The Dawn of Birds

Fig.1. A green-naped lorikeet, a little owl, an Adélie penguin, and a northern cardinal show only a fraction of the remarkable diversity of birds (Credit: Benjamint, 2009; Trebol-a, 2011; Reinhard Jahn, 2007; & Stephen Wolfe, 2011)

Around 65 million years ago, one of the largest mass extinction events in Earth’s history occurred. An estimated 75 percent of all species went extinct, from non-avian dinosaurs to types of mollusks, plankton, insects, and plants. With extinction, however, came the chance for animals like birds to diversify and expand into empty ecological niches in a process called adaptive radiation. Although the Cretaceous-Paleogene extinction event (K-Pg) may have enabled the rapid evolution of new species of birds, research published last Friday in the journal Science Advances suggests that birds have a much longer and more complicated history than previously thought.

Rulers of the Sea

Fig.1. The T. rex died out 66 million years ago, along with other non-avian dinosaurs, leaving ray-finned fishes to dominate in the waters (Credit: A.E. Anderson, AMNH 5027 [left] and Magnus Manske, 2004 [right])

Even though we were excited to see a Tyrannosaurus rex in “Jurassic World,” it is probably best that they stayed in the Cretaceous. Humans and dinosaurs certainly do not mix, but ancient mammals lived side-by-side with the T. rex. That is, until the asteroid killed off all non-avian dinosaurs in the Cretaceous-Paleogene [K/Pg] extinction event, leaving an ecological void for mammals to evolve and ultimately dominate in terrestrial ecosystems. A recent study published in PNAS by paleobiologists at UC San Diego suggests a similar story unfolded with the evolution of fish in the oceans.