TL;DR: 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.
Abstract: 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 pleurexanthemus Green, 1832 and Flexicalymene senaria (Conrad, 1842), were described from one layer from this quarry. Unique specimens of Isotelus walcotti UIrich in Walcott, 1918, and Sphaerocorphe robusta Walcott, 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 the Ceraurus layer facilitated very early calcification of appendages and other soft parts.
TL;DR: Two new genera of cheirurinid trilobites are described from the lower Whittaker Formation (?Rocklandian to Edenian; late Middle and early Late Ordovician) of the southern Mackenzie Mountains as discussed by the authors.
Abstract: Two new genera of cheirurinid trilobites are described from the lower Whittaker Formation (?Rocklandian to Edenian; late Middle and early Late Ordovician) of the southern Mackenzie Mountains. The monotypic genus, Whittakerites n. gen., is a probable descendant of Ceraurus and is presently known only from northern Canada. Borealaspis n. gen. is established for two species from northern Canada, one of which possibly occurs in northern Greenland, and includes B. numitor (Billings) from Anticosti Island. New species described are Whittakerites planatus, Borealaspis whittakerensis, and B. biformis.
TL;DR: A slender extension of a rounded stump on the proximal portion of the left genal spine of Ceraurus plattinensis Foerste, 1920 from the Middle Ordovician of Ontario, Canada records the partial regeneration of a Genal spine.
Abstract: A slender extension of a rounded stump on the proximal portion of the left genal spine of Ceraurus plattinensis Foerste, 1920 from the Middle Ordovician of Ontario, Canada records the partial regeneration of a genal spine. The regenerated spine possesses almost normal prosopon of fine granules and resembles the distal portion of the normal right genal spine. It demonstrates the following aspects about this trilobite's physiology: partial regeneration of genal spines could take place even if severed proximally. partial regeneration of genal spines could take place even in late holaspid individuals and the pattern of regeneration took place in a distoproximal order.