Sprigginidae is an extinct family of the class

Cephalozoa Cephalozoa are an extinct class (biology), class of primitive segmented marine organisms within the Phylum (biology), Phylum Proarticulata from the Ediacaran period. They possessed bilateral symmetry and were characterized by a thin, rounded body ...

, characterized by having a greater number of

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the existence or possibili ...

than its sister taxon,

Yorgiidae Yorgiidae is an extinct family of the class Cephalozoa, which is a part of the wider phylum Proarticulata. They lived from around 571 to 551 Ma. Description Like other relatives within the phylum Proarticulata, their body plan consists of is ...

. 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 a

glide symmetry In geometry, a glide reflection or transflection is a geometric transformation that consists of a reflection across a hyperplane and a translation ("glide") in a direction parallel to that hyperplane, combined into a single transformation. Bec ...

, meaning they do not have true

bilateral symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symme ...

, although what sets them out from other proarticulates is their greater number of isomers, numbering up to around 40, sometimes more, overall. They also have a distinct 'horseshoe' shaped 'head'. When the first member of the family, ''

Spriggina ''Spriggina'' is a genus of early animals whose relationship to living animals is unclear. Fossils of ''Spriggina'' are known from the late Ediacaran period in what is now South Australia. ''Spriggina floundersi'' is the official fossil emblem o ...

'', was discovered, it was considered to be a

polychaete Polychaeta () is a paraphyletic class of generally marine Annelid, annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called c ...

annelid, and petalonamid frond, and even an

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

, with probable relations to

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

. Although most recent studies now agree that ''Spriggina'', and the family its apart of, are apart of the phylum Proarticulata.

Distribution

Most genera are restricted to sediments within the

Flinders Ranges The Flinders Ranges are the largest mountain ranges in South Australia, which starts about north of Adelaide. The ranges stretch for over from Port Pirie to Lake Callabonna. The Adnyamathanha people are the Aboriginal group who have inhab ...

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...

, although some can be found within the Ust' Pinega Formation of

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

Taxonomy

Sprigginidae includes the following genera: *† ''

'' 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 ''Praecambridium sigillum'' is an extinct organism that superficially resembles a segmented trilobite-like arthropod. It was originally described as being a trilobite-like arthropod, though the majority of experts now place it within the Proartic ...

'' (?) 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 its 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''. Although other studies have noted that most reconstructions show similarities with juvenile forms of ''

Yorgia ''Yorgia waggoneri'' is a discoid Ediacaran organism. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of . It is classified within the extinct animal phylum Proart ...

'', with it possibly being a larval stage of ''Yorgia'' itself. ''

Metaspriggina ''Metaspriggina'' is a genus of chordate initially known from two specimens in the Middle Cambrian Burgess Shale and 44 specimens found in 2012 at the Marble Canyon bed in Kootenay National Park. Whilst named after the Ediacaran organi ...

'' was previously tentatively assigned to Sprigginidae, even deriving its generic name from ''Spriggina'', although a more recent study redescribing the genus saw it re-assigned within the phylym

Chordata A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (Apomorphy and synapomorphy, synapomorphies) th ...

Gallery

Spriggina_flounensi_C.jpg , ''Spriggina floundersi'' Cyanorus_singularis.jpg , ''Cyanorus singularis'' Praecambridium sigillum restoration.jpg , ''Praecambridium sigillum''

References

{{Taxonbar, from=Q107123108 Ediacaran life

Description

Distribution

Taxonomy

Gallery

See also

References