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Baby dinosaurs took three to six months to hatch

Fossils show dinos had incubation times more similar to reptiles than birds

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3:10pm, January 23, 2017
Protoceratops andrewsi

SLOW GROW  This 75-million-year-old hatchling fossil of the dinosaur Protoceratops andrewsi was found in Mongolia. Fossilized P. andrewsi embryos reveal dinos had reptilelike incubation times.

Dinosaurs might live on today as birds, but they hatched like reptiles. Developing dinos stayed in their eggs three to six months before emerging, far longer than previously suspected, researchers report online January 3 in the Proceedings of the National Academy of Sciences.

With few clues to dinosaurs’ embryonic lives, scientists assumed that young dinosaurs shared modern birds’ swift incubation period, which ranges from 45 to 80 days for eggs in the size range of dino eggs. A reptile egg generally takes about twice as long to hatch as a bird egg of similar size, says lead author Gregory Erickson, a paleobiologist at Florida State University in Tallahassee.

But counts of growth lines on the teeth of rare fossilized dinosaur embryos from two species, Protoceratops andrewsi and Hypacrosaurus stebingeri, suggest a longer trajectory like that of reptiles, say

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