The oldest evidence for brood care in the fossil record comes from a specimen of Waptia fieldensis, an early arthropod relative of shrimp and lobsters. Waptia lived in what is now known as the Burgess Shale fossil deposit in Canada, which is dated to the Cambrian period – around 500 million years ago.
In 2015, five specimens of Waptia were found containing up to 24 eggs each. The eggs were relatively big: an average diameter of 2mm compared to the 8cm of the mother’s body length. This is an example of what scientists call “K-selection strategy of reproduction,” which means that Waptia laid relatively small clutches of eggs for an invertebrate, taking care of them for an extended period of time instead of leaving the offspring to fend for themselves.
Just like most arthropods, this early creature had a segmented body. The first segment, which protected its head, was split into two parts – what is known as a “bivalved carapace.” It was within this carapace, attached to the inner surface, that the animal kept its eggs.