Paleontologists have discovered 27 bird footprints and other traces — dated to between 120 and 128 million years ago (Early Cretaceous epoch) — in the Wonthaggi Formation of Victoria, Australia. The discovery opens another window onto early bird evolution and possible migratory behavior and confirms the earliest known presence of birds in Australia and the rest of the supercontinent Gondwana.
Cretaceous bird fossils are abundant and diverse in northern continents, but extremely rare in southern regions that were once part of the Gondwana supercontinent.
This presents a challenge for paleontologists trying to understand the distribution of early birds.
“Most of the bird tracks and body fossils dating as far back as the Early Cretaceous are from the northern hemisphere, particularly from Asia,” said Emory University Professor Anthony Martin, first author of the study.
“Our discovery shows that there were many birds, and a variety of them, near the south pole about 125 million years ago.”
In their study, Professor Martin and his colleagues examined a series of bird footprints from the Early Cretaceous Wonthaggi Formation, south of Melbourne, Victoria, Australia.
The 27 footprints vary in form and size and indicate the presence of several different types of birds.
They are from 7 to 14 cm wide — which is similar to tracks of modern-day shorebirds, such as small herons and oystercatchers — and are among the largest known from the Early Cretaceous.
The footprints are present in multiple stratigraphic layers of an ancient polar floodplain, suggesting that these birds might have visited this area seasonally, perhaps as part of a migratory route.
“The birds would likely have been stepping on soft sand or mud,” Professor Martin said.
“Then the tracks may have been buried by a gentle river flow that deposited more sand or mud on top of them.”
Other than one bone and a few feathers, these footprints represent the oldest known evidence of birds…
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