Death mask of ancient creatures

  Imagine that when you die, a mask will grow. This mask can protect your face for millions of years. In a way, this happened to the oldest animal on our planet. Paleontologists have discovered that after these animals die, they will be wrapped in a “death mask” made of pyrite. The soft corpses will not rot, can be preserved for a long enough time, and slowly become fossils.
   In the Ediacaran Period, between 575 million and 541 million years ago, these creatures spread all over the earth. They look like aliens: for example, the Kimbera is like an avocado wearing a garter belt; the Dickinsonian jellyfish is like a cross between pancakes and earthworms. Biologists have no idea where to place this group in the evolutionary tree-only part of them are animals, and some of these animals are likely to be the ancestors or close relatives of all subsequent animals. Another puzzling question is how Ediacarans became fossils, because most of them are soft creatures. Such creatures are easy to decay quickly, so they rarely become fossils after death.
   To solve this mystery, a team led by Brant Gibson, a paleontologist at Vanderbilt University, replaced the Ediacaran biota with sea anemones (considered the most similar to Ediacarans in modern life). A simulation experiment was carried out. Researchers placed the carcasses of sea anemones in a seawater tank to mimic the chemical environment of the ancient ocean. They observed that iron-rich pyrite deposited around the carcass in about a month. However, the shield did not completely prevent the decay of the body, for example, the tentacles of the sea anemone “disappeared soon.” Gibson pointed out that this result indicates that the Ediacaran fossil may not be the complete appearance of the original creature. Completing the missing parts is crucial to determining the position of these strange creatures on the evolution tree.