The discovery of a newly extinct mollusk species that lurked on the ocean floor 500 million years ago is providing new insight into the early days of this diverse group of animals. Shishania aculeata Some early mollusks were flat, armored, slug-like creatures that showed no distinctive shells seen in snails today. clamsThe species was also covered in hollow, cone-shaped spines called spicules. The study was published in the journal Nature on August 1. Science.
Shishania The new species was discovered thanks to well-preserved fossils found in Yunnan province in southern China, and lived during the Early Cambrian period, about 514 million years ago. Shishania The cones studied by the team were several centimetres long and had sharp, pointed cones. KitchenThis crunchy substance is also found in the shells of modern insects, crabs, and even some mushrooms.
The fossil, preserved upside down, indicates that it likely had muscular legs similar to those of a slug. Shishania It is thought to have used its legs to crawl along the ocean floor, and unlike most mollusks, it did not have a shell covering its body.
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Modern mollusks come in many different forms, including snails, clams, and highly intelligent cephalopods like squids and octopuses. All of this biodiversity developed rapidly during the Cambrian explosion, an event that occurred Approximately 530 million years ago This was a time when all the major groups of animals were rapidly diversifying. But the speed of this change meant that very few fossils remained to tell the story of early mollusks’ evolution. Shishania It represents a very early stage in mollusc evolution.
“Understanding what the common ancestor of animals as different as squid and oysters looked like is a major challenge for evolutionary biologists and paleontologists, and it cannot be solved by studying only species that are alive today,” said study co-author Luke Parry, a paleontologist at the University of Oxford in the UK. It said in a statement.Shishania “This discovery provides a unique look into a period of mollusc evolution where few fossils remain, and tells us that the earliest mollusc ancestors were armoured, spiny slugs, before the evolution of the shells seen in modern snails and clams.”
Shishania Their bodies are made up of soft tissue, which doesn’t usually preserve well in the fossil record, so some of the specimens were poorly preserved and a bit difficult to study.
“At first I thought the thumb-sized fossil was unremarkable, but under a magnifying glass it looked strange, spiky and totally different from any fossil I’d ever seen,” says study co-author Zhang Guangxu, a recent doctoral graduate from China’s Yunnan University, where the fossil was discovered. It said in a statement“At first, we called it the ‘plastic bag’ because it looked like a small rotten plastic bag. When we found more of the fossil and analysed it in the lab, we found that it was a mollusc.”
Covering the body Shishania aculeata (Right). Credit: G Zhang/L Parry.
Shishania Inside the spines is a system of ducts less than a hundredth of a millimeter in diameter. The base of the cone secretes microvilli, tiny projections of cells that increase surface area. Microvilli are found on the human tongue and intestine and aid in food absorption.
“We found microscopic details inside the cone-like spines that cover its body. Shishania “We may find evidence of how they were secreted while alive,” Parry said. “This kind of information is very rare, even in very well-preserved fossils.”
team is Shishania How to secrete hard parts Natural 3D Printer They can change body parts depending on the animal’s needs. In this way, some invertebrates can secrete hard parts that serve all sorts of functions, from defense to aiding in locomotion.
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Chitons (the stiff spines and setae of modern mollusks) are made of the mineral calcium carbonate rather than organic chitin. ShishaniaSimilar chitinous setae are also found in lesser known animal groups such as brachiopods and bryozoans, which, together with mollusks and annelids (modern earthworms and their close relatives), form the crown fauna.
“Shishania “This fossil shows us that the spines and spicules we see today in chitons and aplacoid mollusks evolved from organic bones, like those in annelids,” Parry said. “These animals are now very different from each other. Shishania It tells us what they looked like a long time ago, just after they diverged from a common ancestor.”
