The oldest bird footprints ever discovered in Australia suggest there were birds – big ones – soaring over the continent as long ago as the Early Cretaceous Period. How do researchers know these birds were flying, and not just walking? Science!
The prints were found embedded in a slab of sandstone among the coastal cliffs of Dinosaur Cove – a notoriously fossil-rich (and, frankly, pretty epically named) paleontological site in Victoria, Australia – and paleontologists who discovered the tracks say they were not left by a small bird. Their size and shape suggest they were made by a prehistoric species about the size of a modern-day great egret, which can weigh upwards of three pounds. What's more, a drag mark – presumably made by the bird's right, rear toe – suggests the tracks were left by a species capable of flight. The print "has a beautiful skid mark from the back toe dragging in the sand, likely caused as the bird was flapping its wings and coming in for a soft landing," said Emory University paleontologist Anthony Martin, who oversaw the analysis of the footprints, in a statement. "I immediately knew what it was – a flight landing track – because I've seen many similar tracks made by egrets and herons on the sandy beaches of Georgia."
To top it all off, the tracks were discovered beside another imprint that appears to have been made by a non-avian theropod called a coelurosaurus. The upshot? "These tracks are evidence that we had sizable, flying birds living alongside other kinds of dinosaurs on these polar, river floodplains, about 105 million years ago," said Martin.
Martin specializes in trace fossils (that is, fossilized evidence of such delicate remains as tracks, burrows and nests), which sounds like an incredibly difficult thing to specialize in. The photo above (taken by Martin) shows the hunk of sandstone that the tracks were discovered on. The photo was featured over at LiveScience, and I cannot for the life of me spot the "drag mark made by the rear toe" that its caption refers to [Ed. Note: With some helpful guidance from Aloicious, i have spotted the drag mark]. I can start to make out the print in the photo below (also by Martin), but not the one above.
In any case, Martin, trace fossil expert that he is, was certainly the perfect person to scrutinize the prints. What blows me away is that he's not the one who found them – volunteers working in Dinosaur Cove did that. All I can say is those must have been some eagle-eyed volunteers.
"The picture of early bird evolution in the Southern Hemisphere is mostly incomplete," added Martin, "but with these tracks, it just got a little better."
Martin's team's analysis will be published in the journal Paleontology.