In addition to fossils, fossilized footprints can reveal a lot about the prehistoric world. In South Australia, researchers have now discovered some of the oldest bird tracks known to date in this part of the world. Such finds have been rare until now on the southern continents that emerged from the Gondwana landmass. The footprints now discovered are at least 120 million years old and indicate that different species of birds were already inhabiting the area at that time – perhaps as a seasonal stop on their migration.
In the Northern Hemisphere, fossil evidence of birds dates back to the Upper Jurassic, more than 150 million years ago. On the other hand, for the southern continents, which once emerged from the original Gondwana land mass, it is unclear how and when birds spread there. The oldest known fossils in the form of a bird bone and feather come from the Wonthaggi Formation in Victoria, Australia and are estimated to be about 120 million years old.
“Given the scarcity of Mesozoic bird fossils, we have little evidence about when birds originated in Australia and most other Gondwana lands, let alone how they interacted with their environment,” wrote a team led by Anthony Martin of Emory University in Atlanta, Georgia. . But during excavations between 2020 and 2022, co-author Melissa Lowry of Monash University in Victoria discovered additional evidence of Cretaceous birds. In the Wonthaggi Formation, from which the oldest bird body fossils to date also come, she found several fossilized footprints that appear to have been left by various bird species more than 120 million years ago.
Further investigations by the team revealed the presence of 27 footprints. “The identity of these tracks as bird tracks is confirmed by their three-toed shape, thin toes in relation to the length of the track, wide spread angles, and sharp claws,” the researchers explain. Because individual tracks have dramatically different shapes and sizes, Martin and his team hypothesize that they were made by several different bird species. Some of these are among the largest known from the Early Cretaceous.
Prehistoric migratory birds?
“Despite the lack of connected tracks, the close spacing and similar orientation of the tracks on some layered surfaces suggests social coexistence,” the team wrote. At the time the bird tracks came, the area experienced regular seasonal floods. “Because we detected bird tracks in several stratigraphic layers of the Wunthaggi Formation, we concluded that birds visited the area frequently,” De Martin and colleagues explain. “The tracks were likely created seasonally during the polar summer, which may also indicate the early migration of these birds.”
The trails provide insight into the early history, biodiversity and adaptation of birds in Gondwana. Although there are no similar ancient monuments known from other parts of former Gondwana, paleontologists assume that the presence of birds at that time was not limited only to the area around the Wonthaggi Formation. “We hope that our discovery of trace fossils will inspire other researchers to search for and find additional tracks of Early Cretaceous birds in other regions of the Southern Hemisphere,” the team said.
Source: Anthony Martin (Emory University, Atlanta, GA, USA) et al., PLoS ONE, doi: 10.1371/journal.pone.0293308
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