Steve Brusatte – The Rise and Fall of the Dinosaurs: A New History of a Lost World
A history of the dinosaurs organized chronologically rather than by theme, and in my opinion, better than Brian Switek’s still-quite-good My Beloved Bronosaurus. Brusatte shares Switek’s mostly endearing fanboy enthusiasm for his subject, and recounts a few stories of meeting and even working with some of his idols.
Brusatte traces dinosaurs’ origins back to the Permian extinction, and more clearly differentiates the Triassic, Jurassic, and Cretaceous periods. One thing that comes out of chronological approach is that evolution doesn’t have a clear direction. Things change, but not necessarily for better or worse over time.
The Jurassic’s apex predator was the Allosaurus, and the Cretaceous’ was the Tyrannosaurus Rex. They had their differences, and Brusatte does an excellent job describing them, and tracing back their family tree—they are more cousins than a direct lineage. T-Rex’s direct ancestor was likely a mid-Jurassic dinosaur that weighed about 100 pounds, and grew into its niche after the Jurassic-Cretaceous boundary created an opening for a large apex predator.
Another fun insight has to do with dinosaur breathing. The large sauropods such as the diplodocus, brachiosaurs, and Argentine titanosaurs could exceed 100 feet in length and required an enormous amount of energy. Not just to maintain their bulk, but to grow it. It likely took just 30 or 40 years for a sauropod to reach full size. By contrast, humans can take nearly 20 years to grow from a similar starting point to perhaps 6 feet. This required eating about 100 pounds of food every day, which required a massive, and efficient respiratory system to provide enough oxygen to burn all that fuel and power the digestive system—all while constantly providing enough oxygen for cells from head-to-tail.
Rather than lungs such as we and smaller dinosaurs share, sauropods evolved a different kind of lung found in today’s birds. We breathe in oxygen and exhale carbon dioxide. Sauropod and bird lungs extract oxygen on the inhale as well, but extract a second round of oxygen on the exhale as well, making them more efficient. This allowed sauropods to meet their needs. This design is also lightweight, which is why birds use it—it’s easier to fly with less cargo.
Sauropod bones were also relatively less dense. While not hollow, they did feature hollow chambers and air pockets inside—not quite like a honeycomb structure seen in high-tech aircraft material designs, but serving the same purpose of preserving strength while minimizing weight. If giant lumbering sauropod dinosaurs had not evolved adaptations to their niche in both respiration and bone structure, today’s graceful hummingbirds may never have evolved as we know them.