Lunataspis is the oldest known xiphosuran, with two known species both dating from the late Ordovician (latest Sandbien for L. borealis to earliest Hirnantian for L. aurora).

Discovery and species

The type species, L. aurora, was described from remains found in the Konservat-Lagerstätten deposits of the Stony Mountain Formation, central Manitoba by David Rudkin, Graham Young and Godfrey Nolan, from fossils found in northern Manitoba, Canada in 2005. The specific name aurora is Latin for 'dawn' and is also eponymous with the mythological Roman goddess. The deposit dates from the Late Ordovician, earliest Hirnantian c.. A second species, L. borealis, was described in 2022 based on three specimens, including an adult (ROM IP 64616) and two juveniles or subadults (ROM IP 64617 and ROM IP 64618). All specimens were found in the upper member of the Gull River Formation in Kingston, Ontario, dating from the latest Sandbian, late Ordovician, c. . This site was a warm-water platform shelf at the time near the paleo-equator.