Trilobita$505824$ - traduzione in olandese
![Sao hirsuta]]''](https://commons.wikimedia.org/wiki/Special:FilePath/1911 Britannica-Arachnida-Sao hirsuta.png?width=200 "Sao hirsuta]]''")
![[[Redlichiida]], such as this ''[[Paradoxides]]'', may represent the ancestral trilobites](https://commons.wikimedia.org/wiki/Special:FilePath/BLW Trilobite (Paradoxides sp.).jpg?width=200 "[[Redlichiida]], such as this ''[[Paradoxides]]'', may represent the ancestral trilobites")
![A trilobite fragment (T) in a thin-section of an Ordovician [[limestone]]; E=[[echinoderm]]; scale bar is 2 mm](https://commons.wikimedia.org/wiki/Special:FilePath/BioclastsBiosparite.jpg?width=200 "A trilobite fragment (T) in a thin-section of an Ordovician [[limestone]]; E=[[echinoderm]]; scale bar is 2 mm")
![Ogygopsis klotzi]]'' from the Mt. Stephen Trilobite Beds ([[Middle Cambrian]]) near [[Field, British Columbia]], Canada](https://commons.wikimedia.org/wiki/Special:FilePath/Cambrian Trilobite Olenoides Mt. Stephen.jpg?width=200 "Ogygopsis klotzi]]'' from the Mt. Stephen Trilobite Beds ([[Middle Cambrian]]) near [[Field, British Columbia]], Canada")
![''[[Cruziana]]'', fossil trilobite-burrowing trace](https://commons.wikimedia.org/wiki/Special:FilePath/Cruziana2.jpg?width=200 "''[[Cruziana]]'', fossil trilobite-burrowing trace")
![''[[Elrathia kingii]]'' growth series with holaspids ranging from 16.2 mm to 39.8 mm in length](https://commons.wikimedia.org/wiki/Special:FilePath/Elrathia kingii growth series.jpg?width=200 "''[[Elrathia kingii]]'' growth series with holaspids ranging from 16.2 mm to 39.8 mm in length")
![Ogygiocarella debuchii]]'' by Rev. Edward Lhwyd, made in 1698](https://commons.wikimedia.org/wiki/Special:FilePath/Flatfish Lhwyd.jpg?width=200 "Ogygiocarella debuchii]]'' by Rev. Edward Lhwyd, made in 1698")
![An enrolled phacopid trilobite ''[[Flexiclaymene]] meeki'' from the Upper Ordovician of Ohio](https://commons.wikimedia.org/wiki/Special:FilePath/Flexicalymene meeki cephalon view.JPG?width=200 "An enrolled phacopid trilobite ''[[Flexiclaymene]] meeki'' from the Upper Ordovician of Ohio")
![Pitted fringes on the cephalon of the trinucleoidean ''[[Lloydolithus]] lloydi''](https://commons.wikimedia.org/wiki/Special:FilePath/Lloydolithus lloydi.JPG?width=200 "Pitted fringes on the cephalon of the trinucleoidean ''[[Lloydolithus]] lloydi''")
![''[[Rusophycus]]'', a "resting trace" of a trilobite; Ordovician of southern Ohio. Scale bar is 10 mm.](https://commons.wikimedia.org/wiki/Special:FilePath/RusophycusOrdovician.jpg?width=200 "''[[Rusophycus]]'', a \"resting trace\" of a trilobite; Ordovician of southern Ohio. Scale bar is 10 mm.")
![''[[Meroperix]]'', from the Silurian of [[Wisconsin]]](https://commons.wikimedia.org/wiki/Special:FilePath/Scutelluid trilobite.jpg?width=200 "''[[Meroperix]]'', from the Silurian of [[Wisconsin]]")
![''[[Cheirurus]]'' sp., middle [[Ordovician]] age, [[Volkhov River]], [[Russia]]](https://commons.wikimedia.org/wiki/Special:FilePath/Trilobite Ordovicien 8127.jpg?width=200 "''[[Cheirurus]]'' sp., middle [[Ordovician]] age, [[Volkhov River]], [[Russia]]")
![Walliserops trifurcatus]]'', from Jebel Oufatene mountain near [[Fezzou, Morocco]]](https://commons.wikimedia.org/wiki/Special:FilePath/Trilobite Walliserops trifurcatus.jpg?width=200 "Walliserops trifurcatus]]'', from Jebel Oufatene mountain near [[Fezzou, Morocco]]")
.png?width=200 "Number of families, Middle Devonian to Upper Permian. Proetida – brown, Phacopida – steel blue, Lichida – clear blue, Harpetida – pink, Odontopleurida – olive and Corynexochida – purple")
.png?width=200 "Illustration of the three types of hypostome. Doublure is shown in light gray, the inside surface of the cephalon in dark gray, and the hypostome in light blue. The glabella is outlined in red broken lines.")
![tagmata]]): 1 – cephalon; 2 – thorax; 3 – pygidium. Trilobites are so named for the three longitudinal lobes: 4 – right pleural lobe; 5 – axial lobe; 6 – left pleural lobe; the antennae and legs are not shown in these diagrams](https://commons.wikimedia.org/wiki/Special:FilePath/Trilobites main morphological groups.svg?width=200 "tagmata]]): 1 – cephalon; 2 – thorax; 3 – pygidium. Trilobites are so named for the three longitudinal lobes: 4 – right pleural lobe; 5 – axial lobe; 6 – left pleural lobe; the antennae and legs are not shown in these diagrams")
![Isotelus rex]]'', the largest-known trilobite, from the middle to upper [[Ordovician]] of [[North America]]](https://commons.wikimedia.org/wiki/Special:FilePath/Worlds largest trilobite.jpg?width=200 "Isotelus rex]]'', the largest-known trilobite, from the middle to upper [[Ordovician]] of [[North America]]")
Definizione
Wikipedia
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period (521 million years ago) and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described.
By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, they left an extensive fossil record. The study of their fossils has facilitated important contributions to biostratigraphy, paleontology, evolutionary biology, and plate tectonics. Trilobites are often placed within the arthropod subphylum Schizoramia within the superclass Arachnomorpha (equivalent to the Arachnata), although several alternative taxonomies are found in the literature. More recently they have been placed within the Artiopoda, which includes many organisms that are morphologically similar to trilobites, but are largely unmineralised.
Trilobites evolved into many ecological niches; some moved over the seabed as predators, scavengers, or filter feeders, and some swam, feeding on plankton. Some even crawled onto land. Most lifestyles expected of modern marine arthropods are seen in trilobites, with the possible exception of parasitism (where scientific debate continues). Some trilobites (particularly the family Olenidae) are even thought to have evolved a symbiotic relationship with sulfur-eating bacteria from which they derived food. The largest trilobites were more than 45 centimetres (18 in) long and may have weighed as much as 4.5 kilograms (9.9 lb).
