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Sometimes the Nektaspida are considered trilobites, but these lack a calcified exoskeleton and eyes. Some scholars have proposed that the order Agnostida is polyphyletic, with the suborder Agnostina representing non-trilobite arthropods unrelated to the suborder Eodiscina. Under this hypothesis, Eodiscina would be elevated to a new order ...
The trilobite Protolenus is shown in a side view. The digestive system is seen in blue, the hypostome, or mouth structure, in green (far left) and the labrum, a bulbous structure over the mouth ...
Olenoides followed the basic structure of all trilobites — a cephalon (head shield), a thorax with seven jointed parts, and finally a semicircular pygidium. Its antennae were long, and curved back along its sides. Its thin legs show that it was no swimmer, instead crawling along the sea floor in search of prey.
Redlichia is a genus of redlichiid trilobite in the family Redlichiidae, with large to very large species (up to 35 centimetres or 14 inches long).Fossils of various species are found in Lower Cambrian ()-aged marine strata from China, Korea, Pakistan, the Himalayas, Iran, Spain, southern Siberia, and Antarctica, and from Middle Cambrian ()-aged marine strata of Australia.
It is considered unlikely, however, that these factors would be enough to explain the large discrepancy between gill tract size and body size. [ 29 ] It has been suggested instead that the "gill tract" was an organ for breathing air, perhaps actually being a lung , plastron or a pseudotrachea . [ 30 ]
Dalmanites is genus of trilobites with an average (about 8 centimetres or 3.1 inches long), moderately vaulted exoskeleton with an inverted egg-shaped outline (about 1.5× longer than wide). Its headshield (or cephalon ) is semicircular, with robust (genal) spines extending from the side of the cephalon back to approximately the 8th thorax segment.
Triarthrus is an average size trilobite (up to about 5 centimetres or 2.0 inches) and its moderately convex body is about twice as long as wide (excluding spines). Like in all Olenidae, the headshield (or cephalon ) of Triarthrus has opisthoparian sutures , and the right and left free cheeks that they define are yoked.
The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 [5] to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha. Trilobites, in part due to abundance of findings owing to their mineralized ...