One commonly held belief is that dinosaurs became extinct before mammals began to flourish – that the events leading to the mass death of dinosaurs allowed mammals to develop fully. Now a report in the journal Nature – and an accompanying one in Science Magazine – seek to prove otherwise.
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 angiosperms8 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.
It is fairly academic stuff which some might find a bit esoteric … but I found utterly fascinating. However, you only get a small portion online – I had to head to our company’s online journal library to check out the rest. If you don’t have access to Nature or find it a bit dry, perhaps an article called “Dino Deaths Be Damned” would be a bit more enjoyable!
Here is what Science has to say:
By now, even schoolchildren know the story: Sixty-five million years ago, a giant asteroid slammed into Earth, ending the reign of the dinosaurs and allowing our mammalian ancestors to flourish. But a new study suggests that some of the earliest mammals were already doing well millions of years before dinos kicked the bucket. These mouse-sized creatures, known as multituberculates, appear to have started proliferating around the same time that flowering plants went through their own burst of evolution.
Wilson notes that the diversification of the multituberculate diet occurred during an era when flowering plants, or angiosperms, were evolving into a variety of forms, including trees, herbaceous plants, and epiphytes, a group of nonparasitic species that live on other plants and that includes today’s orchids and bromeliads. That spate of evolution among angiosperms, which occurred millions of years before the mass extinction that claimed the dinosaurs, opened new ecological opportunities that multituberculates then diversified to exploit, the researchers suggest. Not only does the new study show that multituberculates began to diversify long before the dinosaurs died out, Wilson says, it reveals that species with a plant-based diet grew larger, expanding from the size of a mouse to a body mass of about 5 kilograms (slightly heftier than a large groundhog).
It is some pretty amazing stuff that could potentially change up everything we think we know about dinosaur history … again. It is amazing to me just how much has changed in our knowledge and understanding of those eras of history just during my lifetime – I can’t wait to see what else we can learn from our ancient pre-ancestors!