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Dinosaur bones shed light on development

An embryonic cross section of a thigh bone from Lufengosaurus, a gigantic long-necked herbivore.

A. LeBlanc/University of Toronto

An embryonic cross section of a thigh bone from Lufengosaurus, a gigantic long-necked herbivore.

LOS ANGELES — Recently discovered dinosaur embryos are giving scientists their best glimpse yet into how the ancient creatures developed.

The 190-million-year-old fossils unearthed in China ­belonged to Lufengosaurus, a long-necked plant eater known for its gigantic size, with adults 30 feet long.

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A detailed look at more than 200 bones from 20 animals at various stages of development reveal they grew much more rapidly in the egg than other dinosaurs and flexed muscles in much the same way as birds and humans.

While not a complete surprise, “we are thrilled that we could document this for the first time for an extinct animal,” said University of Toronto paleontologist Robert Reisz, who led an international team.

The embryos were the same age as a separate set of fossils that Reisz reported about in 2005 from South Africa and were hailed at the time as the oldest dinosaur embryos ever found. The two types of dinosaurs, which roamed during the early Jurassic age, were close relatives.

The discovery was published in Thursday’s Nature. The cache of bones was uncovered three years ago, but it has taken this long to analyze them — not an unusual lag time for ­dinosaur finds.

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