More than half a billion years ago, during the Cambrian Period, Earth was reigned by primitive arthropods, distant ancestors of today’s crustaceans, insects, and spiders. Among the oldest species of arthropods were a group called the Radiodonta. These creatures were so fierce that they were named after their scariest feature — their radiating teeth.
Radiodontas were the most ferocious predators of their time and prowled the oceans in search of prey, which they snatched up with large, spiny limbs called raptorial appendages. Placed at the front of their heads, these grasping limbs were used to pull prey into the radiodontas’ circular mouths, which were filled with tooth-like serrations.
The fiercest of them all was Anomalocaris (pictured above and in the video below), an apex predator and one of the largest creatures of the Cambrian, reaching lengths of more than 3.2 feet.
If its size doesn’t strike you as particularly impressive, you should note that before the Cambrian Period, which lasted between 543 million and 493 million years ago, most life forms were aquatic plants and primitive multicell organisms.
And, as it turns out, baby radiodontas were equally terrifying. A new study published on June 1 in the National Science Review uncovered that radiodontas didn’t have to wait until they reached adulthood to become skilled, voracious predators.
The research, conducted by an international team of scientists from China, Australia, and Germany, examined a 518-million-year-old fossil belonging to a juvenile radiodontan and found that the tiny offspring of these extinct creatures were also proficient killers, EurekAlert reports.
The fossil, which dates back to the early Cambrian, is spectacularly well-preserved and belongs to an ancient species known as Lyrarapax unguispinus, an arthropod from the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans.
Discovered in the famous Chengjiang UNESCO World Heritage Site in China, the fossil, which was unearthed nearly complete, only measures 18 millimeters (about 0.7 inches) in length.
This makes it the smallest radiodontan ever known, reveal the researchers, led by Jianni Liu from the Northwest University of Xi’an in China.
A study of its anatomy showed that the juvenile L. unguispinus was the spitting image of its parents. The babies of the species were very well developed and even had the spiny raptorial appendages that the adults sported.
This discovery “indicates that L. unguispinus was a well-equipped predator at an early developmental stage, similar to modern raptorial euarthropods, such as mantises, mantis shrimps, and arachnids,” the authors write in their paper.
More to the point, it “confirms that raptorial feeding habits in juvenile euarthropods appeared early in the evolutionary history of the group,” the study concludes.
This revelation sheds new light into the fast evolution of species during the “Cambrian Explosion,” an event that took place roughly 541 million years ago and gave rise to most of the major animal groups on the planet.
Scientists have theorized that the “Cambrian Explosion” was fueled by predation, which forced many animals to adapt and evolve in order to evade their predators.
Because baby radiodontas, the giant predators of the Cambrian, were also actively hunting for prey, they put additional pressure on smaller species. This, in turn, may have played a part in the rapid bloom of life emerging from the “Cambrian Explosion,” notes EurekAlert.