Examples of skeletal deformities abound in the animal kingdom—think malformed limbs or an abnormal number of toes. Now, researchers have reported the oldest record of a vertebral malformation in an aquatic animal, a deformity that likely led to scoliosis in the 80-centimeter-long marine reptile known as Stereosternum tumidium. The fossils (shown above), unearthed in Brazil and roughly 300 million years old, reveal an 18th vertebra that failed to develop properly, a condition that curved this animal’s spine and likely limited its flexibility, the researchers report this week in PLOS ONE. However, this S. tumidium was an adult when it died, the team concluded based on the size of the nearly complete fossilized skeleton. That means its scoliosis wasn't too detrimental to its ability to hunt its favorite food—crustaceans—or evade predators. Perhaps S. tumidium swam relatively slowly and relied largely on its tail to propel itself, the scientists suggest.