Spriggina floundersi is an extinct segmented organism from the Ediacaran period (635 - 542 Mya). It grew up to 60mm in length and was one of the earliest complex multi-cellular organisms to appear on Earth. It has become one of the most keenly studied organisms from this period.
Spriggina is of great interest to palaeontology because it appears to combine a number of key evolutionary traits. These include: bilateral symmetry, a "head" and a "tail", motility, the suggestion of a mouth and digestive tract and possible light sensitive buds on its horseshoe shaped head - which has similarities to the trilobite cephalon. So was it a stem-arthropod?
Spriggina was first classified as an annelid (Glaessner, 1957), because of its worm like segmentation but later analysis suggests that Spriggina may be more closely related to the arthropoda phylum and possibly the trilobita class (McMenamin, 2003). This has been countered by other analysis that points to Spriggina having a glide-reflection morphology rather than bilateral symmetry - precluding it from the arthropod phylum - although this discrepancy has been attributed to taphonomic processes or distortions incurred during fossilisation.
Spriginna fossils of the Ediacaran period tend to lie within relatively coarse matrixes so impressions lack precise detail, making it hard to draw conclusive observations. The debate on taxonomic classification continues.
Spriggina was discovered by Reg Sprigg in the1940's within the Ediacaran Hills of the Flinders Ranges of South Australia and it became the state fossil emblem of South Australia in 2017.
With thanks to Prof. Jim Gehling for feedback on anatomical detail.
