Dinosaur morphological diversity and the end-Cretaceous extinction

Area of Science:

• Paleontology
• Evolutionary Biology
• Stratigraphy

Background:

• The extinction of non-avian dinosaurs 65 million years ago is a significant event in Earth's history.
• Ongoing debate exists regarding whether dinosaur biodiversity declined prior to the end-Cretaceous extinction event, which was potentially caused by volcanism and bolide impact.
• Understanding pre-extinction trends is crucial for reconstructing dinosaurian ecological dynamics.

Purpose of the Study:

• To quantify the morphological disparity (anatomical variability) of seven major dinosaur subgroups during the latest Cretaceous period.
• To assess global and regional patterns of dinosaurian morphological disparity.
• To determine if a universal biodiversity decline preceded the Cretaceous–Paleogene extinction.

Main Methods:

• Calculation of morphological disparity using anatomical data from seven major dinosaur subgroups.
• Analysis of disparity trends at both global and regional scales across the latest Cretaceous.
• Comparison of disparity trends among different clades and geographic locations.

Main Results:

• Significant geographic and clade-specific heterogeneity in morphological disparity was observed.
• Large-bodied, bulk-feeding herbivores (ceratopsids and hadrosauroids) and some North American taxa showed declining disparity in the final two Cretaceous stages.
• Carnivorous dinosaurs, mid-sized herbivores, and some Asian taxa did not exhibit such declines.

Conclusions:

• Late Cretaceous dinosaurian evolution was complex, with no uniform biodiversity trend across all groups.
• The North American fossil record may represent localized patterns rather than global trends.
• Certain dinosaur groups experienced long-term declines in morphological variability preceding their extinction.