The Secret History of Sharks: The Rise of the Ocean’s Most Fearsome Predators

In this stimulating study, Long (Prehistoric Australasia), a paleontology professor at Flinders University in Australia, explores “how over the course of 465 million years [sharks] were shaped and honed by a constantly changing world.” Emphasizing the predators’ resilience, Long explains that sharks survived the “Great Dying,” an era of “prolonged volcanic eruptions” 252 million years ago that wiped out around 87% of all marine species, by moving into deeper parts of the ocean that were less affected by the dramatic rise in water temperatures. Sharks have also shown a great capacity for adaptation, Long writes, suggesting their “superpower” is “the ability to craft and shape new tooth types with new tissues” (some species “developed flat crushing or grinding tooth plates” for cracking clams while other grew cladodont teeth, each of which has “three or more prominent pointed cusps”). The comprehensive overview of sharks’ evolutionary history highlights some of the stranger specimens to have prowled the oceans (one ancient species had “large wing-like pectoral fins emerging from near its neck like dystopian underwater butterflies”). Long also sheds light on how paleontologists draw conclusions from a limited fossil record, describing how “analyzing the isotopes of certain elements like nitrogen, carbon, and oxygen” in shark teeth reveals what kinds of prey the carnivores ate. Readers will want to sink their teeth into this. Photos. Agent: Jane von Mehren, Aevitas Creative Management. (July)