About 300 million years ago, a small reptile settled down in the mud, leaving an impression that became only the second fossilized butthole ever found.
The title of a paper recently published in Current Biology, "The earliest reptile body impressions with scaly skin," buries the lede. Amid the tail and foot impressions, the researchers discovered the oldest known fossilized cloaca. If you aren't a bird or reptile enthusiast, you might not be familiar with the term. Both have a cloaca — a single opening for waste and reproduction. The egg-laying mammals, or monotremes, the platypus and echidna, also have cloacae.
One of the authors discusses and displays the cloaca at about the three-minute mark in this video. The find is 170 million years older than the previous record-holder, which was found in 2021. Jakob Vinther, a paleontologist at the University of Bristol in England, describes the find to Scientific American as being "… as rare as hens' teeth, and finding another one is exciting to say the least."
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