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Plesiosaurs gave birth to live young

From: Ben Creisler

In the new issue of Science, plus news links:

F. R. O?Keefe & L. M. Chiappe (2011) 
Viviparity and K-Selected Life History in a Mesozoic Marine Plesiosaur
(Reptilia, Sauropterygia)
Science333(6044): 870-873 
DOI: 10.1126/science.1205689 

Viviparity is known in several clades of Mesozoic aquatic reptiles, but
evidence for it is lacking in the Plesiosauria. Here, we report a Late
Cretaceous plesiosaur fossil consisting of a fetus preserved within an
adult of the same taxon. We interpret this occurrence as a gravid female
and unborn young and hence as definitive evidence for plesiosaur
viviparity. Quantitative analysis indicates that plesiosaurs gave birth to
large, probably single progeny. The combination of viviparity, large
offspring size, and small brood number differs markedly from the pattern
seen in other marine reptiles but does resemble the K-selected strategy of
all extant marine mammals and a few extant lizards. Plesiosaurs may have
shared other life history traits with these clades, such as sociality and
maternal care. 



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