Ever found the evolutionary leap from dinosaur to chicken a bit hard to imagine? Well, scientists have just solved one more link in that chain – and it could all come down to a prehistoric series of colossal volcanic eruptions across the planet.
The new research, from University College London (UCL) and the University of Vigo, Spain, reveals the moment that some dinosaurs developed endothermy: the ability to regulate their own body temperature and generate internal heat. This trait of being 'warm-blooded' is shared by all mammals and birds today.
Over recent years, new research has suggested that dinosaurs weren’t all the cold-blooded animals like today’s reptiles that we thought they were. The fact that some dinosaurs had feathers suggested that they might be endothermic, but when these warm-blooded dinosaurs (including the ancestors of today’s birds) appeared has not been known – until now.
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So when did it happen? The researchers think that these dinosaurs emerged about 180 million years ago in the early Jurassic period – when intense volcanic activity forced species to adapt to climate change across the planet.
Known as the Jenkyns event, lava and volcanic gasses burst through giant fissures in the Earth’s surface – leading to global warming and the extinction of plants. The researchers say that this split up the main dinosaur groups as they developed different climate preferences.
“I was surprised [by the results], particularly with the coincidence of the majority of evolutionary change at the Jenkyns event,” first author Dr Alfio Alessandro Chiarenza told BBC Science Focus.
“This is a relatively newly recognised hyperthermal (global warming) event traced in our geologic record and the fact that it might have had such an influence on global ecosystems, and also have affected the evolution of dinosaurs, is quite a new concept.”
Published in the journal Current Biology, the study analysed the spread of dinosaurs across different climates on Earth during the Mesozoic era (230-66 million years ago) through 1,000 fossils, climate models, geography, and evolutionary trees.
They discovered that two of the three main dinosaur groups moved to colder climates during the early Jurassic period, and responded to this change with endothermy. These two groups include theropods (such as T.rex and Velociraptor) and ornithischians (including relatives of Stegosaurus and Triceratops).
However, they think the third group, sauropods (the family of massive dinosaurs including Brontosaurus), stuck to warmer parts of the planet and remained cold-blooded.
Endothermy may have allowed the dinosaurs to grow faster, produce more offspring, and sustain physical activity for longer. These benefits may have helped their lineages survive through environmental degradation; despite global warming, the polar regions were still dark for about four months a year.
Meanwhile, the researchers think the sauropods thrived in arid environments – their cold-blooded bodies needing the warmth and their large sizes helping to store this warmth for longer. “The bigger your water pot is, the slower it cools down – and that’s what we think sauropods were doing,” explained Chiarenza.
The researchers think that discovering how climate impacted dinosaur evolution could shed light on how the current climate crisis is affecting species now.
“Another reason to investigate and understand better global warming events in our geologic past is to understand what effects they may have on biodiversity,” said Chiarenza. “A lesson from the deep past for our future.”
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