The new scans, published in eLife on Tuesday, hint that bony fish went through some intriguing changes in the ways they regulate blood flow through the heart. “We’re studying the tips of a tree … we’re not looking at the branches.” Protective Pulse “It’s interesting, since we’ve had to draw inferences from organisms,” says James Hicks of the University of California, Irvine, an expert on vertebrate heart evolution who wasn’t involved with the study. But until now, researchers haven’t had the benefit of fossils to know for certain what ancient hearts looked like, since soft tissues such as hearts degrade easily and are notoriously finicky to preserve. To uncover the heart’s evolutionary history, scientists have long examined its anatomy across species and have constructed elaborate family trees based on genetics. But amphibians get by with just three chambers, and in today’s fish, the heart has an atrium and a single pumping ventricle. Modern mammals have four-chambered hearts featuring a left and right atrium and a left and right ventricle. Today, the heart is a stunningly diverse, complex organ with different architectures across the animal kingdom. The two specimens, which are between 113 and 119 million years old, hail from the Santana formation, a Cretaceous site in northeast Brazil renowned for its exceptionally preserved fossils.Īrmed with noninvasive CT scanners, the team created highly detailed models of the two fish, which hint at how fish hearts have changed over time. The exceptional organs offer solid clues in our understanding of heart evolution.Ī team of researchers led by Lara Maldanis and Murilo Carvalho of the Brazilian Biosciences National Laboratory found the hearts in previously collected fossils of Rhacolepis buccalis, a now extinct species of bony fish. In a first, scientists have discovered whole, perfectly preserved fossil hearts, found in fish unearthed in Brazil. Paleontologists are besotted, but the objects of their affection have hearts of stone.
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