Giant fossils from a newfound trilobite species, Redlichia rex, have been unearthed on Kangaroo Island, South Australia, providing crucial insights into the Cambrian explosion—a pivotal period in Earth's history marked by a surge in diverse animal groups over half a billion years ago.
Trilobites, characterized by hard, calcified skeletons, akin to modern crustaceans and insects, thrived for approximately 270 million years. Redlichia rex, named for its colossal size and formidable legs equipped with spines for crushing and shredding, was discovered by James Holmes, a Ph.D. student at the University of Adelaide's School of Biological Sciences.
The unique preservation of soft parts, including antennae and legs, is exceptionally rare but was made possible by the Emu Bay Shale on Kangaroo Island—a renowned site for such preservation. Described in the Journal of Systematic Palaeontology, this 500-million-year-old species stands out as the largest Cambrian trilobite discovered in Australia, measuring about 30 cm in length, nearly twice the size of contemporaneous Australian trilobites.
Holmes remarked, “The overall size and crushing legs of Redlichia rex are a likely consequence of the arms race that occurred at this time.” The Cambrian explosion saw an evolutionary “arms race” between predators and prey, prompting the development of defense mechanisms like shells. Injuries observed in trilobite specimens, possibly from shell-crushing predators, and the presence of fossilized coprolites with trilobite fragments in the deposit hint at the intense ecological interactions of the time.
Associate Professor Diego García-Bellido, a senior study author from the University of Adelaide and the South Australian Museum, noted, “The large size of injured Redlichia rex specimens and the associated coprolites suggests that either much bigger predators were targeting Redlichia rex, such as Anomalocaris—an even larger shrimp-like creature—or that the new species had cannibalistic tendencies.”
The fossilized remains, including Redlichia rex and other specimens from Emu Bay Shale, are on display at the South Australian Museum, offering a glimpse into the ancient marine ecosystem and the intricate dynamics of predator-prey relationships during the Cambrian period.
Source: University of Adelaide