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Re: Mesozoic multituberculates diversified well before dinosaur extinction



Very interesting!! This shows the likely size increase of multis...any
evidence of similar trends in other mammals? I think Cimolestes and
Zhelestids increased similarly, some of them anyway. If so, could be
relaxation of dinosaur-enforced size restriction, or opening of new
niches afforded by floral revolution.
Thanks, John Bois

On Wed, Mar 14, 2012 at 2:36 PM, Ben Creisler <bcreisler@gmail.com> wrote:
> From: Ben Creisler
> bcreisler@gmail.com
>
> OK--again, not dinos as such. However, this research suggests that
> dinosaurs did not hold back mammalian evolution as much as sometimes
> claimed.
>
>
> Gregory P. Wilson, Alistair R. Evans, Ian J. Corfe, Peter D. Smits,
> Mikael Fortelius & Jukka Jernvall (2012)
> Adaptive radiation of multituberculate mammals before the extinction
> of dinosaurs.
> Nature (advance online publication)
> doi:10.1038/nature10880
> http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10880.html
>
>
> The Cretaceous–Paleogene mass extinction approximately 66 million
> years ago is conventionally thought to have been a turning point in
> mammalian evolution. Prior to that event and for the first two-thirds
> of their evolutionary history, mammals were mostly confined to roles
> as generalized, small-bodied, nocturnal insectivores, presumably under
> selection pressures from dinosaurs. Release from these pressures, by
> extinction of non-avian dinosaurs at the Cretaceous–Paleogene
> boundary, triggered ecological diversification of mammals. Although
> recent individual fossil discoveries have shown that some mammalian
> lineages diversified ecologically during the Mesozoic era,
> comprehensive ecological analyses of mammalian groups crossing the
> Cretaceous–Paleogene boundary are lacking. Such analyses are needed
> because diversification analyses of living taxa allow only indirect
> inferences of past ecosystems. Here we show that in arguably the most
> evolutionarily successful clade of Mesozoic mammals, the
> Multituberculata, an adaptive radiation began at least 20 million
> years before the extinction of non-avian dinosaurs and continued
> across the Cretaceous–Paleogene boundary. Disparity in dental
> complexity, which relates to the range of diets, rose sharply in step
> with generic richness and disparity in body size. Moreover, maximum
> dental complexity and body size demonstrate an adaptive shift towards
> increased herbivory. This dietary expansion tracked the ecological
> rise of angiosperms and suggests that the resources that were
> available to multituberculates were relatively unaffected by the
> Cretaceous–Paleogene mass extinction. Taken together, our results
> indicate that mammals were able to take advantage of new ecological
> opportunities in the Mesozoic and that at least some of these
> opportunities persisted through the Cretaceous–Paleogene mass
> extinction. Similar broad-scale ecomorphological inventories of other
> radiations may help to constrain the possible causes of mass
> extinctions.
>
> New articles:
>
> http://news.sciencemag.org/sciencenow/2012/03/dino-deaths-be-damned.html?ref=hp
>
> http://www.eurekalert.org/pub_releases/2012-03/uow-smu031112.php