Dinosaurs and the Cretaceous Terrestrial Revolution

Area of Science:

• Paleontology
• Evolutionary Biology
• Phylogenetics

Background:

• Dinosaur diversity peaked in the Late Cretaceous, a period of significant evolutionary change known as the Cretaceous Terrestrial Revolution (KTR).
• It remains debated whether dinosaurs participated in the KTR, which saw rapid expansion in flowering plants, insects, squamates, birds, and mammals.

Purpose of the Study:

• To quantitatively assess dinosaur diversification patterns using a new supertree.
• To determine if the apparent Late Cretaceous dinosaur diversity burst is a true evolutionary event or a result of sampling bias.
• To investigate the relationship between dinosaur evolution and the KTR.

Main Methods:

• Construction of a new supertree integrating diverse dinosaur fossil data.
• Quantitative analysis of diversification rates across the dinosaur evolutionary timeline.
• Statistical testing against null models of lineage branching, such as the equal rates model.

Main Results:

• The apparent explosion of dinosaur diversity in the Late Cretaceous is identified as a sampling artifact.
• Major dinosaur diversification shifts primarily occurred in the first third of their evolutionary history.
• No significant diversification shifts correlate with the emergence of new dinosaur clades in the later Cretaceous.

Conclusions:

• Dinosaur evolution was not directly driven by the KTR.
• Dinosaurs did not experience a progressive decline in diversity before their extinction.
• The observed Cretaceous dinosaur diversity pattern is consistent with an equal rates model of lineage branching, suggesting earlier diversification events were more significant.