Bite the dust: Meek di­nosaur lost its teeth

Kuwait Times - - HEALTH & SCIENCE -

WASH­ING­TON: A mod­est lit­tle di­nosaur that scam­pered across north­west­ern China 160 mil­lion years ago boasted a unique trait not seen in any other di­nosaur or other pre­his­toric crea­ture yet un­earthed: it was born with teeth but be­came tooth­less by adult­hood. Sci­en­tists on Thurs­day said fos­sils of 19 in­di­vid­u­als of a di­nosaur called Limusaurus, rang­ing in age from un­der a year to 10 years, showed that ju­ve­niles had small, sharp teeth but adults de­vel­oped a tooth­less beak.

This clus­ter of di­nosaurs, found in Xin­jiang Prov­ince, ap­par­ently be­came hope­lessly trapped in a mud pit and died. Only rarely have sci­en­tists found fos­sils of a di­nosaur species rang­ing from ba­bies to adults, a se­quence re­veal­ing var­i­ous anatom­i­cal changes that un­fold as an an­i­mal ma­tures. Limusaurus was a lightly built two-legged di­nosaur with short arms and long, slen­der legs. It may have had down-like feath­ers cov­er­ing at least part of its body. The largest ones were about 6 feet long (un­der 2 me­ters).

“It prob­a­bly looked some­thing like an emu with a long tail,” said Ge­orge Wash­ing­ton Univer­sity pa­le­on­tol­o­gist Joey Stiegler, one of the re­searchers in the study pub­lished in the jour­nal Cur­rent Bi­ol­ogy. Such tooth loss is called on­to­ge­netic eden­tulism. Some an­i­mals alive to­day have it, in­clud­ing the egg-lay­ing Aus­tralian mam­mal the platy­pus. The adult Limusaurus in­di­vid­u­als also were found with stones called gas­troliths that some plant-eat­ing di­nosaurs swal­lowed to grind up plant ma­te­rial in the stom­ach. The ba­bies lacked these.

The tooth loss and gas­troliths in­di­cate Limusaurus un­der­went a dra­matic di­etary change from birth to adult­hood, start­ing life per­haps eat­ing in­sects and small ver­te­brates be­fore later turn­ing to plants. Limusaurus is a mem­ber of the thero­pod di­nosaur group within which birds evolved.—Reuters

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