Spriggina is a genus of early bilaterian 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 of South Australia;[2] it has been found nowhere else.
The organism reached 3–5 centimetres (1.2–2.0 in) in length and may have been predatory. Its bottom was covered with two rows of tough interlocking plates, while one row covered its top; its front few segments fused to form a "head."[citation needed]
The affinity of Spriggina is unknown; it has been variously classified as an annelid worm, a rangeomorph-like frond, a variant of Charniodiscus, a proarticulatan, an arthropod (perhaps related to the trilobites), or even an extinct phylum. The lack of known segmented legs or limbs, coupled with the presence of glide reflection instead of symmetric segments, suggests that an arthropod classification is unlikely despite some superficial resemblance.[3]
The genus Spriggina originally contained three different species—S. floundersi, S. ovata, and S. borealis—but S. ovata is now considered a junior synonym of Marywadea ovata,[4][5] while the phylogenetic status of S. borealis remains[as of?] a subject of debate.[5]
Spriggina grew to 3–5 centimetres (1.2–2.0 in) in length and was approximately oblong. The organism was segmented, with no fused segments; the segments were sometimes curved.[6] The upper surface of the organism was covered by one row of overlapping cuticular plates, the underside with paired plates.[6]
The first two segments formed a "head". The front segment had the shape of a horseshoe with a pair of depressions on its upper surface; these may have represented eyes.[6] The second segment may have borne antennae. Subsequent segments bore annulations.[6]