Despite two centuries of incredible discoveries, an inability to locate fossils means that many secrets about these species will never be found, says David Hone
THE study of dinosaurs has made some amazing strides in the past 20 years. The discovery of numerous fully feathered dinosaurs offers incontrovertible evidence of the evolution of birds from their non-flying ancestors, for instance. We also have fossils that preserve ancient patterns of these long-extinct animals.
Around 50 new dinosaur species have been named every year of the past two decades. New studies have appeared on dinosaur behaviour, ecology, sex, physiology, brain structure, hearing and many more features besides. It is truly a treasure trove of data, and new avenues of research keep producing ever more interesting and surprising insights into these animals. And yet, rather inevitably, the fossil record is incredibly incomplete. For all the progress that has been made in two centuries of studying dinosaurs, there are still innumerable things that we don’t know about them.
We may have some ideas about the colours of a few dinosaurs, but these are only a handful of individuals that may not even be that representative of their species, let alone any others. We have done detailed studies of how Tyrannosaurus rex could stand, walk, run and turn, but there is nothing like this even for the other 30 species of tyrannosaurs, let alone other groups. Those gaps may at least be filled with new finds one day, but what about the things we might never know?
Think about some of the strangest animals out there, those that are most unlike their near relatives or are hold-outs of some long-lost group. Giant tortoises, marine iguanas and flightless cormorants on the Galapagos Islands; kiwis, kakapo and tuatara in New Zealand; the (now sadly extinct) rails of Hawaii; lemurs and extinct elephant birds on Madagascar; and so on.
What they have in common is where they live – islands, usually ones that are both volcanic and a long way from any other land masses, and they are often tropical too. These are places where isolated populations can cling on and take interesting turns, as small groups evolve under unusual conditions. They are often free from some of the constraints that come from the presence of competitors and predators, which can allow them to flourish where elsewhere they have perished, or to diversify and produce new and unusual forms.
The thing is, though, such environments are terrible for forming fossils. Small bits of land are likely to have limited numbers of large rivers and lakes with lots of silt to bury animals. Tropical environments have very high rates of decay, so dead bodies often don’t last long enough to be buried. Volcanic islands can easily sink into the sea and be at the mercy of tectonic activities, and such places are generally very unlikely to be exposed on the surface where paleontologists can pick at them 100 million years later.
In short, however bizarre we consider dinosaurs to be now, they almost certainly produced far more interesting and unusual animals on all manner of islands in the Mesozoic Era (around 252 million to 66 million years ago), but it is incredibly unlikely that we will ever find them. Either the fossils never formed or those islands have been destroyed and are now inaccessible.
Our knowledge of the evolution of animals on islands is enough to give us confidence that strange dinosaurs appeared in these places, though similarly, our understanding of the processes of fossilisation tells us that we are unlikely to access the fossils in the future, however much we dig.
We have learned so much about dinosaurs, and there is still so much more to come. But there are fascinating gaps we might never fill, with only tantalising hints about these wondrous ancient creatures.
David Hone is the author of The Future of Dinosaurs (Hodder & Stoughton).
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