Everyone knows about the mass extinction that ended the age of dinosaurs. This is often said to have opened the way for the age of mammals and eventually us.
Of course, it wasn’t exactly like that.
In the wake of the mass extinction, there was an explosive radiation of all the surviving species, not just mammals.
This month saw two articles about this exciting period.
First of all, the dinosaurs didn’t actually all die out. One whole wing of the family survived and thrived until today: the birds.
Ksepka, Daniel T., Thomas A. Stidham, and Thomas E. Williamson report on new findings which document the rapid diversification of birds after the extinction event.. Specifically, they report a small bird that is dated from the very early Paleocene, i.e., soon after the end of the dinosaurs. They argue that dating this species implies that four major groups of birds arose soon after that.
The authors comment that this observation puts the diversification of birds on approximately the same time line as the expansion of mammals.
In a different study, Yan-Jie Feng and collagues analyzed DNA from 156 living species of frogs to construct a putative taxonimic history, anchored by 20 representative fossils . The results suggest that “three species-rich clades (Hyloidea, Microhylidae, and Natatanura), which together comprise ∼88% of extant anuran species, simultaneously underwent rapid diversification” right after the end of the dinosaurs. (, p. 1)
They argue that the “mass extinction may have triggered explosive radiations of frogs by creating new ecological opportunities.” There is a very telling diagram in the full article, with a gigantic fan out of species just past the red line of the Cretaceous extinction event.
The researchers comment that their molecular study is important because the fossil record of frogs is sparse. This is one of the clearest pictures, albeit indirectly, that documents the evolutionary history of frogs during this period.
Again, this is the same time scale as mammals and birds, suggesting that there was a mad evolutionary scramble to fill the huge void left by the mass extinction at the end of the Cretaceous.
After the Dinosaurs came not the “Age of Mammals” but the “Age of Pretty Much Everything Except Non-Avian Dinosaurs”! 🙂
- Yan-Jie Feng, David C. Blackburn, Dan Liang, David M. Hillis, David B. Wake, David C. Cannatella, and Peng Zhang, Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences, July 3, 2017 2017. http://www.pnas.org/content/early/2017/06/26/1704632114.abstract
- Daniel T. Ksepka, Thomas A. Stidham, and Thomas E. Williamson, Early Paleocene landbird supports rapid phylogenetic and morphological diversification of crown birds after the K–Pg mass extinction. Proceedings of the National Academy of Sciences, July 10, 2017 2017. http://www.pnas.org/content/early/2017/07/05/1700188114.abstract