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 have the more common holochroal
eyes. Holochroal eyes closely packed biconvex lenses beneath
a single corneal layer covering all lenses. Each lens is roughly
hexagonal and thus in direct contact with adjacent ones, and
can number into the thousands of lenses. The proetid's thorax
of proetids have between some eight to 22 segments. Many have
pronounced genal spines resembling those of trilobite order
Phacopida.
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. |
Subclass
Librostoma*
Trilobite Order Proetida
- Suborder
Proetina
- Superfamily
Proetoidea
- Superfamily
Aulacopleuroidea
- Superfamily
Bathyuroidea
*
Subclass Librostoma contains Proetida, Harpetida, Ptychopariida,
Asaphida
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Proetid
Trilobite Fossils
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Devonian
Family Proetidae
Alnif, Morocco |
Devonian
Family Proetidae
Mrakib, Morocco |
Devonian
Family Proetidae
Foum Ziguid, Morocco |
Devonian
Family Proetidae
Jebel el, Morocco |
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Devonian
Family Aulacopleuridae
Jorf, Morocco |
Silurian
Family Aulacopleuridae
New South Wales, Australia |
Mississippian
Family Proetidae
Chouteau Formation, Missouri |
Devonian
Superfamily Proetoidea
Family Proetidae
Jorf, Morocco |
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Devonian
Superfamily Proetoidea
Family Proetidae
Jorf, Morocco
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Ordovician
Superfamily Proetoidea
Family Proetidae
Verulam
Formation, Ontario |
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