Word: acanthostega
(lookup in dictionary)
(lookup stats)
Dates: all
Sort By: most recent first
(reverse)
...amphibians, reptiles, dinosaurs, birds and mammals. Indeed, Tiktaalik roseae, the official name bestowed on the fishapod (in the language of the local Inuit, tiktaalik means "large fish in stream"), falls anatomically between the lobe-finned fish Panderichthys, found in Latvia in the 1920s, and primitive tetrapods like Acanthostega, whose full fossil was recovered in Greenland not quite two decades...
Together, these fossils have overturned the old picture of the fish-tetrapod transition, which conjured up the image of creatures like the modern lungfish crawling out of water onto land. That picture certainly didn't fit Acanthostega, whose short, flimsy legs were ill equipped for terrestrial locomotion. Rather, according to University of Cambridge paleontologist Jennifer Clack, Acanthostega was an aquatic creature that used its limbs and lungs to make a living in water. And that scenario makes sense because it sets up conditions for natural selection--the force that powers evolution--to favor transitional life-forms like the fishapod, with...
There's one problem with this familiar version of how our distant ancestors emerged from the sea: it's probably wrong. For one thing, newly assembled fossils -- in particular, a 360 million-year-old salamander-like aquatic animal called Acanthostega -- strongly suggest that toes and feet were developed before life climbed onto land, not after. Moreover, in shape and function, Acanthostega's fully jointed toes bear no resemblance to the spiky, fanlike fins of a fish. Scientists believe they understand how a fish's gills evolved into an amphibian's lungs. But how did fins turn into feet like these...
What would a fish with feet look like? It could easily resemble the Acanthostega. Mineralized bones of this strange creature, unearthed in Greenland in 1987, tend to confirm the notion that fish did not crawl onto shores on their fins, says paleontologist Michael Coates of University College, London. Instead they probably developed limbs and feet that they used in the water for millions of years before they were capable of colonizing the land...