''Acaste'' is a genus of extinct

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

of the order

Phacopida Phacopida ("lens-face") is an order of trilobites that lived from the Late Cambrian to the Late Devonian. It is made up of a morphologically diverse assemblage of taxa in three related suborders. Characteristics Phacopida had 8 to 19 thoraci ...

which lived throughout the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

period (

Wenlock Group The Wenlock Group (Wenlockian), in geology, is the middle series of stratum, strata in the Silurian (Upper Silurian) of Great Britain. This group in the typical area in the Wales, Welsh border counties contains the following formations: Much Wenlo ...

). Though many species had been included, it now has only one species, ''Acaste downingiae''. It is characterized by a convex dorsal surface, an absence of spines, a shortening of the head-shield and a general rounding off of all angles.H H Swinnerton - ''Outlines of Palaeontology'', Edward Arnold (Publishers) Ltd, 1972 (p. 247) .

Etymology

* ''A. lokii'' is named after

Loki Loki is a Æsir, god in Norse mythology. He is the son of Fárbauti (a jötunn) and Laufey (mythology), Laufey (a goddess), and the brother of Helblindi and Býleistr. Loki is married to the goddess Sigyn and they have two sons, Narfi (son of Lo ...

, the Norse god of mischief. Loki tricked the blind god

Höðr Höðr ( , Latin Hotherus; often anglicized as Hod, Hoder, or Hodur) is a god in Norse mythology. The blind son of Odin, he is tricked and guided by Loki into shooting a mistletoe arrow which was to slay the otherwise invulnerable Baldr. Accord ...

to kill the god of beauty

Baldr Baldr (Old Norse also Balder, Baldur) is a god in Germanic mythology. In Norse mythology, he is a son of the god Odin and the goddess Frigg, and has numerous brothers, such as Thor and Váli. In wider Germanic mythology, the god was known in ...

, and so started the demise of the world (or

Ragnarök In Norse mythology, (also Ragnarok; or ; ) is a foretold series of impending events, including a great battle in which numerous great Norse mythological figures will perish (including the Æsir, gods Odin, Thor, Týr, Freyr, Heimdall, a ...

). This

epithet An epithet (, ), also a byname, is a descriptive term (word or phrase) commonly accompanying or occurring in place of the name of a real or fictitious person, place, or thing. It is usually literally descriptive, as in Alfred the Great, Suleima ...

was chosen by Edgecombe because it is based on the cephalon of ''A. longisulcata'', which has turned out to be a mixed collection. The pygidium of ''A. longisulcata'' belongs to a

Phacopoidea Phacopoidea is a superfamily of trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossi ...

. * ''A. zerinae'' is named in honor of Zerina Edgecombe, the wife of the species author.

Taxonomy

Species previously assigned to ''Acaste''

Some species originally designated to ''Acaste'' have now been reassigned to other genera. * ''A. birminghamensis'' = ''Llandovacaste birminghamensis'' * ''A. constrictus'' = '' Acastoides constricta'' * ''A. cordobesa'' = ''Pennaia verneuili'' * ''A. henni'' = '' Acastoides henni'' * ''A. verneuili'' = ''Calmonia terrarocenai''

References

Acastidae Phacopida genera Silurian trilobites Trilobites of Africa Trilobites of Oceania Silurian first appearances Early Devonian genus extinctions Wenlock series fossils {{phacopida-stub