They’ve been solving the mystery of the creature without an anus for more than 500 million years

  • Victoria Gil
  • BBC science reporter

image source, Cambridge University


Artist’s reconstruction of Sacorhitos Coronarios, based on original fossil finds.

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.

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