Thursday, April 3, 2014
It's a series of faint, but very definite circles. They are almost identical in size and they overlap quite often. And then when you go to the end of the series of discs, you find a hollow with the imprint of a very distinct fossil, that of Dickinsonia. Dickinsonia was a cushionlike creature that lay flat on the seafloor. It ranged from the size of a penny to that of a bath mat. These imprints represent something very important. They are the first evidence of a kind of mobility of Dress Up Games on the seafloor. The first animal movements were undoubtedly slow, but perhaps even too slow to notice. To see them in action, you have to speed them up. Dickinsonia crept from one feeding place to the next, absorbing the organic matter beneath it and then moving on once again. Perhaps it moved with the help of hundreds of tiny tubular feet, as starfish do today. The excavations at Ediacara reveal that Dickinsonia wasn't the only mobile creature around. Dress Up Games everywhere were on the move, actively seeking food. This shape here is a resting place of a sluglike animal called Dress Up Games. And these here, marks, are showing how it fed. It had a proboscis, a snout, and it fed by sifting through the mud, making these scratch marks. But it tells us more than how this animal fed. It also tells us how it moved because if you look back this way, this is where is started feeding and then it moved along here with more feeding marks and grooves, and then it settled down here into the mud where its final resting place was. So this shows that the animal not only fed like that, it actually moved like that. Dress Up Games was a very early ancestor of today's molluscs. It probably had a single muscular foot, just as snails and slugs have today with which it pulled itself along the sea bottom. Our speededup view of the Ediacaran seafloor gives an idea of what a busy place the oceans had now become. Whether that movement is by creeping or crawling over the seafloor, it doesn't matter because that animal has advantages over an animal that is fixed to the seafloor. It can move away from danger. It can move towards richer sources of food. It can move away from places which are overcolonised by its neighbours.
Etiketler: Barbie Dress Up