In every family tree there is someone you would rather not be part of your family, and for many paleobiologists this has been the Saccorhytusan extinct microbe that looked like a talking cactus, but what made it particularly embarrassing was that its giant mouth had no counterpart in the back.
Fortunately, however, we no longer have to acknowledge this beast without anussince it is now officially someone else’s problem, in fact it has recently been discovered that we and the Saccorhytus are not relatedor at least no more than any other form of terrestrial life.
The news it is so joyful that it has been announced in Nature and comes as a result of the abundance of new specimens measuring 1 millimeter (0.04 inch) found in the Chinese province of Shaanxi.
“Some of the fossils are so perfectly preserved that they seem almost alive”
said the Professor Yunhuan Liu of Chang’an University, Xi’an. Fortunately, both for our brains and for the creatures they might plunder, Saccorhytus has been dead for 530 million years.
The history of Saccorhytus and why it was thought to be our “family member”
The reason we thought we should make room for Saccorhytus at the family reunion lay in the tiny holes around the mouths angry about the fossil specimens, these in fact, according to what paleontologists thought, they were tiny gillswho placed their owners in the deuterostomesthe clade of animals whose mouth is formed only after its anus during embryonic development.
In case you don’t know, this family includes us and all other vertebrates along with starfish and some worms. It seems like a strange place to put a creature without anus, but the gills would have been tangible proof, and although being a deuterostome it wouldn’t necessarily have made Saccorhytus our direct ancestor, but it would certainly imply a strong connectionespecially since it would have been the oldest deuterostome we could find.
However, the co-author of the PhD Emily Carlisle of the University of Bristol noted:
“Fossils can be quite difficult to interpret and Saccorhytus is no exception. We had to use a synchrotron, a type of particle accelerator, as the basis for our fossil analysis. “
The images taken with the intense X-ray light produced by the synchrotron were used to build 3D models of the fossils, and based on these, Liu, Carlisle and co-authors concluded that the apparent holes were actually closed by another body layer and represented the base of the spines that had been detached, rather than the gills.
The spines are thought to have been used by the Saccorhytus to capture prey, although their potential for deterring predators is evident.
In light of this and other evidence from the reconstructions, the authors classify Saccorhytus as a protostome (i.e. mouth shapes first), more specifically, they think it is an ecdysoszoanwhose modern representatives include insects, shellfish And nematode wormsnone of whose representatives are likely to be satisfied with the kinship.
More concerned with making the family tree fair than respectable, the co-lead authorthe Professor Shuhai Xiao by Virgina Tech, he wants to find the real first deuterostome.
“We are back to square one in finding the first animal with a secondary mouth. The next oldest deuterostome fossil [sospetto] is nearly 20 million years younger. “
Xiao said in a declaration.
On the other hand, no previously hidden anus has been revealed by the harsh light of the X-rays, and since Saccorhytus is unlikely to have stored their wastes inside until death, the most likely explanation seems to be that all that it was not used it returned as it had entered. A more common approach now if you consider a night at the disco on Saturday night …
One might think that Saccorhytus simply had the misfortune to evolve before a bright spark invented advanced anus technology, however Xiao has disproved this:
“This is a truly unexpected result because the group of arthropods has an intestine that extends from the mouth to the anus. The membership of the Saccorhytus in the group indicates that it has regressed in evolutionary termsgiving up the anus that his ancestors would have inherited ”.
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