{"id":19211,"date":"2016-06-13T00:00:00","date_gmt":"2016-06-13T00:00:00","guid":{"rendered":"https:\/\/kus.edu.iq\/mammals-information-scintific\/"},"modified":"2023-11-19T05:10:54","modified_gmt":"2023-11-19T05:10:54","slug":"mammals-information-scintific","status":"publish","type":"post","link":"https:\/\/kus.edu.iq\/old\/en\/mammals-information-scintific\/","title":{"rendered":"(mammals (information scintific"},"content":{"rendered":"
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Mammals experienced a boom in diversity long before the dinosaurs became extinct 66 million years ago, overturning 
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the notion that their evolution was curbed by the success of the land-based reptiles, scientists have said.<\/span><\/div>\n
It has long been thought that dinosaurs kept diversity among mammals in check by dominating food and resources, with <\/span><\/div>\n
early mammals thought to be limited to small, insect-eating creatures. But recent fossil finds have called the idea into <\/span><\/div>\n
question, suggesting that they had a wider range of shapes and sizes than previously thought.<\/span><\/div>\n
Now scientists have shed further light on the matter, suggesting that early therian mammals – the predecessors of <\/span><\/div>\n
today’s placental and marsupial mammals – had developed a wide range of diets and ecological roles about 10 to 20 <\/span><\/div>\n
million years before the dinosaurs were wiped out.<\/span><\/div>\n
“It suggests that the mammal story might not be as dependent on the dinosaurs as was thought,” said David Grossnickle, <\/span><\/div>\n
a PhD student at the University of Chicago, a co-author of the study. “Even if the mass extinction hadn’t occurred, maybe <\/span><\/div>\n
mammals would have continued to diversify into some of the forms we have today.”<\/span><\/div>\n
Writing in Proceedings of the Royal Society B, researchers at the University of Chicago and the University of <\/span><\/div>\n
Southampton reveal how they turned to museum collections to scrutinise the molars of therian mammals.<\/span><\/div>\n
The scientists found that the teeth showed a variety of shapes, suggesting that the mammals had a range of diets and an <\/span><\/div>\n
assortment of ecological roles. “The great thing about molars is they are reflective of diet. Sharp, blade-like molars are <\/span><\/div>\n
going to indicate carnivory – meat-eating diets – whereas broad, flat molars are more indicative of plant-eating diets,” <\/span><\/div>\n
said Grossnickle. “The early therians were probably insect-eating small creatures like small rodents or shrews, but right <\/span><\/div>\n
before the [mass extinction] there is definitely evidence that there are some plant-eating therian mammals and some <\/span><\/div>\n
more carnivorous therian mammals.”<\/span><\/div>\n
The authors believe this increase in diversity could be linked to large evolutionary changes among flowering plants that <\/span><\/div>\n
took place during a similar period – a suggestion that has previously been proposed to explain the increase in diversity <\/span><\/div>\n
among another group of rodent-like mammals known as multituberculates that also occurred during this period.<\/span><\/div>\n
“The increase in flowering plants likely increases the number of available seeds and fruits – also insects might be co-<\/span><\/div>\n
evolving with the plants,” said Grossnickle. “So you have more seeds, fruits and insects that the animals could have <\/span><\/div>\n
eaten.” But, he adds, the idea is only a suggestion at present. “It is very speculative,” he says.<\/span><\/div>\n
While therian mammals survived the mass extinction 66 million years ago that wiped out dinosaurs, with the exception of <\/span><\/div>\n
birds, the findings reveal that their diversity was affected. That, the authors say, appears to be down to the extinction of <\/span><\/div>\n
mammals that had highly specialised diets. “Things that seem happy eating more or less anything – we see more of <\/span><\/div>\n
those after the [mass extinction] than before,” said Grossnickle. “That tells us that maybe it was better to be generalised <\/span><\/div>\n
in terms of surviving the mass extinction event.”<\/span><\/div>\n
Grossnickle believes the new research could also tie in with the much-debated suggestion that dinosaurs were in decline <\/span><\/div>\n
long before the asteroid struck, triggering the mass extinction. “If you believe that dinosaurs were on the decline, maybe <\/span><\/div>\n
in part because of environmental or climate changes, then you might also predict that mammals should have been on the <\/span><\/div>\n
decline,” he said.<\/span><\/div>\n
“On the other hand, you could also predict that mammals would have taken advantage and started to diversity as <\/span><\/div>\n
dinosaurs vacated different environments or niches. This would be in line with our results.”<\/span><\/div>\n
Others are more sceptical. “Dinosaurs by and large are pretty massive. Mammals in the interval preceding the extinction <\/span><\/div>\n
are much smaller in comparison, and it is hard to imagine that they had ecologies broadly equivalent to the dinosaurs <\/span><\/div>\n
they lived alongside,” said Matt Friedman, a palaeobiologist from the University of Oxford.<\/span><\/div>\n
But Friedman agrees that the new research contributes to a changing view of early mammals. “We do have this <\/span><\/div>\n
stereotypical view of mammals in the Mesozoic under the foot of dinosaurs, which from the perspective of size they <\/span><\/div>\n
were,” he said. “But those small mammals actually occupied a surprising number of ecological roles. I think this adds to <\/span><\/div>\n
that growing picture.”<\/span><\/div>\n
Source: the guardian<\/span><\/div>\n
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Mammals experienced a boom in diversity long before the dinosaurs became extinct 66 million years ago, overturning  the notion that their evolution was curbed by the success of the land-based reptiles, scientists have said. It has long been thought that … <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[121],"tags":[],"class_list":["post-19211","post","type-post","status-publish","format-standard","hentry","category-latest-news-en"],"_links":{"self":[{"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/posts\/19211","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/comments?post=19211"}],"version-history":[{"count":1,"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/posts\/19211\/revisions"}],"predecessor-version":[{"id":20294,"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/posts\/19211\/revisions\/20294"}],"wp:attachment":[{"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/media?parent=19211"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/categories?post=19211"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kus.edu.iq\/old\/wp-json\/wp\/v2\/tags?post=19211"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}