Evidence from ammonoids and conodonts for multiple Early Triassic mass extinctions

Evidence from ammonoids and conodonts for multiple Early Triassic mass extinctions.

Ammonoids and conodonts, being characterized by exceptionally high background rates of origination and extinction, were vulnerable to global environmental crises, which characteristically intensified background rates of extinction. Thus, it is not surprising that these taxa suffered conspicuous mass extinctions at the times of three negative Early Triassic global carbon isotopic excursions that...

Morphological disparity of ammonoids and the mark of Permian mass extinctions.

The taxonomic diversity of ammonoids, in terms of the number of taxa preserved, provides an incomplete picture of the extinction pattern during the Permian because of a strongly biased fossil record. The analysis of morphological disparity (the variety of shell shapes) is a powerful complementary tool for testing hypotheses about the selectivity of extinction and permits the recognition of thre...

Geologically rapid Late Triassic extinctions: Palynological evidence from the Newark Supergroup

Orbitally controlled, sedimentary cycles of the Newark Supergroup permit palyniferous Late Triassic sections to be calibrated in time. Carnian palynofloras from · the Richmond basin exhibit 2-m.y. fluctuations in the spore/pollen ratio, but taxonomic composition remains stable. Diversity of Norian and Rhaetian palynofloras increases prior to a 60% reduction at the Triassic/Jurassic boundary. Th...

Conodonts from the Early Triassic microbialite of Guangxi (South China): implications for the definition of the base of the Triassic System

Evolutionary patterns from mass originations and mass extinctions.

The Fossil Record 2 database gives a stratigraphic range of most known animal and plant families. We have used it to plot the number of families extant through time and argue for an exponential fit, rather than a logistic one, on the basis of power spectra of the residuals from the exponential. The times of origins and extinctions, when plotted for all families of marine and terrestrial organis...