WIKIMEDIA, SANJAY ACHARYAResearchers have found organic molecules sealed inside the fossilized remains of 340-million-year-old fossilized sea creatures called crinoids, according to a study published in the March issue of Geology. The molecules are the oldest to ever be isolated directly from a fossilized organism, and may shed light on evolutionary relationships between ancient and living crinoid species and other echinoderms.

Fragments of biological molecules are often found scattered in rock, said coauthor William Ausich, a geologist at Ohio State University, in a press release. “But this is the oldest example where anyone has found biomarkers inside a particular complete fossil.”

The fossilized crinoids—spindly, plant-like animals with multiple feathery arms, which are used to gather food particles—were buried alive in the Midwest roughly 340 million years ago, when much of North America was under the ocean. Graduate student Christina...