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The inner part of human teeth may have arisen from an unlikely place: sensory tissues in fish that were swimming in the Earth’s oceans 465 million years ago.
While our teeth are covered with solid enamel, the inner layer of the teeth is responsible for carrying the sensory information of the nerves – which interact with the pressure of the solid sting, pain or changes such as severe cold or sweetness.
When trying to determine the assets of the teeth, one of the many possibilities that researchers have seen over the years was that the teeth had evolved from bumps on armored external structures on old fish. But the real purpose of the structures, called Odontodes, was not clear.
Now, a new study and a three -dimensional survey of excavations resulted in evidence that external bumps contain it, which are likely to help hunt them on their surroundings. The scientists reported the results of Wednesday in the magazine nature.
“Covered with these sensitive tissue, perhaps when you collide with something, you can feel pressure, or perhaps that is when the water is very cold and he needed to swim elsewhere,” said Dr. Yara Hardy, a post -PhD researcher in the biology department of living organisms and anatomy in an email.
During its analysis, the team also revealed the similarities between Odontodes and the features called Sensilla, which are found as sensory organs in modern animal shells such as sea cancer and shrimp, and can be found in fossilized invertebrate arthropods. Haridy said that the development of the Oudong in the fish, which are vertebrates and allergies in the arthropods, which are invertebrates, are a major example of evolutionary rapprochement – when similar features develop independently in different animal groups.
Haridy said: “These non -jaws and arthrops (extinct marine arthropods) have a very common common predecessor, no most likely it has no solid parts at all.” “We know that vertebrates and arthropods have evolved independently and surprisingly that they have evolved similar sensory mechanisms built into their solid skeletal independently.”
While arthropods have kept their senses, Adwan Odontodes is the direct ectops of teeth in animals.
When researchers compared Sensilla and Odontodes, they also reached another discovery: one of the species, which was one day ancient fish, was actually articulated.
Searching for the oldest vertebrates
Harridi’s original goal was to solve the mystery of the oldest vertebrate animal in the fossil record. She approached museums throughout the country and asked her if she could wipe any fossil samples they have from the Cambrian period, 540 million years ago to 485 million years.
Next, she settled in the National Argonne Laboratory, where she used the advanced photon source to capture high -resolution computers, or CT.
Haridy said: “It was a night in the speed of the particles, it was fun.”
A dentymouth catfish’s brown catfish, nerves (green), which allows the transmission of sensory information from the nervous system. Yara Hardy/Chicago University
At first glance, a fossil looked from a creature called AnatolePis as if it were the vertebrate fish – and indeed, Previous search from 1996 Determine it as one. Hardy and her colleagues noticed that there is a series of pores filled with materials that seem urgent.
Haridy said: “We were going to each other, like“ Oh my God, we have done it finally. ”This was the first teeth -like structure in the tissues of the vertebrates from the Cambrian. Therefore, we were very excited when we saw the signs of Telltale on what looks like ivory. “
To confirm their discovery, the team compared wiping operations with those in other old excavations, as well as modern sea cancer, wires, beetles, sharks, pincin, and even the SUCKERMOUTOH mini fish that sparked Hardy itself.
These comparisons showed that AnatolePis is very similar to articular fossils, including one of the Milwaukee General Museum. What the team believed was pipes lined with ivory were actually more similar to Sensilla.
But they found Adwan containing teeth in old fish like Eriptychius And asraspis during surveying operations.
The ambiguity about the true nature of AnatolePis has arisen from the fragmented nature of excavations. Haridy said the most complete pieces are only about 3 millimeters (0.1 inches).
Dental CT scan shows on Catshark. These dental structures are associated with the nervous system. Yara Hardy/Chicago University
However, the new surveying operations enabled a three -dimensional look at the excavations, and revealed its internal dissection.
“This explains to us that” teeth “can also be sensual even when they are not in the mouth,” Haridy said. “Therefore, there is a sensitive shield in these fish. There is a sensitive shield in these arthropods. This explains the confusion with these early Cambron. People thought this was the first vertebrates, but it was actually articulated.”
Dr. Richard Deren, a post -PhD research fellow at the Natural Biological Diversity Center in Leiden, the Netherlands, said the modern photography used in the study is the solution to the discussion about AnatolePis. Dearden did not participate in the new search.
“(The authors of the study) use modern photography methods to try to settle this question, and collect a wonderful collection of comparative data to prove that AnatolePis is not actually paragraphs,” Derdin said in an email.
A shield against elements
Armed jaws such as AstrasPIS, Eriptychius and ancient arthropods such as AnatolePis are coexisted in the muddy shallow seas in the Ordovician period, which occurred between 485.4 million and 443.8 million years.
Other contemporaries of these animals included large header such as giant squid, as well as huge marine scorpions. Features like Odontodes and Sensilla would help fish and arthropods distinguish between predators from prey.
The illustration of this artist AstrasPIS is exposed to attack by Megalograptus Sea-Scorpion in dark shallow waters. The glow of the interactive external structures of animals is how they both would feel the world around them. – Brian Ing/living versions
“When you think about an early animal like this, swim around it with shields, you should feel the world. This was a very intense predator and to be able to feel the properties of the water around them. It was very important,” said the prominent study author Dr. Neil Schopene, Robert R. Bensley, Professor of Membership Service at the University of Chicago, in a statement. “Therefore, here we see that invertebrates with shields such as crabs in the hallway need to feel the world as well, and this only happens in the same solution.”
Haridy said that many modern fish have Odonio fish, while sharks, signs and some catfish are covered in small teeth called teeth, which cause their skin to feel like sanding paper.
Haridy studied the tissues of the fish that raised it and realized that its teeth are connected to the nerves in the same way that the teeth are located in animals. When comparing teeth, iodets and allergies, they were all incredibly similar.
“We believe that the first vertebrates, these large armored fish, had very similar structures, at least formally. They look similar in old and modern hinges, because they all make this metal layer that outperforms their soft tissues and helps them to feel the environment,” Haridy said.
The genes needed to form Odontodes also produced sensitive teeth in animals – including humans – later, according to the authors of the study.
The authors of the study indicated that the results support the idea that sensory structures first appeared on external structures, which then provided genetic information that can be used to create teeth because they have become a necessary part of life.
“Over time, jaws have evolved, and it became useful to have pointed structures around them and in the mouth,” Haridy said. “Some fish were slowly with the jaws with pointed additives on the edge of the mouth, then in the end some of them were in the mouth directly and then lost across the body. The relationship between the oditat and teeth is constantly clarified by the new fossils and modern heredity.”
A CT scan shows in front of the solid teeth -like skiing on its skin (as shown in orange). Yara Hardy/Chicago University
Dr. Lauren Salan, an assistant professor at the Okinawa Unit of Science and Technology in Japan, said that the new research improves the timeline of the first appearance of solid tissues and early fish grandparents by removing Anatolibis from the fish tree for life. Salan, who did not participate in the new study, said that it also raises an interesting new hypothesis that dental -like spoilers have evolved to discover prey, friends or predators in the water.
“This is a real challenge to clear assumptions that it seems that solid tissues such as teeth and structures such as standards and teeth have evolved (primarily) to protect the body or nutrition in the throat,” Salan said. “Instead, may have been” modified “(later modified) for these uses, such as how the limbs evolve before using them to walk on the ground. It is also interesting to see the degree of rapprochement between early armored hinges and fish, and raises questions about the amount of ecological overlap that occurred between these two groups.”
Haridy wants to continue searching for fossils that can lead to the oldest vertebrates, given that researchers expect that there will be a previous vertebrate of AstrasPis and Eriptychius. Chopin said in an email that although they did not discover this through this research, they have achieved worthy results.
“We felt disappointed because (AnatolePis) was not a poor, but we were surprised by the new ideas that arose.” “We took it in a completely new direction. This is a science.”
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