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Group behavior occurred already among the first animals as it helped them to survive environmental stress

Fossilized Ampyx priscus in a linear formation, found at the Moroccan Lower Ordovician Fezouata Shale.

An international team of researchers analyzed fossils of trilobites which lived about 480 million years ago

Though our understanding of the anatomy of the earliest animals is growing ever more precise, we know next to nothing about their behavior. One question of special interest is: Did group behavior arise recently or is it primeval? To answer this question, researchers from the French Centre national de la recherche scientifique (CNRS), the Cadi Ayyad University (Marrakech, Morocco), and the University of Lausanne (Switzerland) studied fossilized Moroccan Ampyx priscus trilobites, which lived 480 million years ago. Their closest relatives of today are insects and lobsters.
They showed that the trilobites had probably been buried in their positions – all oriented in the same direction, in orderly lines, maintaining close contact with each other through their long spines. Perhaps they were migrating on the ocean floor as a group or gathered for mating.

By comparing this observation with the behavior of living animals such as North American spiny lobsters, the scientists deduced that these Ampyx processions may illustrate a similar kind of collective behavior – adopted in response to cyclic environmental disturbances like storms or chemical signals associated with reproduction.

This example would seem to suggest that group behavior is of ancient origin and, from an early date, likely conferred an evolutionary advantage on the first animals, allowing them to survive environmental stress and improve their reproductive chances. The findings were published in Scientific Reports.

Trilobites lived in the early oceans of the Paleozoic until the extinction event around 251 million years in the Permian. The exoskeletons of many species are conserved as fossils that help to reconstruct early life on the planet.

Scientific Reports

Video: Spiny Lobster Migration (32:30)

Source: CNRS

(22.10.2019, USA: 10.22.2019)