Why did the non-avian dinosaurs become extinct? There’s no shortage of ideas, but no one really knows. And even though paleontologists have narrowed them down to a short list of extinction triggers—including an asteroid strike, massive volcanic outpouring, sea level changes and climate alterations—how these events translated into the extinction of entire clades of organisms remains hotly debated.

Small coelurosaurs like this Troodon appear to have maintained stable levels of disparity during the last 12 million years of the Cretaceous. Image courtesy AMNH/J. Brougham.

Reference

Brusatte, S., Butler, R., Prieto-Márquez, A., & Norell, M. (2012). Dinosaur morphological diversity and the end-Cretaceous extinction Nature Communications, 3 DOI: 10.1038/ncomms1815

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Stephanie Pappas, LiveScience Senior Writer

The earliest creatures to crawl out of the water onto land may have concocted antacids out of their own bones, a clever innovation that would’ve let the animals breathe, researchers now find.

The earliest tetrapods, or four-limbed creatures, made their first evolutionary forays onto land about 370 million years ago. Breathing air came with challenges, though. A major one was getting rid of the air’s carbon dioxide, which, when it builds up, reacts with water in the body and forms an acid.

Now, growing evidence in modern reptiles suggests that bones that grew within the skin of early tetrapods may have acted as a natural antacid by releasing their neutralizing chemicals into the bloodstream. The result would have bought the creatures time to spend on land before they had to head back to the water to rid themselves of excess carbon dioxide.

The skeleton of Eryops, one of the earliest land-walking tetrapods. CREDIT: © Christine M. Janis