Triops Longicaudatus
Triops Longicaudatus Red
Triops Longicaudatus
Triops Longicaudatus Red
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Palaeontology: Bird tracks from the Cretaceous period discovered in the southern hemisphere
Modern avifauna has its roots in a side branch of the dinosaur family tree, a fact that most palaeontologists have no doubt about. Their closest living relatives are the crocodiles, and it is thought that their direct ancestors were probably arboreal, small predatory dinosaurs from the Maniraptora group. The date of the appearance of the first creatures that can already be considered birds is the subject of controversial debate.
Birds apparently already inhabited the southern polar regions 120 million years ago
The oldest known fossils that can be considered bird remains come from Upper Jurassic deposits that are around 150 million years old. Particularly noteworthy are specimens from the Tiaojishan Formation in China, which have been dated to an age of up to 160 million years.
It probably took some time for representatives of this new evolutionary branch to reach the southern hemisphere of our planet. There are very few early bird fossils from the southern continents that were once part of the land of Gondwana. Therefore, the picture of the distribution of the first birds remains extremely incomplete.
However, researchers have now discovered actual traces that indicate that birds inhabited the southern polar regions 120 million years ago: A team led by Anthony Martin from Emory University (USA) reports in the scientific journal Plos One on the discovery of a series of bird footprints in the Early Cretaceous Wonthaggi Formation in Victoria, Australia.
The palaeontologists described 27 individual tracks that could have been made exclusively by birds. These are between seven and 14 centimetres wide and resemble the footprints of modern-day shorebirds. The different sizes and shapes of the prints even indicate the presence of different bird species, some of which could be among the largest species that existed during the Cretaceous period.
Apart from a few fossilised bones and feathers, these are the oldest known evidence of birds in Australia or other parts of former Gondwana. Furthermore, the tracks represent the earliest evidence that birds also colonised the regions near the poles. However, it remains to be seen whether these bird tracks are merely random isolated cases or evidence of a denser bird population in Gondwana.
These footprints have been preserved in various layers of an ancient polar floodplain. This could indicate that these birds may have visited the area seasonally, possibly as part of a migration route, the researchers surmise.
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