Giant lizard's size helped it and hurt it

Q: At a Buenos Aires museum is a single dinosaur vertebra from 100-million-year-old Argentinosaurus, measuring 5 feet, 3 inches high and requiring a forklift truck to move it. A human vertebra, by comparison, would fit in the palm of a hand, an elephant's would take two hands. So how did this biggest land animal ever get to be so big?

A: The Argentine lizard weighed in at 75-100 tons and was 70 feet tall and 115 feet long, says James O'Donoghue in New Scientist magazine.

Cope's rule argues that animals often start out small and get bigger over evolutionary time, with obvious advantages, says paleontologist Martin Sander: it's harder for anything else to eat them and they're better equipped to fight off competitors for food or mates. However, big animals are more vulnerable to extinctions, notes paleontologist David Hone. They eat more and breed more slowly, which can do them in when times get tough.

Giant sauropods like the Argentine lizard probably needed to eat a ton of vegetation a day, which they did by having long necks and small heads with enormous feeding range. Instead of chewing, they swallowed foods whole, allowing them to go without huge grinding teeth and elaborate musculatures. The nutrients could have been extracted by internal microbial fermentation, all of which helped these sauropods become a fixture of the dinosaur age for 145 million years.

Q: How might lightning knock down a whole group of people, such as the players in a baseball game?

A: You're most familiar with a direct solo hit, which can send a large amount of current through the chest, stopping the heart, paralyzing the muscles required for breathing, and causing internal burns, says Jearl Walker in "The Flying Circus of Physics." A more subtle way of injury or death lies in the "ground current," or lightning current along the surface.

If the victim stands with one foot closer to the strike point than the other, the ground current can detour up one leg, across the torso, and down the other leg. If the amount of current is small, the victim might suffer only temporary paralysis.

In some cases, ground current can knock down several people at once, including baseball players. Cows, horses and sheep are usually in more danger from such current because their front legs and hind legs are well separated, resulting in a greater amount of ground current directed across the body.

"People can stand with feet together but sheep cannot."

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© Bill Sones and Rich Sones, Ph.D.