Fossils Show How Trilobites Attacked Their Prey

Posted on February 17, 2016

Graphic show show Trilobites captured prey

Scientists have discovered 500-million-year-old fossils in southeastern Missouri that unlock clues to the predatory behaviors of trilobites. Trilobites are an extinct invertebrate animal with an external skeleton. They flourished during the Cambrian period.

Geologists and paleobiologists at the University of Missouri (MU) collaborated to study fossils that reveal the predatory behaviors of trilobites preserved as traces in ancient sediments. The scientists say the evidence shows that trilobites were behaviorally sophisticated, tailoring their attacks for effectiveness.

Kevin Shelton, professor of geological sciences in the MU College of Arts and Science, says in a statement, "The Saint Francois Mountains in southeastern Missouri have been the focus of geological research for decades and were once islands in the Cambrian ocean. I've worked as a geologist studying ore deposits in the area for more than 30 years. In that time, I've run across thousands of fossilized trilobite burrows. It is rare that we get to study the activities of 500 million-year-old organisms, yet the fossils in this locality are helping us determine how these organisms behaved."

Three-dimensional laser scanning and digital photograph analysis of sections of slabs of rocks collected from the site revealed burrows or trails left behind by trilobites and their prey. The trilobite prey were worm-like creatures. The scientists discovered that these intersecting trails show how the predators caught their prey. Previous studies by former MU geology professor, James Stitt, had revealed that the trilobites had very large eyes.

Tracks from the site showed that the predators attacked from above, moving alongside to use their many legs for more effective grappling of their prey. The fossil evidence also shows the trilobites preferentially selected smaller prey. This indicates they attacked their food rather than randomly bumping into it. The graphic above shows a trilobite capturing one of the worm-like creatures.

Schiffbauer says, "Predation, or the action of attacking one's prey, is a significant factor in evolution; this discovery is extremely important in the study of how organisms evolved in the Cambrian Period. In this study, we provide evidence that these trilobites were likely visual predators, displaying selectivity in seeking and hunting their food."

A research paper on the study was published here in the journal, Palaeogeography, Palaeoclimatology, Palaeoecology.

Image: Stacy Turpin Cheavens of the Department of Orthopaedic Surgery, University of Missouri

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