Sprigginidae

{{short description|Extinct family of cephalozoans}} {{Automatic Taxobox | fossil_range = Ediacaran {{fossil range|560}} | image = Spriggina_floundersi_-_MUSE.jpg | image_caption = A reconstruction of the type species, ''Spriggina floundersi'' | taxon = Sprigginidae | authority = Glaessner, 1958<ref name=Glaessner1958/> | type_species = †''Spriggina floundersi'' | type_species_authority = Glaessner, 1958 | subdivision_ranks = Genera | subdivision = See text }}

'''Sprigginidae''' is an extinct family of the class Cephalozoa, characterized by having a greater number of isomers than its sister taxon, Yorgiidae. They lived approximately 635 million years ago, in the Ediacaran period.

== Description == Like most members of Proarticulata, their body plan consists of isomers arranged in glide symmetry, meaning they do not have true bilateral symmetry, although what sets them out from other proarticulates is their greater number of isomers, numbering up to around 40, sometimes more, overall. In most cases, they also have a distinct horseshoe-shaped 'head'.<ref name=Glaessner1958/>

When the first member of the family, ''Spriggina'', was discovered, it was considered to be a polychaete annelid,<ref name=Glaessner1958/> a petalonamid frond, and even an arthropod, with probable relations to trilobites.<ref>{{cite book |last1=Sokolov |first1=B |last2=Iwanowski |first2=A |title=The Vendian System |date=1985 |publisher=Springer Berlin |url=https://link.springer.com/book/9783642739743 |language=en}}</ref> Although most recent studies now agree that ''Spriggina'', and the family it is a part of, are part of the phylum Proarticulata.<ref name=Ivantsov2004>{{cite journal|last=Ivantsov|first=A.Yu|year=2004|title=New Proarticulata from the Vendian of the Arkhangel'sk region|journal=Paleontological Journal|volume=38|issue=3|pages=247–253|url=http://vend.paleo.ru/pub/Ivantsov_2004_eng.pdf|access-date=2007-09-27|url-status=dead|archive-url=https://web.archive.org/web/20070927022709/http://vend.paleo.ru/pub/Ivantsov_2004_eng.pdf|archive-date=2007-09-27}}</ref>

==Distribution== Most genera are restricted to sediments within the Flinders Ranges of South Australia,<ref name=Glaessner1958>{{Cite journal|author=Glaessner, Martin F.|year=1958|url=http://www.samuseum.sa.gov.au/Journals/TRSSA/TRSSA_V081/TRSSA_V081_p185p188.pdf|title=New Fossils from the Base of the Cambrian in South Australia|journal=Transactions of the Royal Society of South Australia|volume=81|pages=185–188|id={{BHL page|41001421}}|archive-url=https://web.archive.org/web/20070929094012/http://www.samuseum.sa.gov.au/Journals/TRSSA/TRSSA_V081/TRSSA_V081_p185p188.pdf|archive-date=29 September 2007}}</ref> although some can be found within the Ust' Pinega Formation of Russia.<ref name=Ivantsov2004/>

==Taxonomy== Sprigginidae includes the following genera:

*† ''Spriggina'' Glaessner, 1958 **† ''Spriggina floundersi'' Glaessner, 1958 *† ''Marywadea'' Glaessner & Wade, 1966 **† ''Marywadea ovata'' Glaessner & Wade, 1966 *† ''Cyanorus'' Ivantsov, 2004 **† ''Cyanorus singularis'' Ivantsov, 2004 *† ''Praecambridium'' (?) Ivantsov, 1999 **† ''Praecambridium sigillum'' (?) Ivantsov, 1999

Due to the rather small size of known ''Praecambridium'' specimens, and the large grain size of the matrix they are commonly found in, the placement of ''Praecambridium'' within the Sprigginidae family is tentative, as it is hard to discern certain details in such small specimens, but are placed within Sprigginidae based on a recent study that suggested they may be juvenile forms, if not of ''Spriggina'' itself, which has been found within the same beds of ''Praecambridium''.<ref>{{cite journal |last1=Ivantsov |first1=A. Yu. |title=Small Vendian transversely Articulated fossils |journal=Paleontological Journal |date=April 2007 |volume=41 |issue=2 |pages=113–122 |doi=10.1134/S0031030107020013|bibcode=2007PalJ...41..113I }}</ref> Although other studies have noted that most reconstructions show similarities with juvenile forms of ''Yorgia'', with it possibly being a larval stage of ''Yorgia'' itself.<ref name=Ivantsov2001>{{cite journal |author= Ivantsov, A.Y. |year= 2001 |title= ''Vendia'' and Other Precambrian "Arthropods" |journal= Paleontological Journal |volume= 35 |issue= 4 |pages= 335–343 |url= https://www.academia.edu/2605872}}</ref>

''Metaspriggina'' was previously tentatively assigned to Sprigginidae, even deriving its generic name from ''Spriggina'',<ref>{{cite journal |last1=Simonetta |first1=Alberto M. |last2=Insom |first2=Emilio |title=New animals from the Burgess Shale (Middle Cambrian) and their possible significance for the understanding of the Bilateria |journal=Bolletino di Zoologia |date=January 1993 |volume=60 |issue=1 |pages=97–107 |doi=10.1080/11250009309355797}}</ref> although a more recent study redescribing the genus saw it re-assigned within the phylum Chordata.<ref>{{cite journal |last1=Morris |first1=Simon Conway |title=A redescription of a rare chordate, Metaspriggina Walcotti Simonetta and Insom, from the Burgess Shale (Middle Cambrian), British Columbia, Canada |journal=Journal of Paleontology |date=March 2008 |volume=82 |issue=2 |pages=424–430 |doi=10.1666/06-130.1|bibcode=2008JPal...82..424M }}</ref>

==Gallery== <gallery> Spriggina_flounensi_C.jpg | ''Spriggina floundersi'' Cyanorus_singularis.jpg | ''Cyanorus singularis'' Praecambridium sigillum restoration.jpg | ''Praecambridium sigillum'' </gallery>

==See also== *Cephalozoa *Yorgiidae

==References== {{Reflist}}

Category:Sprigginidae Category:Ediacaran life