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Mesozoic multituberculates diversified well before dinosaur extinction

From: Ben Creisler

OK--again, not dinos as such. However, this research suggests that
dinosaurs did not hold back mammalian evolution as much as sometimes

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)

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

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