Chains of trilobite fossils unearthed in Morocco suggest that these early arthropods were capable of a collective behavior seen in many of today’s species — only these trilobites had the conga line down about 480 million years ago.
Modern vertebrates and invertebrates alike engage in many forms of collective behavior, such as seasonal mass migrations. But paleontologists have been uncertain about when and why such coordinated action began.
Previous studies of Chinese marine fossils that are about 520 million years old suggested the shrimp-like animals, preserved in a line, were exhibiting a collective behavior. Critics, however, have pointed out inconsistencies in the direction the animals were oriented, and the inconclusive conditions of preservation. It’s more likely, they claim, that the early arthropods were deposited in a jumbled line post-mortem.
Into these murky waters march several chains of trilobites from the Fezouata Shale formation near Zagora, Morocco.
