Ecological niche modelling does not support climatically-driven dinosaur diversity decline before the Cretaceous/Paleogene mass extinction

Abstract

In the lead-up to the Cretaceous/Paleogene mass extinction, dinosaur diversity is argued to have been either in long-term decline, or thriving until their sudden demise. The latest Cretaceous (Campanian–Maastrichtian [83–66 Ma]) of North America provides the best record to address this debate, but even here diversity reconstructions are biased by uneven sampling. Here we combine fossil occurrences with climatic and environmental modelling to quantify latest Cretaceous North American dinosaur habitat. Ecological niche modelling shows a Campanian-to-Maastrichtian habitability decrease in areas with present-day rock-outcrop. However, a continent-wide projection demonstrates habitat stability, or even a Campanian-to-Maastrichtian increase, that is not preserved. This reduction of the spatial sampling window resulted from formation of the proto-Rocky Mountains and sea-level regression. We suggest that Maastrichtian North American dinosaur diversity is therefore likely to be underestimated, with the apparent decline a product of sampling bias, and not due to a climatically-driven decrease in habitability as previously hypothesised.

Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction

“…This implies a very rapid recovery of marine productivity (45,46), which argues against the suggested delay in ecosystem reset caused by continued Deccan volcanism after the K/Pg boundary (9,45,46). In contrast to the end-Permian mass extinction, the K/Pg event was geologically instantaneous (2-4, 10, 23, 35), and there is no clear evidence for a prolonged decline (3,4,35,47) that would be required for Deccan volcanism to trigger a mass extinction-level event due to the short residence time of stratospheric aerosols. In addition, studies on marine macrofossils from Antarctica are consistent with a sudden, catastrophic driver for the extinction, such as the bolide impact, rather than a significant contribution from Deccan Traps volcanism during the latest Cretaceous (48).…”

Dinosaurs Still in Long-Term Net Speciation Decline Before the K-Pg Boundary

“…While the ENM implemented by Chiarenza et al 1 is impressive and we have no reason to question the accuracy of their model, linking the projected suitable habitat with species diversity presents a slight problem. That is, even though a particular region of geography may represent a suitable habitat for a particular clade, that does not prove that it was inhabited by the target species for any number of reasons -e.g., geographical barriers, low dispersal rates, etc.…”

“…More crucially, diversity (= species richness) as implied by Chiarenza et al 1 from their ENM, equates to the numbers of taxa within distinct intervals of time -e.g., geological stages. This is regardless of whether various sources of bias have been accounted for -e.g., through the use of rarefaction, SQS 3 , TRiPS 4 , or spatial sampling standardization 5 .…”

Climatic shifts drove major contractions in avian latitudinal distributions throughout the Cenozoic

“…The avian fossil record reveals information on where early representatives of various lineages were found and, just as importantly, when in Earth history these birds lived. Paleontological evidence for major fluctuations in avian historical biogeographic patterns therefore raises questions about the extent to which historical factors, such as Cenozoic climatic change, may have been responsible for driving historical shifts in avian geographic range, as has been demonstrated for ectothermic clades, such as turtles (40), and dismissed as a factor influencing the demise of nonavian dinosaurs in the Late Cretaceous (41). Here, we integrate both past and present avian distributional data and climate characterizations to model how habitable regions for 10 neornithine higher level clades ( Fig.…”