Dinosaurs may have buddied up with other species of dinosaur for safety reasons, say scientists after unexpectedly spotting tracks that suggest different kinds may have once walked side by side.
Herbivores and carnivores may once have teamed up as cross-species herds would have helped the dinosaurs fend off predator attacks and defend themselves better.
Scientists looked at dinosaur tracks dating back 76 million years that indicate mixed herds of different dinosaur species - plus predator tracks.
In an area of about 29 square metres, researchers identified tracks of at least five ceratopsids, herbivores with large horns and neck frills.
Some footprints, over 70 centimetres long, likely belong to Styracosaurus albertensis.
Other tracks, 67 centimetres long, may have been made by an armoured ankylosaur. Additional tracks may belong to a small carnivorous dinosaur and two tyrannosaurs.
Most tracks run in the same direction and are evenly distributed, suggesting the herbivores moved together as a herd across a muddy surface.
There were signs of synchrony and group behaviour among the ceratopsids, with ankylosaur tracks fitting this pattern.
The palaeontologists found three 45-centimetre tyrannosaur footprints, suggesting these predators had the herd in their sights.
However, it remains uncertain if they crossed paths with the herd. The discovery sheds light on dinosaur social behaviour, though it's unclear if herd structures were seasonal.
In total, palaeontologists discovered more than 100 well-preserved dinosaur footprints from at least four different species in Dinosaur Provincial Park, Alberta, including those of horned herbivores and large carnivorous tyrannosaurs.
The tracks, found in the rugged Badlands known for their fossil wealth, are notable for their spatial arrangement, with herbivore tracks unusually close together.
The footprints were unexpectedly found last year. It was a surprise discovery as the area's steep slopes and high erosion rates rarely preserve flat sediment surfaces needed for track formation, says Phil Bell and the University of New England in Australia team whose study was published in journal PLOS One. – dpa
