Courtesy of Nature

The largest and most diverse group of Triassic aquatic reptiles gave birth to live young, researchers recently reported.1 The finding represents the first evidence of viviparity in sauropterygians, which lived throughout the Mesozoic era, from 250 to 65 million years ago. The evidence came in the form of two small, nearly complete, pregnant specimens of Keichousaurus hui, a sauroptery-gian found in the Guizhou province of southwestern China. The females settle a long-time debate about whether this group was oviparous or viviparous, says Xiao-chun Wu, an author on the study at the Canadian Museum of Nature.

"These two specimens speak very nicely, very neatly, and very cleanly ... that the ability to give birth to live young arose very early on in the evolution of these groups of reptiles," says Michael Caldwell of the University of Alberta. The specimens offer clues for discerning the sex of...

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