Rare fossil found in world War I trench.

• Position: Earth Science

An unusual fossil find is giving scientists new ideas about how some of the earliest animals on Earth came to dominate the world's oceans. An international research team found 425,000,000-year-old fossilized remnants of juvenile crinoids, a distant ancestor of today's sea lilies, encased in iron oxide and limestone in the Austrian Alps.

Researchers collected the rock from a formation on the border between Italy and Austria known as the Cardiola Formation, which was exposed in trenches dug during World War I.

Crinoids were abundant long ago, when they carpeted the sea floor. Most stalked crinoid fossils depict spindly, plantlike animals anchored to sea floor rocks, explains earth scientist William Ausich, coauthor of a study in Geologica Acta.

Fossils of juvenile crinoids are rare, he explains. Rarer still is that these newly uncovered crinoids were not attached to rocks when they died. Whatever they were attached to during their young lives did not survive fossilization.

'The fossils indicate that they were either attached to objects floating in the water at the time, or attached to another bottom dweller that lacked preservable hard parts." They might have clung to freefloating algae beds or swimming cephalopods, either of which could have carried them far away from where they formed as larvae.

Sea lilies reproduce by ejecting sperm and eggs into the water. Larvae grow into free-floating juvenile animals and eventually attach to the ocean bottom, where they grow to adulthood within 18 months--at least that is what sea lilies do today. This fossil find suggests that their distant ancestors sometimes settled on objects that carried them far from...