It is well over a C since the first Stegosaurus fossils were draw , and scientists think they have lastly solved one of the great mysteries of the notable dinosaur kinsperson : how to tell the sex activity asunder . The discovery may finally help exploit out another challenging question : how on Earth did these mighty savage have sex ?
Genitalia seldom fossilize well , but for some coinage of dinosaurs it is potential to tell the males from the females in other ways . In certain coinage , specimen show signs of interrupted growth , suspect to cooccur with reproductive wheel . Many sauropods have fused vertebrae that would have help them keep their tails raised . In species such asApatosaurus , this featureonly occurs in half the specimen , suggest it was used by female during mating .
However , for the family known asStegosauridae , named after itsmost famous species , this is not the case . paleontologist have been left to wonder whether one sexual practice was larger than the other or if there is any other way to tell them asunder . The deadly plates on their backs have also raised the dubiousness of how mating could occur withoutone of the partners getting impaled .
However , Evan Saitta , a maestro ’s student at the University of Bristol , noticed that specimens ofStegosaurus mjosicame in two dissimilar types , or morphs . InPLOS One , he reports : “ One morph possessed wide , ellipse plates 45 % larger in airfoil country than the tall , minute plates of the other morph . ” Evidence from other slam sites shew that the plates were not other than shaped at various positions on the eubstance , but consistent throughout an somebody ’s spine .
These were not , Saitta concludes , opposite ends of a spectrum , but make up distinct types with no representatives descend in between . Saitta is also confident that the different morphs are from the same metal money , since a recently unearth quarry in Montana testify at least five specimen that appear to have been swallow up together and were probably living in a societal group . Nor do the difference appear to be a result of age . “ Both morphs take place in fully - grown individual , ” Saitta compose . He established this through CT scan showing that the beast had stopped growing .
Such findings powerfully suggest the two morphs represent male and femaleS. mjosi .
This still result the challenge of working out which morph is which . The conflict seem to have more to do with appearance than practicality . Showy features , such as the peacock ’s tail , are irresistibly more likely to be seen in males of a species than females , and Saitta argues , “ Dinosaur ornamentation possibly served standardized social occasion to the ornamentation of modern species . ” On this base , he guess the larger home plate belonged to the virile Stegosaur stenops and “ Female mate option was likely the drive evolutionary mechanism rather than manful - male competition . ”
It is unusual enough for a master ’s pupil to be the sole generator of a paper in such a prestigious journal , but allot to Bristol ’s Professor Michael Benton , “ Evan made this discovery while he was completing his undergraduate thesis at Princeton University , ” observe something that had eluded the with child dinosaur hunters of the last century . But we still do n’t know how they had sexual activity without the mate getting skewer .
