Trilobite Order Proetida
Proetid Trilobites |
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| The Proetids persisted the longest and were the last order of the trilobites to go extinct. These last survivors arose in the Ordovician and died out during the great Permian Extinction. They
were relatively smaller trilobites that, like the trilobites
of order Phacopida, often exhibited pits and tubercles on their
exoskeletons, particularly on their glabella. Unlike some trilobites
of the order Phacopida that have schizochroal eyes, the proetids
Proetida (pronounced Pro-eh-tee-da) is often included in subclass Librostoma along with what are now Orders Ptychopariida, Asaphida, and Harpetida that were united as Order Ptychopariida, a huge and paraphyletic group (see the 1959 Treatise on Invertebrate Paleontology). The subclass Librostoma was erected in 1990 by Fortey (1990) to encompass these orders that share a natant hypostomal condition. Subsequently, Ebach & McNamara (2002) erected order Harpetida because its members lack a rostral plate and have a marginal facial suture.
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