Welcome to DU!
The truly grassroots left-of-center political community where regular people, not algorithms, drive the discussions and set the standards.
Join the community:
Create a free account
Support DU (and get rid of ads!):
Become a Star Member
Latest Breaking News
General Discussion
The DU Lounge
All Forums
Issue Forums
Culture Forums
Alliance Forums
Region Forums
Support Forums
Help & Search
Science
Related: About this forumMammals began their takeover long before the death of the dinosaurs
It's a familiar storythe mighty dinosaurs dominated their prehistoric environment, while tiny mammals took a backseat, until the dinosaurs (besides birds) went extinct 66 million years ago, allowing mammals to shine. Just one problemit's not true. A new article in the Proceedings of the Royal Society B reports that mammals actually began their massive diversification ten to twenty million years before the extinction that ended the age of the dinosaurs.
"The traditional view is that mammals were suppressed by the dinosaurs' success, and that they didn't really take off until after the dinosaurs went extinct. This study shows that therian mammals, the ancestors of most modern mammals, were already diversifying before the dinosaurs died out," says lead author David Grossnickle, a Field Museum Fellow and PhD candidate at the University of Chicago.
The old hypothesis hinged upon the fact that many of the early mammal fossils that had been found were from small, insect-eating animalsthere didn't seem to be much in the way of diversity. But over the years, more and more early mammals have been found, including some hoofed animal predecessors the size of dogs. The animals' teeth were varied, too. Grossnickle, along with his co-author Elis Newham at the University of Southampton, analyzed the molars of hundreds of early mammal specimens in museum fossil collections. They found that the mammals that lived during the years leading up to the dinosaurs' demise had widely varied tooth shapes, meaning that they had widely varied diets. These different diets proved key to an unexpected finding regarding mammal species going extinct along with the dinosaurs.
Not only did mammals begin diversifying earlier than previously expected, but the mass extinction wasn't the perfect opportunity for mammal evolution that it's traditionally been painted as. Early mammals were hit by a selective extinction at the same time the dinosaurs died outgeneralists that could live off of a wide variety of foods seemed more apt to survive, but many mammals with specialized diets went extinct.
Read more at: http://phys.org/news/2016-06-mammals-began-takeover-death-dinosaurs.html#jCp
"The traditional view is that mammals were suppressed by the dinosaurs' success, and that they didn't really take off until after the dinosaurs went extinct. This study shows that therian mammals, the ancestors of most modern mammals, were already diversifying before the dinosaurs died out," says lead author David Grossnickle, a Field Museum Fellow and PhD candidate at the University of Chicago.
The old hypothesis hinged upon the fact that many of the early mammal fossils that had been found were from small, insect-eating animalsthere didn't seem to be much in the way of diversity. But over the years, more and more early mammals have been found, including some hoofed animal predecessors the size of dogs. The animals' teeth were varied, too. Grossnickle, along with his co-author Elis Newham at the University of Southampton, analyzed the molars of hundreds of early mammal specimens in museum fossil collections. They found that the mammals that lived during the years leading up to the dinosaurs' demise had widely varied tooth shapes, meaning that they had widely varied diets. These different diets proved key to an unexpected finding regarding mammal species going extinct along with the dinosaurs.
Not only did mammals begin diversifying earlier than previously expected, but the mass extinction wasn't the perfect opportunity for mammal evolution that it's traditionally been painted as. Early mammals were hit by a selective extinction at the same time the dinosaurs died outgeneralists that could live off of a wide variety of foods seemed more apt to survive, but many mammals with specialized diets went extinct.
Read more at: http://phys.org/news/2016-06-mammals-began-takeover-death-dinosaurs.html#jCp
Therian mammals experience an ecomorphological radiation during the Late Cretaceous and selective extinction at the KPg boundary
It is often postulated that mammalian diversity was suppressed during the Mesozoic Era and increased rapidly after the CretaceousPalaeogene (KPg) extinction event. We test this hypothesis by examining macroevolutionary patterns in early therian mammals, the group that gave rise to modern placentals and marsupials. We assess morphological disparity and dietary trends using morphometric analyses of lower molars, and we evaluate generic level taxonomic diversity patterns using techniques that account for sampling biases. In contrast with the suppression hypothesis, our results suggest that an ecomorphological diversification of therians began 1020 Myr prior to the KPg extinction event, led by disparate metatherians and Eurasian faunas. This diversification is concurrent with ecomorphological radiations of multituberculate mammals and flowering plants, suggesting that mammals as a whole benefitted from the ecological rise of angiosperms. In further contrast with the suppression hypothesis, therian disparity decreased immediately after the KPg boundary, probably due to selective extinction against ecological specialists and metatherians. However, taxonomic diversity trends appear to have been decoupled from disparity patterns, remaining low in the Cretaceous and substantially increasing immediately after the KPg extinction event. The conflicting diversity and disparity patterns suggest that earliest Palaeocene extinction survivors, especially eutherian dietary generalists, underwent rapid taxonomic diversification without considerable morphological diversification.
http://rspb.royalsocietypublishing.org/content/283/1832/20160256
It is often postulated that mammalian diversity was suppressed during the Mesozoic Era and increased rapidly after the CretaceousPalaeogene (KPg) extinction event. We test this hypothesis by examining macroevolutionary patterns in early therian mammals, the group that gave rise to modern placentals and marsupials. We assess morphological disparity and dietary trends using morphometric analyses of lower molars, and we evaluate generic level taxonomic diversity patterns using techniques that account for sampling biases. In contrast with the suppression hypothesis, our results suggest that an ecomorphological diversification of therians began 1020 Myr prior to the KPg extinction event, led by disparate metatherians and Eurasian faunas. This diversification is concurrent with ecomorphological radiations of multituberculate mammals and flowering plants, suggesting that mammals as a whole benefitted from the ecological rise of angiosperms. In further contrast with the suppression hypothesis, therian disparity decreased immediately after the KPg boundary, probably due to selective extinction against ecological specialists and metatherians. However, taxonomic diversity trends appear to have been decoupled from disparity patterns, remaining low in the Cretaceous and substantially increasing immediately after the KPg extinction event. The conflicting diversity and disparity patterns suggest that earliest Palaeocene extinction survivors, especially eutherian dietary generalists, underwent rapid taxonomic diversification without considerable morphological diversification.
http://rspb.royalsocietypublishing.org/content/283/1832/20160256
InfoView thread info, including edit history
TrashPut this thread in your Trash Can (My DU » Trash Can)
BookmarkAdd this thread to your Bookmarks (My DU » Bookmarks)
0 replies, 729 views
ShareGet links to this post and/or share on social media
AlertAlert this post for a rule violation
PowersThere are no powers you can use on this post
EditCannot edit other people's posts
ReplyReply to this post
EditCannot edit other people's posts
Rec (8)
ReplyReply to this post