Oldest footprints found (in Nevada)

[Astronuc]

and accidentally

Oldest 'Footprints' on Earth Found
http://news.yahoo.com/s/livescience/oldestfootprintsonearthfound

The oldest-known tracks of a creature apparently using legs have been discovered in rock dated to 570 million years ago in what was once a shallow sea in Nevada.

Scientists think land beasts evolved from ancient creatures that left the sea and evolved lungs and legs. If the new finding is real - the discoverer says will fuel skepticism - it pushes the advent of walking back 30 million years earlier than any previous solid finding.

The aquatic creature left its "footprints" as two parallel rows of small dots, each about 2 millimeters in diameter. Scientists said today that the animal must have stepped lightly onto the soft marine sediment, because its legs only pressed shallow pinpoints into that long-ago sea bed.
. . . .

Much of the N. American continent was underwater during the distant past.

 

[B. Elliott]

Good find Astronuc. That's very odd because if the estimated time is correct, that places it well before the Cambrian explosion also well before known complex life forms evolved. A world thought to only be dominated by worms, echinoderms, and other soft-shelled organisms.

Even though this picture is ~60Ma years later, it gives you a good idea of the amount of ocean occupying future land of North America.
http://www.winona.edu/geology/MRW/mrwimages/Cambrian510.jpg

Here's one at ~545 - 535Ma
http://jan.ucc.nau.edu/~rcb7/550NAt.jpg

 

[LURCH]

Since these footprints were found in rock that used to be the bottom of a shallow sea, wouldn't it be more natural to conclude that they were made by some aquatic creature with "stumps" for walking along the bottom (like an early precursor of the coelacanth), rather than a land beast or amphybian?

It would seem to me that, rather than pushing back the advent of land walking creatures by 30 million years, this discovery (if verified) would indicate that the evolution of legs was not "purpose made" for walking on land. Instead, it would appear that these "stumps" evolved for the purpose of walking along the sea floor, and then were later adapted for short walks across obstacles between bodies of water.

 

[matthyaouw]

Erm, that is what they concluded.

The aquatic creature left its "footprints" as two parallel rows of small dots, each about 2 millimeters in diameter. Scientists said today that the animal must have stepped lightly onto the soft marine sediment, because its legs only pressed shallow pinpoints into that long-ago sea bed.

Interestung stuff