Scientists say they have confirmed that strange-looking fossils from more than 500 million years ago are remains of an animal.
That would make it one of the earliest known creatures.
The fossils are found within rocks. They are round with many lines, and look similar to the markings of a leaf.
The fossils were first described in 1947. They have been found in Australia and Russia. Some are very small; others are over a meter long.
Scientists have named the mysterious ancient organism that left these fossils behind Dickinsonia.
But what exactly was it?
In the past, some scientists suggested it was an animal. Others believed it was a single-celled organism called a protist.
Researchers presented evidence that Dickinsonia was an animal in a recent paper. The paper appeared in the publication Science.
The most important evidence was that Dickinsonia fossils found in Russia contained carbon-bearing substances produced by animals.
Experts not connected to the study called that evidence strong. They also said most scientists who had studied the fossils already believed that Dickinsonia was probably an animal.
Douglas Erwin is with the Smithsonian Institution. He said he is sure the fossils are from an animal.
It is not clear when Dickinsonia lived. Some fossils are about 558 million years old, said Jochen Brocks of the Australian National University in Canberra. He was one of the researchers involved in the study.
Brocks considers Dickinsonia to be the very oldest animal that we can be sure about. He added that it is about 2 million years older than another widely accepted animal fossil.
Brocks said scientists do not know much about what Dickinsonia looked like. But he said they do know it was soft and flexible.
Dickinsonia was not the first animal on Earth. Analysis of the genetic materials of living animals suggests that animals first appeared more than 720 million years ago. But scientists have never found fossils that old.
I'm Susan Shand.
1. similar to 与……相似
You should end up with something similar to what I have below.
2. more than 多于，超过
That would be more than I have expected.
3. be connected to 与……有关
Business users will be connected to it to create and manage their business rules.
4. be from 来自于
This might be from others who are doing the same thing as you — friends or family, or people in your community.
首次有记载描述这些化石是在1947年。有人在澳大利亚和俄罗斯发现了这种化石 。其中，有些很小，有些却有一米多长 。
道格拉斯 欧文（Douglas Erwin）在史密森尼学会工作。他表示自己很确定这种化石来自于动物 。
目前尚不明确狄更逊水母生活在什么时期。一些化石有近5.58亿年的历史，澳大利亚堪培拉国立大学的约亨 布拉克（Jochen Brocks）如是说道 。布拉克也参与了这项研究 。
狄更逊水母并不是地球上出现的第一种动物。对活体动物遗传物质的分析表明，动物首次出现是在7.2亿多年前 。但科学家从未发现过有7.2亿多年历史的化石 。
苏珊 尚德（Susan Shand）为您播报。