The earliest predators to have terrorized the planet over 500 million years ago were also believed to be the largest animals to have lived at the time. However, a new fossil study led by Jianni Liu from the Northwest University of Xi’an in China, has shown that their tiny babies were also proficient killers.
The Arthropoda animal group with its modest human term “creepy crawly”, comprising of spiders, insects and crustaceans, is part of one of the most popular interpretations of vicious monsters in science fiction media due to their terrifying appendages. Some of the oldest and most primitive arthropod species belong to a group called the Radiodonta (“radiating teeth”), which were armed with large, spiny raptorial (or grasping) appendages at the front of the head and a circular mouth adorned with tooth-like serrations. These animals, including the famous Anomalocaris, are considered the giant apex predators of their time, reaching lengths of over one metre. Looks like the movies weren’t lying after all!Knowledge on the predators of the past was fairly cloudy in recent years so it is no surprise that virtually nothing was known about the offsprings of these ferocious beings. The feeding habits and biology of these creatures was of major interest to scientists for decades and their questions were recently answered by the discovery of an exceptionally-preserved juvenile of a species called Lyrarapax unguispinus from the early Cambrian (518 million-year-old) Chengjiang biota of China. This has shed light on this intriguing group of fossil arthropods paving way for further research and findings.
At only 18mm in total body length, this almost complete specimen represents the smallest radiodontan ever found. During the course of the research, scientists made an astounding discovery on the anatomy of the predators. The structure of these creatures is extraordinarily well developed–especially the spiny grasping appendages–giving it the appearance of a miniaturized adult. The findings conclude that Lyrarapax unguispinus was an efficiently equipped predator with a progressed development similar to modern arthropods such as praying mantises, mantis shrimps, and arachnids. This discovery confirms that raptorial feeding habits in juveniles appeared early on in the evolutionary history of arthropods.
This fossil find also has important implications for the rapid evolution of the first predators over half-a-billion years ago – an event referred to colloquially as the Cambrian ‘Explosion’. It is hypothesized that predation was a major driver of progressed evolution, with predators placing selective pressures on animal communities, forcing prey species to adapt and evolve or face extinction. The lifestyle of radiodontan “babies” adds further convolutions to the Cambrian marine food webs by subjecting small prey species to additional pressure during this evolutionary ‘arms race’.