Euglyphid testate amoebae (rhizaria: euglyphida) from an arctic eocene waterbody: evidence of evolutionary stasis in plate morphology for over 40 million years.

Well-preserved siliceous plates representing multiple species of euglyphids are described from a Middle Eocene maar lake deposit located near the Arctic Circle in northern Canada. Siliceous plate morphotypes including scutiform, rectangular, hexagonal, oval and circular body forms, six apertural plate types containing from five to thirteen teeth and spine plates, are documented. Many plate types bear resemblance to those found on modern species as well as ones documented from Miocene sites. These findings extend the known geological record for euglyphids and support the concept of evolutionary stasis in regards to plate morphology over much of the Cenozoic. Future use of these euglyphid remains, in conjunction with other microfossil assemblages, for reconstructing historical conditions within the maar lake is discussed.