London, August 23 (ANI): A prototype radula found in 500-million-year-old fossils studied by researchers shows that the earliest radula was not a flesh-rasping terror, but a tool for humbly scooping food from the muddy sea floor.
While the radula sounds like something from a horror movie, it is in fact found in the mouths of most molluscs, from the giant squid to the garden snail.
The Cambrian animals Odontogriphus and Wiwaxia might not have been much to look at - the former a naked slug, the latter a creeping bottom-dweller covered with spines and scales.
Despite the hundreds of fossil specimens collected from the Canadian Rockies by the Royal Ontario Museum, scientists could not agree whether they represented early molluscs, relatives of the earthworm, or an evolutionary dead-end.
I put the fossils in the microscope, and the mouth parts just leaped out, University of Toronto graduate student Martin Smith, author of the study, said.
You could see details you'd never guess were there if you just had a normal microscope, he said.
After examining some 300 fossils, Smith was able not just to reconstruct the mouthparts, but work out how they grew.
The fossils are squashed completely flat, which makes them really hard to reconstruct in 3D, Smith said.
I surrounded myself with micrographs of the mouth parts and lumps of plasticine, and spent weeks trying to come up with a model that made sense of the fossils, he said.
The new observations demonstrated that the mouthparts consisted of two to three rows of 17 similarly-shaped teeth, with a symmetrical central tooth and smaller teeth on the edges.
The teeth would have moved round the end of a tongue in the conveyor-belt fashion seen in molluscs today, scooping food - algae or detritus - from the muddy sea floor.
By establishing how the teeth were arranged, moved, grew, and were replaced, Smith was able to demonstrate that they formed a shorter and squatter forerunner to the modern radula.
The study has been published in the Proceedings of the Royal Society B. (ANI)