Cannibalism Is More Ancient Than Thought, Trilobite Fossils


Cannibalism is common among millions of modern arthropod species. Praying mantis consumes its mate after mating, termites suck blood from wounded peers and mosquitoes Junk food on the larvae. But how far back does this eerie style of eating go in the life-feeding history of life?

Previous studies, earliest cannibalism About 450 million years ago in the Late Ordovician period. However study Earlier evidence of cannibalism may be found in a 514-million-year-old trilobite treasure at a place called Emu Bay, on an island off the coast of South Australia, Paleoecology, published last month in the journal Paleoclimatology. There, ancient wounds on trilobite shells abound, and fossil excrement possibly produced by trilobites contains even more trilobite shells. These imply that cannibalism may be dated to the early Cambrian period, 50 million years earlier than previously thought.

Paleontologists think the best evidence that one animal consumed another is a meal preserved in the fossilized intestines. However, such fossils are rare.

But the area in Emu Bay was optimal for preserving a different kind of evidence of who ate who: fossilized wounds and fossilized feces.

Trilobites have hard exoskeletons like modern crustacean arthropods – think horseshoe crabs or lobsters. As the trilobites survived the attacks, their shells recorded these close calls with bite marks, crushed segments, and missing pieces.

In the new study, Russell Bicknell, a paleontologist at the University of New England in Australia, focused on healing injuries in two trilobite species from Emu Bay: Redlichia takooensis and Redlichia rex. Dr. Bicknell collected 38 fossils of two species from Emu Bay, some from fieldwork and others in the South Australian Museum collection. While examining the fossils, Dr. Bicknell checked for patterns that could tell him about their attack style and therefore who the attacker was.

Specimens with healed wounds—trilobites that survived attacks, including R. rex—were large, so something even bigger must have attacked them. Little trilobites with scars were nowhere to be seen, and Dr. Bicknell had a doubt as to where they would end up: in fossilized excrement, also known as coprolith.

Coprolites in Emu Bay were large, at least 10 percent the length of an adult trilobite’s body. Dr. Bicknell said it’s often impossible to tell which species a shell fragment came from, but the researchers are confident that the coprolite fragments reflect the two species in the study.

“Anything smaller is consumed and turned into these cute coprolites,” he said. “Anything bigger takes something from it, but it managed to evade the attack.”

He estimated that the attacker was most likely R. rex, which grew to around 10 inches in length.king trilobite“its age. Dr. Bicknell describes the R. rex as “horseshoe crab, but on steroids.” He sees it making rapid progress on the Cambrian seafloor, preying on easy, small targets, including smaller members of its own species.

Hence, Dr. If R. rex produced the excrement, as Bicknell suspected, the slaughter at Emu Bay represents the earliest example of cannibalism in the fossil record.

Loren Babcock, a paleontologist at Ohio State University who has studied trilobite predation for decades, said he hopes similar-scale studies will be conducted elsewhere to look for similar patterns or signs of predation, and perhaps even gut contents. X-rays and micro-CT scans. Whether trilobites made coprolites is “an open question, but trilobites are a good guess for now,” he said.

Dr. Babcock added that he would be surprised that no trilobites were cannibals. But at the same time, another predator of the Cambrian period, Anomalocaris, was discovered by Dr. He thought it possible that Bicknell produced some of the coprolites used in his study in Emu Bay.

Dr. Bicknell suspects that Anomalocaris, despite its size, was capable of crushing trilobites with its spindly appendages.

Allison Daley, a University of Lausanne paleontologist who was not involved in the study, said the size of the coprolites in Emu Bay helped convince her that large trilobites such as R. rex may be responsible for the region’s predation.

“There aren’t many things big enough to make these coprolites,” he said.

But he added that trilobites are unlikely to be fully cannibals.

“Let’s face it, if you could find something to eat that wasn’t mineralized,” he said, referring to trilobite shells, “you’d probably eat it.”

A completely cannibalistic species doesn’t last very long.



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