When sponges did not have skeletons

toNear coral reefs and sponges. It is clear that current zoological research values ​​little-known animals. Or rather, those that many do not know belong to the animal kingdom. On May 28, review Royal Society Open Science Thus he published a description of a sexual orgy in which corals indulged in a Japanese aquarium. A sight as impressive as the one we reported on. On June 5, it was his turn nature To publish a fascinating article that brings a new, potentially major, piece to an old debate regarding the first sponges, one of the most primitive animals we know of.

Because, let's remember here, sponges are animals. No brain, no muscles, no digestive system. Simply a body built around channels that filter water and expel waste, all connected to the rock. But the nature of the cells Reproduction, with the presence of sperm, or even mode of feeding, indisputably places the nearly 15,000 listed species of the phylum Porifera — its scientific name — in a large family of creatures.

If this question has been settled since the 1850s, there is another controversy that fascinates the “spongeists”: the origin of their favorite animal. Or more precisely, how long has it been around and in what form? Modern genomics makes it possible to go back in time. The hands of this molecular clock point further back to the Cambrian Period, a period of explosion of diversity that began 539 million years ago. Biomarkers found in rocks, which are assumed to be witnesses to the presence of porosity, confirm these data. Sponges appeared at least 650 million years ago. There's one thing missing: fossils. The Precambrian samples were well advanced. In 2021, indeed natureOne article even turned the clock back to 890 million years ago. But the scientific community remains largely skeptical.

Morphological study

The last article is less greedy. The fossil found by the international team (China, the United Kingdom, and the United States), led by Shuhai Xiao, from the Department of Earth Sciences at Virginia Tech in the United States, is located in a range of 551 to 539 million years old. Before the beginning of the Cambrian period, so. To find it, Chinese scientists traveled through the Yangtze Valley in Sichuan. Local farmers use shibantan limestone on building roofs. The fossil discovered on the slab of the pig pen allowed them to target a quarry. There they found their rare gem.

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