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Order Ptychopariida is the most problematic order for trilobite classification. In the 1959 Treatise on Invertebrate Paleontology , [ 60 ] what are now members of orders Ptychopariida, Asaphida , Proetida and Harpetida were grouped together as order Ptychopariida; subclass Librostoma was erected in 1990 [ 61 ] to encompass all of these orders ...
Merlinia is an extinct genus from a well-known class of fossil marine arthropods, the trilobites.It lived during the early part of the Arenig stage of the Ordovician Period, [1] a faunal stage which lasted from approximately 478 to 471 million years ago. [1]
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 ...
Asaphida is a large, morphologically diverse order of trilobites found in marine strata dated from the Middle Cambrian until their extinction during the Silurian. Asaphida contains six superfamilies (Anomocaroidea, Asaphoidea, Cyclopygoidea, Dikelocephaloidea, Remopleuridoidea and Trinucleioidea), but no suborders.
The suborder Calymenina is the most primitive of the Phacopida order and shares some characteristics with the order Ptychopariida, though it is not included in the subclass Librostoma. Phacopida was one of only two trilobite orders (along with the Proetida) to survive the Kellwasser event (Late Devonian extinction) at the Frasnian-Famennian ...
Asaphus kowalewskii (/ˈæsæfʌs ˈkoʊæluːskiː/) is one of the 35 species of trilobites of the genus Asaphus (this particular species is sometimes placed in its own genus, Neoasaphus). Fossils of this species are popular among collectors because of their prominent stalked eyes (termed "peduncles"), many an inch or more in length.
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.
Fossils of the trilobite Ampyx priscus, dating back about 480 million years ago, have been recently described as clustered in lines along the ocean floor. The animals were all mature adults, and were all facing the same direction as though they had formed a conga line or a peloton .