Myriapods are a diverse group of arthropods, including millipedes, centipedes, pauropods, and symphilans. They are known for their many legs and repugnance glands. The oldest known land animal is a myriapod, Pneumodesmus newmani, which lived in Scotland 428 million years ago. Myriapods are mostly found in moist forests and play an important role in decomposing plant material.
Myriapods are a group of arthropods that includes millipedes, centipedes, pauropods, and symphilans. While each of these subgroups is believed to be monophyletic (descended from a common ancestor), it is less certain that the entire group is monophyletic. A specimen of a rare millipede found in central California, Illacme plenipes, had 750 legs, the most of any recorded animal, but most myriapods have between 20 and 400 legs.
The distinguishing feature of myriapods is their many legs, but many of them have other common features, such as repugnance glands, which produce an irritating liquid used to deter predators. This liquid often contains benzoquinones, which can blister human skin.
The myriapods are notable for including the oldest known land animal, Pneumodesmus newmani, a millipede that lived in Scotland 428 million years ago, during the Middle Silurian. It was known to be a terrestrial animal due to the presence of spiracles, small holes used to breathe air. The 1 cm (0.4 in) fossil fragment was discovered by a bus driver, Mike Newman, who was a fossil hunter as a hobby. It was found to be 20 million years older than the previous oldest known land animal, a spider-like fossil that has also been found in Scotland. As Scotland has been extensively altered by glaciers throughout its history, it has left ancient strata fully exposed and ready for fossil hunting.
Of the myriapods, millipedes are mostly carnivorous (reflected in their fearsome appearance), while millipedes primarily consume detritus, although some species eat other small arthropods. Sinphylans and pauropods are small soil arthropods that superficially resemble millipedes and move rapidly among soil grains.
All myriapods are most numerous in moist forests, where they play an important role in decomposing plant material, creating nutrient-rich debris for bacteria to break down further. If you lift a log in a damp forest, you’ll likely see dozens of myriapods coming out.
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