According to a new study published in the journal Nature, the spikey, wrinkly, anus-less, microscopic organism known as Saccorhytus coronarius is not, in fact, an evolutionary precursor to homo sapiens. "The early Cambrian microscopic animal Saccorhytus coronarius was interpreted as an early deuterostome on the basis of purported pharyngeal openings, providing evidence for a meiofaunal ancestry and an explanation for the temporal mismatch between palaeontological and molecular clock timescales of animal evolution," the researchers explained. "Phylogenetic analyses indicate that S. coronarius belongs to total-group Ecdysozoa, expanding the morphological disparity and ecological diversity of early Cambrian ecdysozoans."
Translation: they analyzed some 500 million-year-old fossils of the spikey, wrinkly, Sac, taking hundreds of microscopic x-rays from all different angles, and reconstructed a 3D model of the creature. Upon closer examination, they realized that the tiny little pores around the mouth of the Saccorhytus coronarius were not, in fact, tiny butt holes, but were actually the remnants of tiny spikes, which the creature used to help feed itself.
As explained on Phys.org:
The researchers believe that Saccorhytus is in fact an ecdysozoan: a group that contains arthropods and nematodes. "We considered lots of alternative groups that Saccorhytus might be related to, including the corals, anemones and jellyfish which also have a mouth but no anus," said Prof Philip Donoghue of University of Bristol's School of Earth Sciences, who co-led the study. "To resolve the problem our computational analysis compared the anatomy of Saccorhytus with all other living groups of animals, concluding a relationship with the arthropods and their kin, the group to which insects, crabs and roundworms belong."
Saccorhytus' lack of anus is an intriguing feature of this microscopic, ancient organism. Although the question that springs to mind is the alternative route of digestive waste (out of the mouth, rather undesirably), this feature is important for a fundamental reason of evolutionary biology. How the anus arose—and sometimes subsequently disappeared—contributes to the understanding of how animal bodyplans evolved.
This lack of asshole made it clear that the Saccorhytus coronarius was not, in fact, related to assholes. I mean humans.
Scientists relieved to discover 'curious' creature with no anus is not earliest human ancestor [University of Bristol / Phys.org]
Saccorhytus is an early ecdysozoan and not the earliest deuterostome [Yunhuan Liu, Emily Carlisle, Huaqiao Zhang, Ben Yang, Michael Steiner, Tiequan Shao, Baichuan Duan, Federica Marone, Shuhai Xiao & Philip C. J. Donoghue / Nature]
