File:Triarthrus Eatoni (pyritized Fossil Trilobite With Appendages) (Whetstone Gulf Formation, Upper Ordovician; Lewis County, New York State, USA) 3.jpg
The remarkable trilobite shown above is from a lagerstätte - a fossil deposit that has preserved soft parts. One of the most famous lagerstätten in North America is Beecher's Trilobite Bed. It was discovered in the 1890s in dark shales of the Frankfort Shale (Upper Ordovician) northwest of Utica, New York State. Its most notable fossil component is pyritized Triarthrus trilobites with preserved appendages (legs and antennae).
Additional sites and horizons with Beecher's Bed Lagerstätte-type preservation have been identified in upstate New York (see Farrell et al., 2009). The pyritized Triarthrus trilobite shown here is from the Whetstone Gulf Formation (also Upper Ordovician), which consists of mixed marine siliciclastics, but is dominated by fine-grained rocks representing distal turbidites. Reported fossils from the Whetstone Gulf Formation lagerstätte include algae, conulariids, brachiopods, bryozoans, gastropods, ostracods, trilobites, eurypterids, crinoids, graptolites, trace fossils, and inferred coprolites.
Classification: Animalia, Arthropoda, Trilobita, Polymerida, Olenidae
Stratigraphy: Whetstone Gulf Formation, Lorraine Group, Maysvillian Stage, middle Cincinnatian Series, Upper Ordovician
Locality: unrecorded/undisclosed site in Lewis County (probably from the Martin Quarry), northern New York State, USA
Some info. derived from:
Farrell et al. (2009) - Beyond Beecher's Trilobite Bed: widespread pyritization in the Late Ordovician Taconic foreland basin. Geology 37: 907-910.
See info. at: en.wikipedia.org/key/Triarthrus and
en.wikipedia.org/key/Beecher%27s_Trilobite_Bed