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[dinosaur] Fwd: Dinosaurs in decline tens of millions of years before their final extinction




Apparently this post has been blocked on the DML. I'll try again. Apologies if the original shows up later...


---------- Forwarded message ----------
From: Ben Creisler <bcreisler@gmail.com>
Date: Mon, Apr 18, 2016 at 12:38 PM
Subject: Dinosaurs in decline tens of millions of years before their final extinction
To: dinosaur-l@usc.edu, vrtpaleo-l@usc.edu



Ben Creisler
bcreisler@gmail.com

A new paper:

Manabu Sakamoto, Michael J. Benton, and Chris Venditti (2016)
Dinosaurs in decline tens of millions of years before their final extinction.
Proceedings of the National Academy of Sciences (advance online publication)
doi:10.1073/pnas.1521478113




Significance

Whether dinosaurs were in decline before their final extinction 66 Mya has been debated for decades with no clear resolution. This dispute has not been resolved because of inappropriate data and methods. Here, for the first time to our knowledge, we apply a statistical approach that models changes in speciation and extinction through time. We find overwhelming support for a long-term decline across all dinosaurs and within all three major dinosaur groups. Our results highlight that 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 66 Mya.

Abstract

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.

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