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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 ...
Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in the second half of the Lower Cambrian, and the last species did not survive the Ordovician–Silurian extinction event. Asaphiscus wheeleri, a Cambrian trilobite of the Superfamily Ptychoparioidea
Over the past 200 years, paleontologists have identified over 22,000 species of trilobites from locations around the world that were once covered by oceans. Trilobites were arthropods, like modern ...
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.
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.
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 ...
Corynexochida is an order of trilobite that lived from the Lower Cambrian to the Late Devonian. Like many of the other trilobite orders, Corynexochida contains many species with widespread characteristics. The middle region of the cephalon (the glabella) is typically elongate, with the sides often spreading forward (pestle-shaped).
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]