A possible scene from 500 million years ago:
The ocean floor crawls with roving packs of arthropods called trilobites. Instead of sticking to its normal diet of plankton or algae, one hungry trilobite looks around at its trilobite friends and sees dinner. Welcome to cannibalism in the deep.
Mark McMenamin, a paleontologist from Mount Holyoke College, recently announced that fossil records show trilobites attacking smaller trilobites. Researchers previously knew that the animals could be predatory, but no one had suggested that they ate each other.
McMenamin studied trilobites preserved in slabs of rock and noticed that some of the fossils showed evidence of violence. There were trilobites climbing on top of each other, trilobites with bite marks and even a trilobite ripping another one in half.
“There may be a dark side of these little creatures,” McMenaman told Discovery News.
McMenaman will formally present his findings in November at a meeting of the Geological Society of America. Some scientists are already skeptical of his claims. They believe the attacks could be a sign of mating. Other arthropods, like crabs, are known for violent behavior during sexual reproduction.
Trilobites have fascinated geologists for years. The critters appear in the fossil record during an era called the Cambrian Explosion – a sudden burst in biological diversity about 540 million years ago. Though trilobites died off about 300 million years ago, similar anatomic structures can be seen in insects and crustaceans today.
– Madeline McCurry-Schmidt