The 555-Million-Year-Old Scratches That Record an Animal's First Meal

In South Australia's Flinders Ranges, a 555-million-year-old seafloor preserved in fine sandstone still bears the impressions of organisms that fed like modern animals — by grazing on microbial mats. These are the trace fossils of the Ediacaran Period, and they record something the body fossils cannot: behaviour.

The Difference Between Body and Trace

Ediacaran body fossils — the familiar fronds, discs, and quilts — tell us what these organisms looked like. But trace fossils tell us what they did. In the Flinders Ranges, paleontologists have found feeding traces associated with the bilaterian Kimberella, a slug-like organism that scraped the microbial mat like a garden rake. The scratch marks are preserved in parallel sets, each set slightly offset from the last, as though the animal moved forward between meals.

These traces are not random. They show directionality, repetition, and purpose. Kimberella did not drift with currents or sit passively on the seafloor. It moved, it fed, and it left evidence of choice.

The oldest known feeding traces are not bones or shells. They are scratches in a microbial lawn, preserved for half a billion years.

A Garden of Scratches

Other trace fossils from the same beds show different behaviours. Horizontal burrows — the oldest known — record worm-like animals pushing through sediment beneath the mat. These are not the deep, complex burrows of the Cambrian, but simple tunnels, a few millimetres wide, that prove some Ediacaran animals could move through, not just across, the seafloor.

In the Nilpena Ediacara National Park, researchers have mapped entire bedding planes covered with overlapping feeding traces. The pattern suggests a community of grazers living at low density, moving slowly across the mat, never exhausting their food supply. It is a snapshot of an ecosystem that worked — stable, efficient, and entirely microbial at its base.

The Limits of the Trace

Ediacaran trace fossils are frustratingly limited. They record only the simplest behaviours: resting, grazing, burrowing. No predation, no complex burrow networks, no signs of territoriality or social structure. The animals that made them had no skeletons, no claws, no jaws. They could push sediment aside or scrape a mat, but they could not dig deep or break through.

Yet that simplicity is itself a datum. The Ediacaran world was not a failed rehearsal for the Cambrian. It was a working ecosystem built on different rules — slow metabolisms, low predation pressure, and a food web that ran on microbial production. The traces record the boundaries of that world.

What the Scratches Tell Us

The oldest feeding traces in the fossil record are not dramatic. They do not record a chase or a kill. They record a small animal scraping a living from a bacterial lawn, one scratch at a time. But they prove that 555 million years ago, animals were already doing what animals do: moving, eating, and leaving a mark.

In the Flinders Ranges, the scratches outlasted the scratchers. The mat is gone, the sea is gone, the continent has drifted. But the traces remain — evidence that behaviour, too, can become a fossil.