Oct. 17 (UPI) -- Millions of years before "Conga," Gloria Estefan's hit single from the album Primitive Love, primitive arthropods were doing the dance on the bottom of the ocean floor.
In a new study, published Thursday in the journal Science Advances, researchers in France described the discovery and analysis of several lines of trilobite fossils preserved in 480-million-year old shale deposits.
Scientists have previously found lines of trilobites, but paleontologists theorized the primitive animals were swept into organized lines by currents after they had already perished. Some researchers surmised the animals sometimes became trapped in burrows and perished simultaneously.
But the latest analysis suggests those theories don't make sense. An analysis of several trilobite conga lines in Moroccan deposits showed the animals were all the same age, mature adults, and facing the same direction.
Had currents washed deceased trilobites into a neatly organized grave, one would expect to find a wider variety of ages and at least a few fossils facing backwards. Likewise, there's no evidence the animals became suddenly trapped and buried.
"In contrast, they are made up of articulated mono specific individuals and are not associated with sedimentary structures indicative of sea bottom troughs or burrows," researchers wrote.
Trilobites, Ampyx priscus, were blind, but they had antennas and could sense their environs, as well as one another.
Scientists suspect the trilobites assembled and walked in a line to migrate to distant locations, perhaps to mate or simply to find friendlier environs. In the Caribbean, spiny lobsters file into conga lines every autumn and march their way to deeper, warmer water.
"It shows that collective behavior is not a new evolutionary innovation that appeared a couple of million years ago," lead study author Jean Vannier, a paleontologist at the University of Lyon, told National Geographic. "Instead, it is much older, dating back to the first biodiversification events of animal life."