Scientists Say Even Earliest Trilobites Could Roll Themselves Up Like Pillbugs
Posted on October 11, 2013
Trilobites are an ancient marine creature that thrived for over 270 million years. The survived even as the numbers of predators they faced increased. Scientists have known that trilobites could roll up their bodies like a pillbug (pill woodlouse), but until now it was generally not believed that the earliest forms of trilobites could use this defensive technique. A new fossil find indicates the early trilobites (called olenellids) could also roll themselves up. This presented potential predators with a heavily armored shield that was difficult for them to attack. The olenellids may have been the very first enrolling animal.
During field research in Jasper National park in Alberta, Canada, Javier Ortega-Hernandez and his PhD supervisor Nicholas Butterfield found two specimens that were tiny but highly significant.
Ortega-Hernandez said in a release, "The first specimen is unusual for an olenellid, as the tail covers the underside of the head completely - a typical characteristic of enrolment. The second shows overlapping segments in the body. Taken together, these are an exciting find, as it is clear evidence that, despite their limitations, olenellids were capable of rolling themselves up effectively."
The olenellid's rolling up defense was not as developed as the trilobite species that came after them. The scientists say the later trilobites developed extra defenses, such as locking devices in their heads and tails. This meant predators could not pull the trilobites back open after they had rolled up into a ball.
Ortega-Hernandez adds, "It's long been known that trilobites became very efficient at avoiding predators, and the fact that they fossilized easily means that there is rich and abundant record of them in both their outstretched and enrolled states. But no-one had ever seen an enrolled fossil of this very early trilobite group known as olenellids, so it was assumed that they did not have enrolling ability at this stage of evolution."