Did giant dinosaurs take baby steps?

Scientists have long known that the giant, four-legged sauropods-—like the Science Museum's Diplodocus-—evolved from earlier, two-legged species. But exactly how has been a mystery. A scientist at the Smithsonian thinks he's found the answer.

Dr. Hans Sues has studied eggs and babies of the two-legged dinosaur Massospondylus (MASS-oh-SPON-dih-lus). The fossils showed that babies walked on all four legs, and switched to the two-legged adult gait at age two or three years. Sues suggests that later species retained the juvenile feature, and stayed on four legs their entire lives. This evolutionary process is called neotony.

Not everyone is convinced, though. The Science Museum's Kristi Curry Rogers, a world expert on sauropods, thinks Massospondylus was not an ancestor to the later giants.

(Neotony—the process of retaining juvenile traits into adulthood—is a well-documented evolutionary phenomenon. In fact, it may have occurred in humans! Adult humans have many traits that are found in young apes, but disappear as the animal grows up—things like a flat face, little hair, large head, and a neck directly beneath the skull rather than behind it. Some scientists believe that, as out species evolved away from the apes, we developed more slowly, so that adult humans retain these features, while adult apes outgrow them. In fact, Aldous Huxley once wrote a novel based on the premise that, if a person lived long enough, they eventually would develop into an ape! Pure fiction, but a fun idea!)

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

Hmm, i always thought plateosaurus was that breakthrou.

posted on Sun, 01/29/2006 - 3:08pm
Gene's picture
Gene says:

Plateosaurus was an early dinosaur, part of a group known as the prosauropods. They have long necks and tails like the later sauropods -- giant, four-legged dinosaurs like Diplodocus -- but Plateosaurus walked on two legs.

For a long time, scientsts thought that prosauropods were the ancestors of sauropods. But recently, some have started to question that assumption. Prosauropods have some specialized features, especially in their hands, that sauropods do not share. This has led some researchers to conclude that sauropods did not evolve from prosauropods -- instead, the two groups are separate branches on the dinosaur family tree that share a common ancestor.

posted on Mon, 01/30/2006 - 3:33am

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