Generalized eurypsid skull, showing a single fenestra after orbit. j: yugal, p: parietal, po: postorbital, sq: scaly, q: square, qj: quadratojugal.
Euryápsidos (Euryapsida) are a polyphyletic group of sauropsids (reptiles) that are characterized by presenting a single temporal or fenestra fossa on the postorbital bone; the synapsids also have a single fenestra, but located in the lower region of the postorbital.
Several evolutionarily unrelated lineages reached the eurypsid condition independently; among them were included examples of large reptiles of the Mesozoic Era, such as plesiosaurs, ichthyosaurs and placodonts.
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