- Victoria Gil
- BBC science reporter
Scientists say they have solved an evolutionary puzzle related to a 500-million-year-old spiny, microscopic creature with a mouth but no anus.
When it was discovered in 2017, this small, sack-shaped fossil of a marine animal was said to be the oldest known ancestor of humans.
Saccorhyntys crownarius, as this ancestral organism is known, is tentatively classified within the group of deuterostomes, characterized by The anus forms in front of his mouth during fetal development.
These are the primitive ancestors of vertebrates, including humans.
Now, a new study suggests that Saccorhytus should be classified into an entirely different group of animals.
A team of researchers in China and the UK conducted a very detailed X-ray analysis of the creature and came to the conclusion Belongs to a group called ecdysozoaThey are the ancestors of spiders and insects.
One of the origins of this evolutionary confusion was the animal’s lack of an anus.
Emily Carlisle, a researcher who has studied Saccorhytus in detail, told about the topic on BBC Radio 4.It’s little worrying, (the majority) Many ecdysozoans have an anus, so why shouldn’t this be one?
An “interesting option” to explain this, he said, is that ancestor even before this entire group did not have an anus, and that Saccorhytus had evolved after that.
“It could have been lost as he was developing, maybe he didn’t need it or he could just sit in one place with one hole for everything,” he said.
However, the main reason for the “repositioning” of Saccorhytus in the Cambrian tree of life – a division of the geological time-scale that belongs to the Paleozoic era – is that upon initial examination, The foramina surrounding the mouth has been interpreted as the pores of the gills, a primitive feature of bivalves.
When the scientists looked in more detail, using powerful X-rays to closely examine the 1-mm-diameter creature, they realized it was actually the base of its spine that had separated.
Scientists who study these fossils try to put each animal on the tree of life, much like a family tree, something that allows them to build the big picture to understand it. Where did they come from and how did it evolveRon.
“Sacorhytus would have lived in the oceans, in sediments with its spines in place,” explained Carlisle, who works at the University of Bristol in the United Kingdom.
“We believe he sat there (where he was found),” In a very exotic environment with many animals It will look like some living creatures on the outside, but a lot of completely alien ones.”
The rocks containing these Cambrian fossils are still being studied.
“There is still a lot to learn about its environment,” Carlisle added.
“The more I study paleontology, the more I realize how missing it is. In terms of this creature and the world it lives in, we’re really just scratching the surface.”
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