A speck-sized marine creature with a bag-like appearance that lived some 540 million years ago is the earliest-known prehistoric human ancestor. Sounds crazy! Well, it indeed is crazy! Meet Saccorhytus coronarius that lived some 540 million years ago in the Fortunian stage of Cambrian period.
About Saccorhytus coronarius
Saccorhytus coronarius is a speck-sized marine critter that lived some 540 million years ago. Dwelling in the seawater, this creature did not have an anus. Yes, you read it right. The creature was devoid of an anus. It has a bag-like appearance.
The Saccorhytus coronarius has its very own family called Saccorhytidae. It has is very own genus and even species – Saccorhytus coronaries. The name comes from a combination of Latin and Greek. The name was selected carefully because of its sac-like body that has a wrinkled appearance. In Latin, sac is called ‘Saccus’. The Greek word for wrinkle is ‘rhytis’. So now you can guess why such a name.
This ancient animal, according to the scientists, is the most primitive known example of a deuterostome. Wondering what a deuterostome is? Well, it is one of the major groups that is found in animal kingdom. The deuterostomes are again divided into echinoderms and chordates. The deuterostomes also include hemichordates, vetulocystids and vetulicolians.
Echinoderms are the spiny skinned sea urchins, starfish and all their known relatives. Chordates on the other hand include all fish species and all vertebrates. We humans are vertebrates.
This makes Saccorhytus coronarius the earliest known relative of humans and not just humans! Saccorhytus coronarius is also the earliest known ancestor of a wide range of species that lived over hundreds of millions of years.
Sounds interesting so far? Read on…
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Saccorhytus coronarius Discovery and Reconstruction
The fossilized specimen of Saccorhytus coronarius were found at Kuanchuanpu Formation, Hexi, Xixiang County, Shaanxi Province, central China. Total 45 specimen were collected and all of them were phosphatized. The specimen thus collected were then studied by a large number of scientists globally. The experts who studied these fossils were from:
- University of Cambridge, UK.
- University of Kassel, Germany.
- Northwest University, USA.
- China University of Geosciences.
- Xi’an Shiyou University, China.
After the experts analyzed the specimen, the submitted a collective study and the research paper was published in the journal Nature. The research paper was published on January 30, 2017.
Prof. Simon Conway Morris – the lead co-author of the paper said that the collected fossils, when looked upon with naked eyes, look nothing more than tiny black grains. However, when the fossils were put under electron microscope some unbelievable details popped up.
According to the researchers, Saccorhytus coronarius is now giving them some remarkable insights into the early evolutionary stages of the group that give way for fish and eventually humans. It is interesting to note that before the discovery of the creature, the earlier deuterostomes that were discovered were as old as 520 million years to 530 million years. This newly discovered deuterostome on the other hand is older at 540 million years.
Problem is that the intense diversity of vertebrates, echinoderms and hemichordates makes it extremely difficult for the researchers to find out just how the ancient common ancestor of all the animals belonging to the deuterostomes looked like.
So, what the researchers did with the collected samples is that they isolated the fossils of the creature from the rocks and then put the fossils under electron microscope and then under CT scanner. This allowed them to sketch the detailed picture of how the creature looked like when it was alive.
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Saccorhytus coronarius – Body Structure
Once the structure of the Saccorhytus coronarius was rebuilt by the paleontologists, they found something stunning. It had characteristics and features that the scientists assumed there would be in prehistoric deuterostomes.
Here are the physical characteristics of creature as per the researchers:
- Size: About a millimeter.
- Lived: On seabed between sand grains.
- Body: Bilaterally symmetrical – a feature inherited by descendants – even by humans.
- Skin: Relatively flexible and covered the body.
According to the researchers, the Saccorhytus coronarius had a hemi-ellipsoidal body. The maximum length attained by the creature was 1,300 μm. The maximum width attained was 800 μm while the maximum height attained was 900 μm. The bilateral symmetry, according to the scientists, was revealed only by a handful of specimen as most of the material were actually crushed.
The bilaterally symmetrical body shape of the creature suggested that the critter had some kind of musculature meaning they had contractile movements and wriggling was the mechanism they used to move around.
Saccorhytus coronarius – Eating and Discharging Waste
The most striking of all features was its large mouth. The mouth was disproportionately big compared to the rest of the body. The researchers believed that it ate by opening its wide mouth and taking in the food material that might have included other creatures as well.
The scientists also found conical structures on the body of the creature. This led the scientists to believe that the structures were designed to allow an escape route for the water that entered through the mouth while eating and perhaps, these structures eventually, over millions of years of evolutionary process, evolved in gills that can be seen in today’s fish.
The most perplexing discovery was the absence of any signs of anus. Yes, Saccorhytus coronarius perhaps didn’t have an anus. So, the most likely route for discharging waste was the same route that was used for taking in food – that is mouth. Well, that’s kind of unappealing for us.
Final Words on Saccorhytus coronarius
It is really hard to believe that we humans evolved from Saccorhytus coronarius – a tiny creature that wriggled around in seabed. It is hoped that scientists can reconstruct the evolution of humans from these tiny critters. One thing we are thankful about is that unlike the Saccorhytus coronarius, we have outgrown the no-anus stage else, it would have been really disgusting!