The Winding Paths
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The surface wasn’t all it was cracked up to be for some of the primordial species that emerged from the Earth’s oceans hundreds of millions of years ago, according to Cosmos Magazine.
In 2004, paleontologists discovered the fossilized remains of Tiktaalik roseae, a 375 million-year-old creature that is generally thought to be the ancestor of terrestrial vertebrates, which also includes humans.
The fishapod – an early fish that developed limbs for walking – was not alone when it began its trek on dry land, however.
Recently, scientists found that the newly-discovered Qikiqtania wakei initially joined the Tiktaalik’s journey but later went back to its watery abode – and took a different evolutionary path.
In their study, the team reported that the Qikiqtania’s remains were initially mistaken for those of the Tiktaalik because they were both found around the same time. But further studies uncovered a number of differences between the two fishapods.
While they share many features, Qikiqtania were smaller in size and more suited for aquatic life: These had a pectoral fin with a humerus bone that lacked the muscle ridges which would otherwise suggest a limb designed for walking on land.
Although somewhat older than its famous relative, Qikiqtania shares a branch of the evolutionary tree with the first vertebrates with finger-like digits.
The findings provide more evidence that species don’t evolve in a linear fashion, the authors noted.
“Tiktaalik is often treated as a transitional animal because it’s easy to see the stepwise pattern of changes from life in the water to life on land,” said lead author Thomas Stewart. “But we know that in evolution things aren’t always so simple.”