Enameloid-bound δ N reveals large trophic separation among Late Cretaceous sharks in the northern Gulf of Mexico.

The nitrogen isotopic composition ( N/ N ratio, or δ N) of enameloid-bound organic matter (δ N ) in shark teeth was recently developed to investigate the biogeochemistry and trophic structures (i.e., food webs) of the ancient ocean.

Lipid biomarkers recording marine microbial community structure changes through the Frasnian-Famennian mass extinction event.

Studying the response and recovery of marine microbial communities during mass extinction events provides an evolutionary window through which to understand the adaptation and resilience of the marine ecosystem in the face of significant environmental disturbances. The goal of this study is to reconstruct changes in the marine microbial community structure through the Late Devonian Frasnian-Famennian (F-F) transition. We performed a multiproxy investigation on a drill core of the Upper Devonian New Albany Shale from the Illinois Basin (western Kentucky, USA).

Two-step extinction of Late Cretaceous marine vertebrates in northern Gulf of Mexico prolonged biodiversity loss prior to the Chicxulub impact.

Recent studies on mass extinctions are often based on the global fossil record, but data from selected paleogeographic regions under a relatively constant paleoenvironmental setting can also provide important information. Eighty-nine marine vertebrate species, including cartilaginous and bony fish and marine reptiles, from northern Gulf of Mexico - located about 500 km from the Chicxulub crater - offer a unique opportunity to determine an extinction process during the last 20 million years of the Late Cretaceous. Our diversity data show two separate extinction events: (i) the 'Middle Campanian Crisis' (about 77 Mya) and (ii) the end-Maastrichtian (66 Mya) events.

Geochemical Evidence of First Forestation in the Southernmost Euramerica from Upper Devonian (Famennian) Black Shales.

The global dispersal of forests and soils has been proposed as a cause for the Late Devonian mass extinctions of marine organisms, but detailed spatiotemporal records of forests and soils at that time remain lacking. We present data from microscopic and geochemical analyses of the Upper Devonian Chattanooga Shale (Famennian Stage). Plant residues (microfossils, vitrinite and inertinite) and biomarkers derived from terrestrial plants and wildfire occur throughout the stratigraphic section, suggesting widespread forest in the southern Appalachian Basin, a region with no macro plant fossil record during the Famennian.

Histology-based morphology of the neurocentral synchondrosis in Alligator mississippiensis (Archosauria, Crocodylia).

Morphology of the neurocentral synchondroses--thin cartilaginous layers between centra and neural arches--are documented in the extant crocodilian, Alligator mississippiensis (Archosauria, Crocodylia). Examination of dry skeletons demonstrates that neurocentral suture closure occurs in very late postnatal ontogeny (after reaching sexual maturity and/or body size ca. 40% from the upper range).

A nomenclature for vertebral fossae in sauropods and other saurischian dinosaurs.

Background: The axial skeleton of extinct saurischian dinosaurs (i.e., theropods, sauropodomorphs), like living birds, was pneumatized by epithelial outpocketings of the respiratory system.