December 8, 2011
Oldest Super Predator Had Highly-acute Vision
Paleontologists working on fossils from Kangaroo Island in South Australia have discovered that the Earth's first apex predator had highly acute vision that rivaled or exceeded that of most living insects and crustaceans.
The researchers from South Australian Museum and University of Adelaide discovered exceptionally preserved fossil eyes of the top predator in the Cambrian ocean from over 500 million years ago: the fearsome Anomalocaris.
The species is considered to be at the top of the earliest food chains because of its large body size, formidable grasping claws at the front of its head and a circular mouth with razor-sharp serrations. Supporting evidence of this predator's dominance includes damage to contemporaneous trilobites, and even its fossilized excrement (or coprolites) containing the remains of its prey.
The discovery of its stalked eyes - showing remarkable details of its optical design - confirms the creature had superb vision to support its predatory lifestyle, the researchers said.
The fossils represent compound eyes of the multi-faceted variety seen in arthropods such as flies, crabs and kin, and are among the largest to have ever existed, with each eye more than 1 inch 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 while hunting in well-lit waters. Only a few arthropods, such as modern predatory dragonflies, have similar resolution.
The existence of highly sophisticated, visual hunters within Cambrian communities would have accelerated the predator-prey 'arms race' that began during this important phase in early animal evolution over half a billion years ago.
The discovery of powerful compound eyes in Anomalocaris confirms it is a close relative of arthropods, and has other far-reaching evolutionary implications.
It demonstrates that this particular type of visual organ appeared and was elaborated upon very early during arthropod evolution, originating before other characteristic anatomical structures of this group, such as a hardened exoskeleton and walking legs.
The findings are published in the December 8 issue of the journal Nature, which includes an artist's impression of the super predator on the front cover.
Image Caption: The meter-long super predator Anomalocaris. Artist's impression by Katrina Kenny/University of Adelaide.
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