As for most geological period boundaries, the Triassic–Jurassic (T–J) transition, ∼200 million years ago, was a critical juncture in Earth history during which profound biotic and environmental changes took place. Early comparisons with the end-Cretaceous extinction and the involvement of extraterrestrial impact have now largely, although not entirely, given way to more Earthbound explanations ...

Understanding the origin and diversification of organisms requires a good phylogenetic estimate of their age and diversification rates. This estimate can be difficult to obtain when samples are limited and fossil records are disputed, as in Dictyoptera. To choose among competing hypotheses of origin for dictyopteran suborders, we root a phylogenetic analysis (~800 taxa, 10 kbp) within a large s...

The end-Permian mass extinction is now robustly dated at 252.6 ± 0.2 Ma (U–Pb) and the Permian–Triassic (P–T) GSSP level is dated by interpolation at 252.5 Ma. An isotopic geochronological timescale for the Late Permian–Early Triassic, based on recent accurate high-precision U–Pb single zircon dating of volcanic ashes, together with calibrated conodont zonation schemes, is presented. The durati...

Palynological data from the Newark basin of the Newark Supergroup reveal a spike in the spore/pollen ratio at the TriasGc/Jurassic boundary. This spore spike is coincident with a 60% regional extinction of the palynoflora and approximately synchronous with terrestrial vertebrate extinctions. Orbitally controlled sedimentary cycles allow stratigraphic sections to be calibrated in time, constrain...

S WITH PROGRAM TRIASSIC-JURASSIC NON-MARINE BOUNDARY EVENTS IN THE NEWARK, AND HARTFORD BASINS (NEW JERSEY, PENNSYLVANIA, CONNECTICUT, AND MASSACHUSETTS), EASTERN UNITED STATES 2 Field Workshop June 7-12, 2002 Christopher A. McRoberts Department of Geology, State University of New York at Cortland Paul E. Olsen Lamont Doherty Earth Observatory of Columbia University

BACKGROUND Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Tri...