothesis of Eurypterid Paleoecology by Matthew B. Vrazo and Simon Braddy, 2011.
The Eurypterida of New York VI by Clarke and Ruedemann, 1912.
The Rise and Fall of the Taconic Mountains
by Donald Fisher, 2006.
Geology of New York by Y.W. Isaachsen et al, 2000.
The Trilobites of New York
by Thomas E. Whiteley, 2002.
Eurypterids Illustrated by Samuel J. Ciurca, Jr., 2008-2010.
Fieldtrip Guidebook, NYS Geological Association, Fiftieth Annual Meeting (1978), Fifty-fourth (1982), Sixty-second (1990), Sixty-sixth (1994) for publications by Samuel J. Ciurca, Jr.

SUGGESTED WEBSITES and by Samuel J. Ciurca, Jr. by Allan and Iris Lang

I wish to thank Allan and Iris Lang for their time and generosity in making their incredible collection at the museum available for viewing and photography. I also want to thank Allan for his private tour of the quarry.

Many thanks also to paleontologist Samuel J. Ciurca, Jr. of Rochester, New York for his personal communications. Sam has been studying, collecting, meticulously documenting and publishing on eurypterids, their associated flora and fauna, and the entombing stratigraphy for over 50 years. He has donated thousands of specimens from his personal collection to institutions such as the Yale Peabody Museum’s Division of Invertebrate Paleontology recognized as the Ciurca Collection, the Smithsonian Institution and the Buffalo Museum of Science.

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