Venomous Bite Of A Mammal


July 01, 2005|By William Mullen | William Mullen,CHICAGO TRIBUNE

Sorting through boxes of fossils collected 14 years ago, a Canadian doctoral student discovered the deadly, poisonous bite of a 60 million-year-old mammal the size of a mouse.

The first "venom delivery apparatus" ever found in an extinct mammal was described last week in the research journal Nature by the student, Craig Scott, and his professor, vertebrate paleontologist Richard C. Fox of the University of Alberta, Edmonton.

Its discovery may shed new light on the reason why mammals, unlike reptiles, seldom evolved to use poisonous bites for predation and protection. Only two modern mammals have a poisonous bite: certain shrews and the almost extinct solenodon, a primitive, long-snouted, insect-eating mammal native to Cuba, Haiti and the Dominican Republic.

"Our discovery shows that mammals have been much more flexible in the evolution of venom delivery systems than previously believed," Fox said Wednesday.

Why more mammals didn't continue to use poison into the modern era remains a mystery, he said.

The species, Bisonalveus browni, has been known since 1956 when partial fossils of the animal, thought to resemble a small hedgehog or mole, were found in Wyoming. The jaw bones of those discovered were only partial, containing back teeth but not the front incisor and canine teeth.

In 1991, Fox led a collecting expedition for fossils in 60 million-year-old rock formations of the late Paleocene period along the banks of Blindman River near Red Deer, Alberta. The expedition returned with numerous specimens, Fox said, that were stored at the university to await examination.

Nobody got back to the fossils for 14 years, until Fox assigned one of his doctoral students, Scott, to examine and describe the 1991 specimens for his thesis.

A lab technician, Yong-Qin Sun, who was helping to remove the rock from the fossilized bones, first noticed the upper front canine teeth on the recovered jaw of Bisonalveus browni. Puzzled by the long grooves running the length of the teeth, she showed them to Scott.

"When I first saw the groove I thought it was a cavity," said Sun.

Scott said he saw the groove as a system for delivering venom.

"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," he said.

His mentor, Fox, agreed. The animal could have delivered poison like many snakes, sending a spurt of toxic fluid down the tooth as it clamped into its victim's flesh, said Fox, or "it could have worked like the modern Gila monster, which chews on its prey to distribute the venom into the flesh."

The Chicago Tribune is a Tribune Publishing newspaper.

How to slim down with less on plate

The Portion Teller: Smartsize Your Way to Permanent Weight Loss (Morgan Road Books, $19.95).

Nutritionist Lisa R. Young, who appeared in the award-winning documentary Super Size Me, is onto something: It's not what you eat, but how much you eat, that matters.

In her new book The Portion Teller, Young explores how outrageous our food portions have become. Today, a 7-Eleven Double Gulp drink has 800 calories. A bagel and pizza slice may contain enough calories for an entire day - and that's not counting the cream cheese.

Such portions, which have grown larger over time, have helped fuel the nation's obesity problem, Young says.

She shows readers how to return to sensible eating. Your daily meat portion, for example, should be the size of a deck of cards. A cereal serving should be baseball-sized. And you should use a shot-glass worth of salad dressing on your lettuce.

Young doesn't promise overnight results in this sensible, well-designed book. Instead, she gives you a way to return to reasonable portions.

Bottom Line: This book is worth reading if you're trying to buck the trend toward larger and larger portions.

- Mary Beth Regan

In Brief

Doctors report birth from frozen ovarian tissue

A 28-year-old woman gave birth to a healthy baby girl after an ovarian tissue transplant reversed infertility caused by cancer treatment, doctors in Israel are reporting.

Last year, a Belgian woman gave birth after such an operation, but the claim was controversial because the egg could have come from her remaining ovary, not the transplanted tissue.

The case reported Monday by Dr. Dror Meirow of Sheba Medical Center in Tel Aviv is more convincing because menopause was documented for two years before the transplant. The New England Journal of Medicine reported the case on the Internet and says it will publish it in its July 21 issue.

Doctors froze ovarian tissue from the woman before she had high doses of drugs for non-Hodgkin's lymphoma. Two years later, lab tests showed she remained infertile. Strips of her frozen tissue were attached to her left ovary and fragments of it were injected into the right one.

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