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5 December 2013 11:26 am ,
Vol. 342 ,
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Nothing to Bite On
4 January 2002 (All day)
Lampreys and other living relatives of primitive vertebrates don't have jaws. But that doesn't mean they're mild-mannered vegetarians; some attack their prey of fish with the fury of a wolverine. Equally nasty were the eel-shaped conodonts, an extinct jawless fish. These and other observations have led some researchers to propose that jaws evolved in response to increasingly aggressive hunting habits by jawless ancestors. But a new study takes a bite out of this widespread idea.
Mark Purnell of the University of Leicester, United Kingdom, tested the notion by looking at the heterostracans, a group of extinct jawless fishes that were a dominant slice of vertebrate life for 140 million years until they went extinct at the end of the Devonian. They were relatives of the conodonts, and they shared a more recent common ancestor with the first jawed fish. Some researchers argue that the heterostracans were predators.
In the 7 January issue of the Proceedings of the Royal Society, however, Purnell argues that they were better suited for filter feeding. Using an electron microscope, Purnell took a close look at the oral plates that line the mouth. The plates were not worn on their tips, as one would expect if they had bit into prey. And they were covered with denticles not much more than 100 micrometers long and delicately shaped like triangles and maple leafs. "If this animal tried to grab hold of prey, the denticles would get broken," he says. Moreover, because the denticles pointed toward the front of the mouth, they would have prevented anything other than microscopic food from entering.
Philippe Janvier of the National Natural History Museum in Paris says the study presents "the first good evidence of filter feeding in these early jawless fossil vertebrates."