Where the wild giants lived
19 April 2010, by Sara Coelho
Scientists have found that some giant sauropod dinosaurs preferred to live in inland habitats, while others were more common in coastal areas. The findings come from a ground-breaking study in dinosaur ecology and shed a new light on sauropod evolution.
A herd of Alamosaurus, a titanosaur species that lived in the Late Cretaceous
Sauropods were gigantic herbivores that first appeared about 220 million years ago, at the beginning of the age of the dinosaurs. The group quickly diversified into many sub-types and species.
Dinosaur enthusiasts will have no trouble recognising them – their huge size, lengthy tail and long neck ending in a tiny head are unmistakable. But little is known about the ecological preferences of the sauropod groups and how this has affected their evolution.
To figure out if sauropod groups lived in different habitats, palaeontologists Dr Philip Mannion and Dr Paul Upchurch, based at University College London, focused on titanosaurs, a key group to understand sauropod evolution.
Titanosaurs were one of the last sauropod groups to appear in the geological record 160 million years ago and the only ones left by the time all the dinosaurs disappeared in a mass extinction. 'Some titanosaurs had armour, some were very large and they had different teeth to most other sauropods,' says Mannion.
Mannion compiled a 2500-entry database with all known occurrences of sauropod fossils worldwide. He then classified the fossils as titanosaurs or non-titanosaurs and noted the type of environment where the animals lived. This is possible thanks to the different geological properties of the rocks where the fossils were found.
The database also includes all known sauropod tracks. It's easy to tell which ones were made by titanosaurs because they had a distinct hip structure, with a wider stance and left footprint trails different from other sauropods.
By comparing the groups with the environment where the animals lived, Mannion found that 'titanosaurs preferred inland habitats, for example lake and river environments or mountainous areas with irregular terrain.' On the other hand, non-titanosaur sauropods preferred to live in coastal areas.
'This may explain why titanosaurs survived for 20 million years, after all other sauropods went extinct,' says Mannion, who published the findings in Paleobiology. 'Maybe their preference for inland environments was beneficial and protected the group from extinction until they disappeared with all other dinosaurs.'
The titanosaurs were also better adapted for life in mountainous areas: 'their wider stance perhaps benefits walking in irregular terrain,' he explains.
This was the first large-scale, detailed study of the ecological preferences of any dinosaur group. We may know what they looked like thanks to their bones and what they had for dinner from their teeth, but where exactly they lived proves more difficult, mostly because of lack of data to make significant statistical analysis.
Philip D. Mannion and Paul Upchurch. A quantitative analysis of environmental associations in sauropod dinosaurs. Paleobiology, 36(2), 2010, pp. 253-282
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