Dinosaurs in decline tens of millions of years before their final extinction.
Whether dinosaurs were in a long-term decline or whether they were reigning strong right up to their final disappearance at the Cretaceous-Paleogene (K-Pg) mass extinction event 66 Mya has been debated for decades with no clear resolution. The dispute has continued unresolved because of a lack of statistical rigor and appropriate evolutionary framework. Here, for the first time to our knowledge, we apply a Bayesian phylogenetic approach to model the evolutionary dynamics of speciation and extinction through time in Mesozoic dinosaurs, properly taking account of previously ignored statistical violations. We find overwhelming support for a long-term decline across all dinosaurs and within all three dinosaurian subclades (Ornithischia, Sauropodomorpha, and Theropoda), where speciation rate slowed down through time and was ultimately exceeded by extinction rate tens of millions of years before the K-Pg boundary. The only exceptions to this general pattern are the morphologically specialized herbivores, the Hadrosauriformes and Ceratopsidae, which show rapid species proliferations throughout the Late Cretaceous instead. Our results highlight that, despite some heterogeneity in speciation dynamics, dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event.
School of Biological Sciences, University of Reading, Reading RG6 6BX, United Kingdom; m.sakamoto@reading.ac.uk c.d.venditti@reading.ac.uk.
Manabu
M
Sakamoto
School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom.
Michael J
MJ
Benton
School of Biological Sciences, University of Reading, Reading RG6 6BX, United Kingdom; m.sakamoto@reading.ac.uk c.d.venditti@reading.ac.uk.
Chris
C
Venditti
D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D025061:Dinosaurs / Q000145:classification* / Q000254:growth & development*; D017753:Ecosystem; D053476:Extinction, Biological; D015233:Models, Statistical; D011157:Population Dynamics; D013045:Species Specificity
Bayesian methods; dinosaurs; evolution; phylogeny; speciation