Anomalocaris is one of the weirdest and fiercest creatures from the Cambrian period, when multicellular life first evolved over 600 million years ago. With its circular, serrated mouth, giant eyes on stalks, spiked arms, and body-spanning fins, this two-meter-long creature was at the top of the food chain in the Earth's ancient seas.
And now it seems, based new fossil evidence, that this killing machine probably had highly accurate, 360 degree vision. Its highly visual hunting style probably changed the course of animal evolution forever.
Image via the Ever So Strange Animal Almanac
A group of scientists found a new fossil of this beast which preserved the structure of its stalked, compound eyes. These eyes, like those of contemporary dragonflies, would have given the Anomalocaris what amounts to wraparound vision with incredibly sharp resolution.
In a release about the study from Nature, editors write:
The fossils represent compound eyes – the multi-faceted variety seen in arthropods such as flies, crabs and kin –and are amongst the largest to have ever existed, with each eye up to 3 cm in length and containing over 16,000 lenses. The number of lenses and other aspects of their optical design suggest that Anomalocaris would have seen its world with exceptional clarity whilst hunting in well-lit waters; only a few arthropods, such as modern predatory dragonflies have similar resolution.
The scientists say that the Anomalocaris' eyes were so complex that it would have needed a brain at least as complex as that of a modern arthropod to process all that visual information. In other words, these creatures were already pretty far along the evolutionary tree before they went extinct. Still, they made a lasting contribution to the evolution of all the creatures they ogled, stabbed, chomped, and ate. Under the Anomalocaris' reign of terror, only creatures who could flee from predators with excellent sight would survive. So if you're wondering why traits like camouflage developed, this could be one reason, since camouflage only works as a survival strategy if you're fleeing from somebody using vision to track prey.
Write the researchers in Nature this week:
The large absolute size and huge number of ommatidial lenses in the eyes of Anomalocaris confirm its status as a highly visual apex predator. The presence of sophisticated nektonic predators with acute vision, such as anomalocaridids, within Cambrian communities would have placed considerable selective pressures on prey that would have influenced the ‘arms race' that began during this important phase in early animal evolution.
In other words, the amazing vision of these monstrous creatures set in motion a vision arms race that has never stopped since.
If you're looking at that picture of the Anomalocaris here and wondering how such a bizarre creature could exist, you're not alone.
Writes Ed Yong over on Not Exactly Rocket Science:
Anomalocaris is no stranger to controversial body parts. It was discovered in a piecemeal fashion, and its various features were thought to be entirely different animals. Joseph Whiteaves found the grasping arms in 1892, and thought them to be the tails of shrimp-like animals (hence the creature's name Anomalocaris, or strange shrimp). Charles Walcott found the ring-shaped mouth separately, and identified it as a jellyfish called Peytoia. Simon Conway Morris found the body and mistook it for a sponge that he named Laggania.
The pieces were, in fact, all part of the same animal, as Harry Whittington and Derek Briggs finally showed. In 1981, they re-examined an earlier fossil to show that the ‘shrimp' and the ‘jellyfish' were actually connected. They finally revealed the animal's true shape in all its weirdness.
Like any great predator, the Anomalocaris is haunted by controversy, even as its deeds echo through the ages.
Read the full story of the Anomalocaris fossils over at Nature