{"id":24823,"date":"2016-04-23T02:35:46","date_gmt":"2016-04-23T02:35:46","guid":{"rendered":"https:\/\/new.igihe.com\/clearer-picture-emerging-of-dinosaurs-last-days\/"},"modified":"2016-04-23T02:35:34","modified_gmt":"2016-04-23T02:35:34","slug":"clearer-picture-emerging-of-dinosaurs-last-days","status":"publish","type":"post","link":"https:\/\/new.igihe.com\/english\/clearer-picture-emerging-of-dinosaurs-last-days\/","title":{"rendered":"Clearer picture emerging of dinosaurs\u2019 last days"},"content":{"rendered":"

{Neither a giant asteroid nor a gradual die out can take full blame for dinosaurs\u2019 demise.}<\/p>\n

Rather, the culprit may be both, two new studies suggest.<\/p>\n

Tens of millions of years before the asteroid delivered its killer blow some 66 million years ago, the number of dinosaur species had already begun to drop, researchers report online April 18 in the Proceedings of the National Academy of Sciences. But not all dino groups were in decline, including some maniraptoran dinosaurs, a different group of researchers suggests online April 21 in Current Biology.<\/p>\n

At first glance, the two studies seem to conflict, but \u201cthey can coexist,\u201d says paleontologist Michael Benton, who coauthored the PNAS paper. Both studies add to what has become an increasingly intricate picture of dinosaurs\u2019 final days.<\/p>\n

\u201cThings are a wee bit more complicated than we used to think,\u201d says Benton, of the University of Bristol in England.<\/p>\n

In the 1960s and \u201870s, scientists generally believed that dinosaurs petered out after a long, gradual decline. That view took a U-turn in 1980, when researchers proposed that, instead, an asteroid impact might have suddenly triggered the extinction. \u201cThe flip-flop was quite extreme,\u201d Benton says of the changed thinking. \u201cDinosaurs went from long-term decline to instant death.\u201d<\/p>\n

What actually happened, he says, is probably more nuanced. Benton and colleagues analyzed the number of dinosaur species emerging and going extinct over a huge timescale: roughly 175 million years. Around 40 million to 50 million years before the mass extinction, dinosaurs started losing species faster than they were gaining new ones, the researchers found. This loss in diversity could have made it harder for dinosaurs to bounce back from the asteroid\u2019s catastrophic impact.<\/p>\n

\u201cThis doesn\u2019t in any way attack the importance of the impact,\u201d Benton says. But across the board, he says, dinosaur species numbers were dwindling. At least two groups, however, seemed to buck the trend. Hadrosaurs (duck-billed dinosaurs) and ceratopsids (the group that includes Triceratops) were booming up until the end, the team found.<\/p>\n

According to the Current Biology analysis, toothed maniraptorans (small birdlike relatives of velociraptors) were thriving, too. A detailed examination of more than 3,000 of these dinosaurs\u2019 teeth suggests that these dinos\u2019 ecosystem was pretty stable millions of years before the extinction, says study coauthor Derek Larson, a paleontologist at the Philip J. Currie Dinosaur Museum in Alberta and the University of Toronto.<\/p>\n

Larson and colleagues looked for variations in the teeth\u2019s dimensions, and the size of tooth serrations. Then they determined how much that variation changed over time. Big changes could be a hint that these dinos were on the decline, Larson says. But instead, \u201cthings basically stayed the same through the last 18 million years of the Cretaceous,\u201d he says.<\/p>\n

Toothed maniraptorans \u201cseemed to be doing just fine right up until the extinction,\u201d says University of Oxford paleobiologist Roger Benson, who was not involved in either study.<\/p>\n

Larson\u2019s team wondered why the toothed, meat-eating maniraptorans went extinct after the impact while their relatives \u2014 the beaked ancestors of modern birds \u2014 didn\u2019t. The answer could be dietary, the researchers propose. They analyzed the diets of modern birds to try and figure out what an ancestral bird might have eaten. It probably relied on seeds, Larson says, a hardy food source that could have lasted for decades.<\/p>\n

Seeds might have sustained ancient birds through a \u201cnuclear winter,\u201d the debris-darkened skies that could have blotted out the sun following an asteroid impact. When hoards of plants and animal species died out, and dinosaurs ran out of food, he says, \u201cthe only resource that would have been reliable and available would have been seeds.\u201d<\/p>\n

\"Survival<\/figure>\n","protected":false},"excerpt":{"rendered":"

{Neither a giant asteroid nor a gradual die out can take full blame for dinosaurs\u2019 demise.} Rather, the culprit may be both, two new studies suggest. Tens of millions of years before the asteroid delivered its killer blow some 66 million years ago, the number of dinosaur species had already begun to drop, researchers report […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14],"tags":[75],"byline":[2491],"hashtag":[],"class_list":["post-24823","post","type-post","status-publish","format-standard","hentry","category-environment","tag-homenews","byline-science-daily"],"bylines":[{"id":2491,"name":"SCIENCE DAILY","slug":"science-daily","description":"","image":{"id":0,"url":"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&f=y&r=g","alt":"Default avatar","title":"Default avatar","caption":"","mime_type":"image\/jpeg","sizes":[]},"user_id":null}],"contributors":[{"id":2491,"name":"SCIENCE DAILY","slug":"science-daily","description":"","image":{"id":0,"url":"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&f=y&r=g","alt":"Default avatar","title":"Default avatar","caption":"","mime_type":"image\/jpeg","sizes":[]},"user_id":null}],"featured_image":null,"_links":{"self":[{"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/posts\/24823","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/comments?post=24823"}],"version-history":[{"count":0,"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/posts\/24823\/revisions"}],"wp:attachment":[{"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/media?parent=24823"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/categories?post=24823"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/tags?post=24823"},{"taxonomy":"byline","embeddable":true,"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/byline?post=24823"},{"taxonomy":"hashtag","embeddable":true,"href":"https:\/\/new.igihe.com\/english\/wp-json\/wp\/v2\/hashtag?post=24823"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}