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 of South Australia; 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."

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 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, while the phylogenetic status of S. borealis remains a subject of active debate.

Description

Spriggina was a small, early animal that lived a very long time ago. It grew to be about 3 to 5 centimeters long, which is roughly the size of a small pencil. Its body was made up of many parts, or segments, that looked a bit like rings.

On its back, Spriggina had overlapping plates, and on its belly, it had paired plates. The first two parts of its body formed what we might call a “head.” The very front part looked like a horseshoe and might have had something like eyes. The next part may have had something like antennae. We do not know much about its mouth or legs because they were not preserved in the fossils.

Discovery and naming

The genus was named after Reg Sprigg, who found the fossils of the Ediacara Hills in the Flinders Ranges in South Australia. He believed these fossils were from living, many-celled organisms. Spriggina floundersi is the only widely accepted species in this genus. The name "floundersi" honors Ben Flounders, an amateur fossil hunter from South Australia. Another type, Spriggina ovata, is now placed in a different group called Marywadea.

Spriggina fossils come from a very old time called the Ediacaran period. Some fossils from the Vindhyan basin, about 1,650 million years old, were thought to be Spriggina, but they are likely just natural shapes made by tiny living things.

Spriggina had a strong body that did not turn to stone, which we can see from the way the fossils were formed.

Classification

The relationship of Spriggina to living animals is still unclear. It looks a bit like some modern worms, but it does not have certain features that would put it in that group. Some scientists have thought it might be related to an animal group called arthropods, which includes insects and spiders, because of its shape. However, newer studies show that Spriggina does not share enough special traits with arthropods to say for sure that it is one. This means its true place among living things remains a mystery.

Affinity

Scientists first thought Spriggina looked like a type of worm called Nereis. But when they looked closer, they saw the parts of its body didn't match up perfectly, similar to another ancient creature called Dickinsonia. In 1989, a scientist named Seilacher suggested Spriggina might actually be like a sea-pen, with what looks like a "head" being more like a base to hold it down.

Some people also thought Spriggina might be related to arthropods because it looked a little like a trilobite from the Cambrian time. But Spriggina didn’t have limbs or an exoskeleton, which made this idea less likely. Trilobites had special parts to help them move and find food, which Spriggina did not have.

South Australia’s fossil emblem

On February 14, 2017, Spriggina became the official fossil emblem of South Australia. This is because Spriggina has only ever been found in that area. The fossil, which is about 550 million years old, was chosen in an online vote where over 3,500 people from South Australia participated. It was selected to represent the state's important geological and scientific history.