Ottawa - Long before kangaroos carried their joeys in their pouches and honey bees nurtured their young in hives, there was the 508-million-year-old Waptia.

Little is known about the shrimp-like creature first discovered in the renowned Canadian Burgess Shale fossil deposit a century ago. But a recent study has found eggs with embryos preserved within the body of the animal, suggesting that his is the oldest example of brood care in the fossil record.

This shrimp-like creature lived in the ocean 508 million years ago and toted eggs under its shell, making this the oldest evidence of a living thing that carried its offspring. 'The discovery adds another piece to our understanding of brood care practices during the Cambrian Explosion,' said Jean-Bernard Caron, a curator at the Royal Ontario Museum. 

'This is a period of rapid evolutionary development when most major animal groups appear in the fossil record. Scientists from the University of Toronto, Royal Ontario Museum, and Centre national de la recherche scientifique collaborated in this discovery. Waptia fieldensis is an early arthropod, belonging to a group of animals that includes lobsters and crayfish. It had a two-part structure covering the front segment of its body near the head, known as a bivalved carapace.

Scientists believe the carapace played a fundamental role in how the creature practiced brood care or caring for their young.

'Clusters of egg-shaped objects are evident in five of the many specimens we observed, all located on the underside of the carapace and alongside the anterior third of the body,' said Caron. As the eggs laid inside their mother, the clusters were arranged in a single layer on each side of the body, which makes it almost impossible for the eggs to squish one another.

In some animals, like seahorses, the eggs are resting equidistant from each other, while in others, some are closer together. The largest amount of eggs held by each Waptia was up to 24, 12 on each side of the body.

The scientists analyzed the egg-like structures and found that minerals were different in certain areas of the eggs, which indicates the embryos inside had a different composition.

'This creature is expanding our perspective on the diversification of brood care in early arthropods,' said Jean Vannier, the co-author of the study from Centre national de la recherche scientifique.

'The relatively large size of the eggs and the small number of them, contrasts with the high number of small eggs found previously in another bivalved arthropod known as Kunmingella douvillei. 'And though that creature predates Waptia by about seven million years, none of its eggs contained embryos.'