Strabopidae
Strabopidae is the only family of the order Strabopida, an extinct group of arthropods known from the Cambrian period.[1] The order Strabopida contains three valid genera and one doubtful, Khankaspis, Paleomerus, Parapaleomerus and Strabops, all assigned in the family Strabopidae.[2] Previously, it also contained the genera Caryon, Lemoneites and Neostrabops, but after a study, they were reassigned as a trilobite, a glyptocystitid echinoderm and a cheloniellid arthropod, respectively.[2] Paleomeridae was also previously included as a family, but after the discovery of a fourth Paleomerus specimen and its study, Paleomeridae was synonymized into Strabopidae.[3] Although often suggested to be closely related to aglaspidids due to their similar morphology, their exact phylogenetic placement is uncertain due to the poor preservation of all known strabopids. A 2013 attempt to place them in a phylogenetic analysis recovered them as part of a polytomy with megacheirans, marrellomorphs, crustaceans and artiopodans.[1] Still, strabopids are often classified as part of the clade Arachnomorpha.[3] In fact, Dunlop & Selden (1998) defined Paleomerus as "perhaps the best model of a primitive arachnomorph".[4] References
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