201 — Anamorphic development and extended parental care in a 520 million-year-old stem-group euarthropod from China

Post-natal parental care isn’t old news. But today’s paper illustrates how old it parental care of newborns really is: 520 million years old, if this interpretation is correct.

Fuxianhuia protensa was an early-Cambrian euarthropod (a “true arthropod”). Fossils found in Chengjiang, China, show exceptionally well-preserved F. protensae in a group. Among the individuals are four juveniles and one adult. We know the juveniles are the same age (“ontogenetically coeval”, if you want to be fancy) because they are the same size, and we know already that these arthropods grow segments in correlation with their age.

What’s more interesting to many researchers is the presence of the colocated sexually mature individual. Two hypotheses spring to mind: Perhaps the babies are lunch? Or… perhaps this is a parent?

The researchers determined that the fossilized scene likely represents a “life assemblage” because the specimens are so well-preserved. In other words, it’s not serendipity that these animals are found so close together. They were most likely near each other when they all died simultaneously from some external event.

The paper doesn’t explain how we know that this is a parent rather than a predator, but it seems likely based upon the fact that these arthropods are of the same species (parental care is common in certain types of modern-day arthropods as well) and the adult does not seem to be consuming any of the juveniles already.

If this paper is correct, then this 520 million year old parent — probably mother — is the earliest-known instance of parental care on Earth.