Friday Headlines, January 17, 2014
THE LATEST IN THE GEOSCIENCES
Tiktaalik was four-wheel-drive
Well, this one news story is worth it’s own blog post. It’s been bouncing around the interwebs these past few days. I’ll give you three different web articles to read:
See, Tiktaalik is this fossil animal that could as easily be called an amphibian as it is called a fish. I wrote something about it many years ago, explaining how it is a great example of a transitional form between fish and amphibians. You can read that here.
The end conclusion was that Tiktaalik would best be called a fish, because it was probably swimming more than anything, although it does lack gill covers characteristic of fish.
At the time, however, only the front limbs of Tiktaalik were known. These were remarkable, because they were essentially amphibian limbs. They only lacked the main hand bones (metacarpals and phalanges), and instead had fin rays. All the other bones were there: the humerus (upper arm), the radius and ulna (lower arm), and some of the carpal (wrist) bones are there.
But the hind limb had not been found. Thus, Tiktaalik was often portrayed propping itself up on its forelimbs and dragging its back end behind.
But now, researchers have found the hind limbs. And what they found was not drag-behind legs, but a good solid hip joint connected to the vertebral column – meaning that the back legs were also used for propulsion.
Tiktaalik could get around on all four limbs. It didn’t drag itself through the mud, at least not a whole lot more than a modern salamander might.
Tiktaalik is an interesting mosaic of clearly fish-like features and clearly amphibian like features. It continues to be classified as a fish, but classification is such an arbitrary thing.