Paleontologists are besotted, but the objects of their affection have hearts of stone. In a first, scientists have discovered whole, perfectly preserved fossil hearts, found in fish unearthed in Brazil. The exceptional organs offer solid clues in our understanding of heart evolution.

A 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. 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.

Armed with noninvasive CT scanners, the team created highly detailed models of the two