One of the very first animals on our planettrilobites are considered. This is the name of the class of extinct arthropod creatures that lived in the vastness of the earth's oceans about 450 million years ago. If you have ever seen wood lice, then you can surely imagine these ancient animals. They were perfectly adapted to life at the bottom: their flattened body was covered with a powerful shell, a complex system of eyes was located on the upper side of the body, and their mouth and legs were located on the lower one. Despite the fact that these creatures lived many millions of years ago, scientists were able to find many fossils. They know a lot of interesting things about their lifestyle, but the exact structure of their bodies for researchers still remains a mystery. For example, scientists for a long time could not understand whether trilobites breathed. Recently, the answer to this question was finally found. Respiratory organs in trilobites were located on their legs.
Who are the trilobites?
Trilobites were a very broad class of animals.At the moment, scientists know about the existence of more than 10 thousand fossil species. The body length of trilobites could reach 90 centimeters. Researchers know that there were crawling and burrowing species. They bred by laying eggs and fed on either small invertebrates or plankton. Most trilobites were predators, but instead of jaws, they used special appendages at the base of the limbs. Many species were able to curl up into a ball and thereby defend themselves from predators. Today woodlice have this ability.
Fossils are often found by scientiststrilobites. They are usually found in China, Canada, the United States and Germany. The existence of trilobites became known in 1771, thanks to the works of the German scientist Johann Walch. Translated from Latin, the word "Trilobita" can be translated as "three-part". And this is a very apt name, because the bodies of trilobites consisted of three parts: head, torso and tail.
Trilobite body structure
So, we already well know the general features of trilobites.Only now, for many years, scientists could not understand exactly where their respiratory organs were located. Recently, while studying a trilobite fossil of the species Triarthrus eatoni, scientists made a very unexpected discovery. After examining the well-preserved prints of the limbs, they came to the conclusion that trilobites breathed with the help of their legs. According to the author of the scientific work, Melanie Hopkins, structures about 30 micrometers in size can be found on the limbs of ancient creatures. Such small irregularities are difficult to detect even under a microscope.
Structures in the upper limb of trilobitesin their shape resemble gills. Many modern arthropods, such as crabs, have similar structures. Apparently, they were necessary for trilobites to saturate the hemolymph circulating inside their body with oxygen. Hemolymph is usually called the liquid that is in the vessels of invertebrates. It serves the same function as the blood inside humans and other mammals.
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Unexpected discovery of scientists
This is a very unexpected discovery even for themselvesscientists. According to them, the limbs are far from the best place for the location of the respiratory organs. As we have already found out above, trilobites led a crawling or burrowing lifestyle. During any movement, the breathing pores could become clogged with dirt. So some people do not believe in the veracity of this discovery - if the gills were on the limbs, the trilobites obviously could not live long. However, there is a possibility that these creatures had a mechanism for clearing the respiratory pores. It's just that scientists have not yet found signs of its presence.
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Trilobites have lived on our planet for millions of yearsback, so their lives are still partly shrouded in mystery. Scientists have discovered group fossils many times, where these ancient creatures stand strictly one after another, as if in line. Almost they behaved this way, researchers were not clear for a long time. However, the answer was found in 2019 - trilobites did not stand in line, but performed actions that were vital for themselves. In short, moving in a close lane helped them cover long distances. You can read more about this and trilobites in general at this link.