"[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.

[6] Some fossils have what may be a circular mouth at the centre of the semicircular head, although interpretation is hampered by the small size of the creature relative to the large grains of sandstones in which it is preserved.

The symmetry observed is not exactly bilaterian[6] but appears to be a glide reflection, where opposite segments are shifted by half an interval.

[citation needed] The genus was named after Reg Sprigg who discovered the fossils of the Ediacara Hills—part of the Flinders Ranges in South Australia—and was a proponent of their recognition as multicellular organisms.

Fossils from the Vindhyan basin, reliably dated to around 1,650 million years old,[9] have been classified as Spriggina,[10] but in all likelihood represent microbial artifacts.

[9] Spriggina possessed a tough, though uncalcified body, evident from the fossils' preservation: always as a mould in the lower surface of the fossiliferous bed.

It bears some similarity to the living polychaete worm Tomopteris and Amphinomidae,[11] but its lack of chaetae, along with other lines of evidence, suggests that it cannot be placed in this phylum.

[22] Furthermore, the broad pleural lobes of trilobites served primarily as a rigid hood under which the legs could process the sediment for food.