Dinosaurs survived 2 mass extinctions and 50 million years before taking over the world and dominating ecosystems
Reporting in Biology Letters, Steve Brusatte, Professor Michael Benton, and colleagues at the University of Bristol show that dinosaurs did not proliferate immediately after they originated, but that their rise was a slow and complicated event, and driven by two mass extinctions.
"The sheer size of dinosaurs like Tyrannosaurus makes us think there was something special about these animals that preordained them for success right from the beginning," Brusatte said. "However, our research shows that the rise of dinosaurs was a prolonged and complicated process. It isn't clear from the data that they would go on to dominate the world until at least 30 million years after they originated."
Importantly, the new research also shows that dinosaurs evolved into all their classic lifestyles - big predators, long-necked herbivores, etc. - long before they became abundant or diversified into the many different species we know today.
Brusatte added: "It just wasn't a case of dinosaurs exploding onto the scene because of a special adaptation. Rather, they had to wait their turn and evolved in fits and starts before finally dominating their world."
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Fishy future written in the genes
The roadmap to the future of the gorgeously-decorated fish which throng Australia's coral reefs and help earn the nation $5 billion a year from tourism may well be written in their genes.
Of particular importance may be to protect 'pioneer' fish populations which are able to re-colonise regions of reef devastated by global warming and other impacts or settle new areas as the corals move south, says Dr Line Bay of the ARC Centre of Excellence in Coral Reef Studies, James Cook University (JCU) and Australian Institute of Marine Science (AIMS).
Dr Bay and her colleagues Dr Julian Caley of AIMS and Prof Ross Crozier of the School of Marine and Tropical Biology, JCU have been studying the relationships among fishes across the Great Barrier Reef using genetic means to establish which populations are long-established and which seem to come and go in a pattern of local extinction and re-colonisation.
By studying the mitochondrial DNA of spiny damselfish collected from 15 reefs along 3 transects (lines) across the north, middle and south of the GBR, the researchers have been able to build up a 'history' of the damselfish's population.
"It's really interesting. We found, for example, that populations at the southern end of the Great Barrier Reef are 'younger' than those in the central or northern parts and have experienced larger population fluctuations. This suggests they undergo cycles of local extinction and re-settlement, which are nothing to do with human activity - whereas the central and northern populations are far more stable."