Four-legged Creature's Footprints Force Evolution Rethink
By Jeanna Bryner, Managing Editor
posted: 06 January 2010 01:00 pm ET
Four-legged creatures were mucking around a muddy basin in what is now Poland about 397 million years ago. And they left behind distinctive footprints, which have turned back the clock on the evolution of these landlubbers.
Scientists discovered the fossilized prints, which included various trackways and isolated prints, in the Holy Cross Mountains in southeastern Poland.Â Analyses suggest most if not all of them came from different tetrapod species â€” which are four-legged animals that had backbones, such as amphibians â€” with some possibly belonging to juveniles and adults of the same species.
The land creatures likely had bodies shaped somewhat like crocodiles, with fin-like tails and stumpy legs. And some of them were pretty big, reaching up to about 10 feet (3 meters) in length, the researchers said.
Limestone slab from Poland with fossil footprints.
Laser scan of surface showing detail of individual print and diagram relating it to an animalâ€™s foot.
Some quotes:For references
Of course a 'refining' of the theory has to come now. But the nice little story of taktaalik coming out of the sea is over--these creatures were crocodile-like, and of different species--IN THE MOUNTAINS. Oh yes! It was tectonic uplift!
*Â â€œThey force a radical reassessment of the timing, ecology and environmental setting of the fish-tetrapod transition, as well as the completeness of the body fossil record.â€5
Â Â * â€œ[It] will cause a significant reappraisal of our understanding of tetrapod origins.â€6
Â Â * â€œ[They] could lead to significant shifts in our knowledge of the timing and ecological setting of early tetrapod evolution.â€7
Â Â * â€œWe thought weâ€™d pinned down the origin of limbed tetrapods. We have to rethink the whole thing.â€8
Â Â * â€œThatâ€™s surprising, but this is what the fossil evidence tells us.â€9
Â Â * â€œThese results force us to reconsider our whole picture of the transition from fish to land animals.â€10
The article failed to mention the tracks are in limestone. My first thoughts are HOW did tracks left in soft diatomic or calcite material dry out and preserve for 397 million years???
How about a crocodile on wet leftovers of a diatomic and/or planktonic bloom (depending on the purity of the limestone) in the receding waters of the deluge? Sounds like a plausible explanation.
Any thoughts? Do you think textbooks and museum presentations will be changed? Did anyone see this on CNN? Maybe I missed it. Does anyone know how they dated it? It doesn't say.