Sprigginidae

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.

Sprigginidae Temporal range: Ediacaran 560 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
A reconstruction of the type species, Spriggina floundersi
Scientific classification
Kingdom:	Animalia
Phylum:	†Proarticulata
Class:	†Cephalozoa
Family:	†Sprigginidae Glaessner, 1958[1]
Type species
†Spriggina floundersi Glaessner, 1958
Genera
See text

Description

Like most members of Proarticulata, their body plan consists of isomers arranged in a 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. They also have a distinct 'horseshoe' shaped 'head'.^[1]

When the first member of the family, Spriggina, was discovered, it was considered to be a polychaete annelid,^[1] and petalonamid frond, and even an arthropod, with probable relations to trilobites.^[2] Although most recent studies now agree that Spriggina, and the family its apart of, are apart of the phylum Proarticulata.^[3]

Distribution

Most genera are restricted to sediments within the Flinders Ranges of South Australia,^[1] although some can be found within the Ust' Pinega Formation of Russia.^[3]

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 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.^[4] 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.^[5]

Metaspriggina was previously tentatively assigned to Sprigginidae, even deriving its generic name from Spriggina,^[6] although a more recent study redescribing the genus saw it re-assigned within the phylym Chordata.^[7]

Gallery

• 
  Spriggina floundersi
• 
  Cyanorus singularis
• 
  Praecambridium sigillum

See also

• Cephalozoa
• Yorgiidae