|Commentary on a specimen of an Eurypterid
Samuel J. Ciurca, Jr.
Rochester, New York
|Eurypterus lacustris Harlan
Late Silurian, Niagara Peninsula
|Eurypterus lacustris, occurring within the Williamsville Waterlime (exclusively), Bertie Group, Late Silurian of Western New York and adjacent Ontario, Canada (Niagara Peninsula). Width of carapace (at base): 3.6 cm. CIURCA 062604-1A (left) and 062604-1B (right). Note crinkled region on one side of the animal. This is interpreted to be where a strong current 'dumped' the molt. As it entered the sediment, that side became crinkled and it came to rest to be buried in carbonate sediment.|
|AT RIGHT: Enlargement of swimming leg region to show that 3 terminal joints are missing. Note spiny 'walking' legs.
This specimen was found with the molt preserved upsidedown. Thus far, there is no evidence that eurypterids found within the Williamsville Waterlime actually lived in the region in which we find their fossil remains. Even complete specimens are probably just molts washed in from more marine regions that existed to the south and southwest. Obviously, preservation of the speci men depicted here is exceptional. This may be due to hypersalinity. Many of the waterlime units within the Bertie Group give abundant evidence, in the form of SALT HOPPERS, that the environment of deposition was hypersaline. This may have prevented scavenging of even the integumentary material.
Evidence for transportation is almost ubiquitous. While collectors favor the 'complete' specimens, most remains found are disarticulated parts - molts that have been ripped apart during the transportation into nearer shore, pre- sumably lagoonal areas behind 'algal' and/or stromatoporoidal banks.
|Locality: Ridgemount Quarry South, Bertie (now Fort Erie) Township, Ontario, Canada. Horizon: Williamsville Waterlime, Bertie Group.|
|Commentary - Williamsville Waterlime at the Ridgemount Quarry South, Niagara Peninsula, Ontario, Canada|
| The number of eurypterid specimens obtained by collectors from this quarry since it began operation is extrordinary. However, not a lot of useful data have been recorded or published.
The literature is full of papers that imply that eurypterids lived in the environment in which the waterlimes were deposited. I have long insisted that there is much evidence of transportation (abundant fragmentary remains, usually current deposited or sorted, abrasion, ripped integument, cracked integument, and specimens preserved in a great variety of positions within the sediment).
To date, there is no evidence that any 'complete' specimens retrieved are 'cadavers.' Only one specimen I personally collected over many years seemed to indicate that a 'body' may have decomposed before preservation in the limy sediment.
All associated faunal remains also appear to have been transported (cephalopods, brachiopods, clams, horseshoe crabs, plants, etc.). The rare stromatolites that have been observed in this quarry are obviously in situ. And SALT HOPPERS are in situ, even if rare in this particular waterlime unit.
Scavenging of eurypterid integument is apparent on many eurypterid pieces. This could have taken place elsewhere, or within the environment of depostion of the waterlimes by, perhaps, gastropods. High-spired gastropods are exceedingly abundant within the Williamsville Waterlime and often occur in clusters. Additionally, these gastropods are widespread within the Williamsville Waterlime and continue into the more marine limestone units to the east (and probably south).