Researchers find first evidence of venom system in extinct mammal

06/21/05

A tiny fossil found more than 10 years ago in central Alberta has proved to be the key to answering a long unsolved evolutionary question, say researchers from the University of Alberta.

Back in 1991, Dr. Richard Fox and his research team found a 60 million year-old incomplete skull fossil that they now believe is the first evidence of an extinct mammal with a venom delivery apparatus. The research will be published June 23, 2005 in Nature.

"Our discovery shows that mammals have been much more flexible in the evolution of venom delivery systems than previously believed," said Fox, who works out of the Laboratory for Vertebrate Paleontology in the U of A Department of Biological Sciences.

About the size of a mouse, the ancient mammal--Bisonalveus browni--may have resembled a small hedgehog or a small mole, but it isn't related to any animal that currently exists, said Craig Scott, a PhD student at the U of A and co-author of the paper in Nature.

Currently, there are two types of living mammals with salivary venom-injecting capabilities: the Caribbean Solenodon (found primarily in Cuba) and the North American short-tailed shrew.

The fossil that Fox's research team found expressed a deep groove in the upper canines, and, Fox noted, the groove resembled the grooved poison fangs found in some kinds of modern venomous snakes. He added that the fact that the walls of the groove are covered with enamel indicates the groove is not a product of post-mortem exposure and splitting but rather is the natural design of the tooth. "The groove in these teeth would have acted as a gutter, conducting fluid from its source in glandular tissues in the upper jaw down the height of the crown to its tip," Fox explained.

"When I first saw [the groove] I thought maybe it was a cavity," said Yong-Qin Sun, the lab technician who prepared the fossil, which is one of thousands that the U of A researchers have collected over the years from the banks of the Blindman River near Red Deer, Alberta.

Sun immediately took the fossil to Scott, who thought it was the first proof of a venomous capacity in an extinct mammal, but he took it to Fox to confirm his notion.

Fox and Scott had found individual canine fossils with similar grooves, but they didn't know which species of animal the loose fossils came from. The Bisonvaleus browni fossil was the first time they had seen teeth like this preserved within an intact upper and lower jaw, which is extremely rare for a specimen this old.

"This just shows you that no matter how long you've been working on something, you can still learn a lot just by uncovering one little piece of information," Fox added. "And we're fortunate that we are able to work where we do; central Alberta is one of the richest areas of the world to uncover the types of fossils that we're interested in."

Source: Eurekalert & others

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