Publication Date


Series Number



Beecher's Trilobite Bed in the Frankfort Shale of New York State preserves an exceptional record of the benthic macrofauna of a Late Ordovician deepwater marine environment. It has long been famous for specimens of the trilobites Triarthrus eatoni (Hall), Cryptolithus bellulus (Ulrich), Primaspis crosotus (Locke), and Cornuproetus beecheri (Ruedemann), new combination, which preserve the ventral appendages and even traces of the musculature. This fossil assemblage was accumulated when benthic animals and associated detritus were caught up and buried by a turbidity flow. Burial was indirectly the cause of mortality; and this factor, together with the abundance of already decayed organic matter in the sediment, the protection of a thickness of fine sediment, and sedimentary compaction following soon after burial, contributed to the exceptionally fine preservation of these animals in iron pyrite. As a natural census, this assemblage reveals the "preservable" benthic macrofauna as comprised of some 24 species of epifaunal and shallow infaunal organisms, chief among which were deposit-feeding trilobites (2 common species comprising 58 percent of individuals), suspension-feeding dendroid graptolites (3 species; 22 percent) and brachiopods (3 species; 9 percent). Annelids were probably abundant; large, poorly preserved specimens comprise about 6 percent of the sample. As compared with the benthic faunas of similar modern environments in deep basins on the continental borderland off southern California, this Ordovician fauna differs greatly in high-level taxonomic composition but has very much the same level of diversity in "preservable" species.