Ancient jellyfish suffered strange, sandy death

Shale hints at unusual series of events that led to animal’s fossilization

SANDY JELLY Over 300 million years ago, a peculiar series of events culminated in the preservation of this 12-centimeter-long, sand-filled jellyfish fossil. Its body is at right and tentacles stretch left.

G. Young

By Thomas Sumner

October 28, 2014 at 1:30 pm

VANCOUVER — Tentacle-draped jellyfish might seem odd, and their deaths can be even weirder. Paleontologist Graham Young of the Manitoba Museum in Winnipeg reconstructed the bizarre final moments of an ancient jellyfish entombed for roughly 310 million years inside a black shale slab in Indiana.

The index card–sized jellyfish became stranded on a prehistoric beach, Young thinks. Floundering to free itself, the jellyfish filled up with sand. After dying, a storm or large wave probably carried the sand-filled carcass into a nearby oxygen-deprived lagoon, where it sank into the muddy earth. Over time the ground hardened into black shale, trapping the jellyfish and its sand-filled belly inside.

The jellyfish’s multistep preservation could help explain how unusual sand patches get embedded in geologic formations typically devoid of sand, Young said October 21 at the Geological Society of America’s annual meeting.