The Walcott-Rust Quarry: Middle Ordovician trilobite Konservat-Lagerstätten

The Walcott-Rust Quarry, at Trenton Falls, New York, has yielded a large number of well-preserved, fully articulated fossils from the lower third of the Middle Ordovician Rust Formation, Trenton Group. Along with three species of the more common trilobites from the Trenton Group, fourteen species of rare and uncommon trilobites are found within a thin package of micritic limestones and shales. The first trilobites with preserved appendages,Ceraurus pleurexanthemusGreen, 1832 andFlexicalymene senaria(Conrad, 1842), were described from one layer from this quarry. Unique specimens ofIsotelus walcottiUIrichinWalcott, 1918, andSphaerocorphe robustaWalcott, 1875, were found in the next higher bed. Re-excavation of the quarry yielded information about the taphonomy of the trilobites and stratigraphy of the trilobite layers. Nearly half of the beds surveyed (n = 50) yield direct evidence of obrution (i.e., rapid post-mortem or live burial) of benthic organisms. Unusual anaerobic microenvironments in partially enrolled trilobites of theCerauruslayer facilitated very early calcification of appendages and other soft parts.