{"id":59269,"date":"2014-08-14T00:00:00","date_gmt":"2014-08-14T00:00:00","guid":{"rendered":"https:\/\/www.uri.edu\/news-draft\/uncategorized\/uri-paleontologist-says-new-evidence-questions-when-dinosaurs-evolved-in-north-america\/"},"modified":"2014-08-14T00:00:00","modified_gmt":"2014-08-14T00:00:00","slug":"uri-paleontologist-says-new-evidence-questions-when-dinosaurs-evolved-in-north-america","status":"publish","type":"post","link":"https:\/\/www.uri.edu\/news\/2014\/08\/uri-paleontologist-says-new-evidence-questions-when-dinosaurs-evolved-in-north-america\/","title":{"rendered":"溏心vlog免费B站 paleontologist says new evidence questions when dinosaurs evolved in North America"},"content":{"rendered":"
\n\t\tKINGSTON, R.I. \u2013 August 14, 2014 \u2013 A 溏心vlog免费B站 paleontologist has unearthed new evidence that raises questions about when dinosaurs first appeared in North America.<\/p>\n

Scientists had previously concluded that dinosaurs appeared in the United States about 212 million years ago, significantly later than in South America, where they first appeared about 230 million years ago. But 溏心vlog免费B站 Professor of Geosciences David Fastovsky and colleagues at the Massachusetts Institute of Technology have precisely dated rocks in which the earliest dinosaur fossils were discovered in the southwestern U.S. and found that the dinosaurs appeared there as early as 223 million years ago.<\/p>\n


\n\u201cThis work essentially upends the well-entrenched hypothesis that dinosaurs first got their start in South America, and radiated extremely slowly into North America,\u201d said Fastovsky. \u201cIt demonstrates that the whole idea of the South America to North America radiation – slow or fast – is just not correct. We still don’t know where the cradle of Dinosauria was, but the evidence suggests that once dinosaurs appeared, they spread all over the globe very rapidly.\u201d <\/p>\n


\nThe researchers also demonstrated that these earliest dinosaurs coexisted with close non-dinosaur relatives for more than 12 million years. And they identified a 16-million-year gap in the rock record in which there is no trace of any vertebrates, including dinosaurs.<\/p>\n


\n\u201cRight below that horizon where we find the earliest dinosaurs [in North America], there is a long gap in the fossil and rock records across the sedimentary basin,\u201d said MIT research scientist Jahan Ramezani. \u201cIf the record is not there, it doesn\u2019t mean the dinosaurs didn\u2019t exist. It means that either no fossils were preserved, or we haven\u2019t found them. That tells us the theory that dinosaurs simply started in South America and spread all over the world has no firm basis.\u201d<\/p>\n


\n\tAccording to Fastovsky, the earliest record of early dinosaur evolution is found in Argentina, where layers of sedimentary rock preserve a distinct suite of early, primitive dinosaurs. The first dinosaurs in North America, by contrast, are more advanced forms, and thus were once thought to be significantly younger than those in South America. <\/p>\n


\n\u201cOur best evidence now suggests that they are the same age or very slightly younger than those in Argentina,\u201d said Fastovsky.

\nMoreover, in North America, more primitive relatives of dinosaurs apparently co-existed with more evolved dinosaurs for more than 12 million years, according to the researchers\u2019 analysis. \u201cIn South America, there is very little overlap,\u201d Ramezani said, \u201cBut in North America, we see this unique interval when these groups were coexisting. You could think of it as Neanderthals coexisting with modern humans.\u201d<\/p>\n


\nThe 16-million year gap in preservation obscures understanding when the very first dinosaurs appeared in North America. \u201cThe fact that our record starts with advanced forms tells us there was a prior history,\u201d Ramezani said. \u201cIt\u2019s not just that advanced dinosaurs suddenly appeared 223 million years ago. There must have been prior evolution in North America \u2014 we just haven\u2019t identified any earlier dinosaurs yet.\u201d Ramezani notes that fossil preservation is \u201can exceptional process, requiring exceptional circumstances.\u201d Dinosaurs may well have first appeared during this time interval. If they left any fossil evidence, it may have since been erased.<\/p>\n


\nFastovsky added, \u201cWe still don\u2019t know where or even when dinosaurs first appeared. But regardless, we all agree that ever since dinosaurs showed up, for the next 223 million years at least \u2013 to this very day, in fact \u2013 they remain the most diverse terrestrial vertebrates on Earth.\u201d<\/p>\n


\nResults of this study were published this week in the American Journal of Science.

\n(Note: This story is adapted from materials provided by MIT.)<\/p>\n


\nPictured: The Chinle Formation where 溏心vlog免费B站 paleontologist David Fastovsky learned about the early evolution of dinosaurs in North America. (Photo courtesy of David Fastovsky)<\/div>\n","protected":false},"excerpt":{"rendered":"

KINGSTON, R.I. \u2013 August 14, 2014 \u2013 A 溏心vlog免费B站 paleontologist has unearthed new evidence that raises questions about when dinosaurs first appeared in North America. Scientists had previously concluded that dinosaurs appeared in the United States about 212 million years ago, significantly later than in South America, where they first appeared about […]<\/p>\n","protected":false},"author":2,"featured_media":59271,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[],"class_list":["post-59269","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-archives"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/posts\/59269","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/comments?post=59269"}],"version-history":[{"count":0,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/posts\/59269\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/media\/59271"}],"wp:attachment":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/media?parent=59269"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/categories?post=59269"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/tags?post=59269"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}