Aspidella

Genus of Ediacaran animals
Aspidella is also a homonym for the mushroom genus Saproamanita. Aspidella is an Ediacaran disk shaped fossil of uncertain affinity. It is known from the single species A. terranovica. Most individuals are between 4 and 10 mm, but smaller individuals would presumably have decayed before they could fossilize. Other Aspidella take the form of ellipses, 3–8 cm long and 1–4 cm wide. Most have a central pimple. The rim of all specimens is made up by ridge edged rays and/or concentric rings.

The rarity of large individuals probably indicates that Aspidella were r strategists, producing numerous offspring of which most died young. It is most common in deep water sediments, but is a constituent of most Ediacaran fossil assemblages, including those deposited above storm wave base. whereas others represent microbial colonies. Some individuals are associated with movement trails resembling those produced by modern sea anemones (Cnidaria).

The upper and lower surfaces of the fossils have a distinct elemental composition that resembles that of fossilized biofilms. The sediment within the fossils also has a distinct composition, being enriched in certain elements with respect to the rock matrix. Since it is difficult to account for such a distribution of elements by post mortem diagenetic processes, it would appear that the elements (and thus the sediment) were incorporated into the organism whilst it was alive. In 1872, Elkanah Billings described Aspidella terranovica fossils from Duckworth Street, St. John's, Newfoundland They are preserved in a Neoproterozoic outcrop of black shale. Billings was the head paleontologist with the Geological Survey of Canada at the time. Even so, his findings were questioned by Charles Doolittle Walcott, who quoted opinion that the shapes in the rocks were concretions formed inorganically. Other explanations offered at the time were that the circles were gas escape bubbles, or fakes planted by God to lure those with little faith into error. They were the first Ediacaran (Vendian) fossils described by a scientist. For decades, Aspidella and its partner fossils were not considered to be Precambrian life forms. This lasted until the work of Reg Sprigg, who discovered the Ediacara Hills fossils. Fossils were found in many other parts of the world in rocks of about the same age and became accepted as genuine remains of life forms.

Other locations where Aspidella specimens are reported include the Bonavista Peninsula and Mistaken Point in Newfoundland, the Twitya Formation in British Columbia, and central North Carolina. Aspidella fossils are found from , with putative representatives dating to
More recently, Aspidella fossils have been found in the mid Tonian aged Heavitree Formation, Amadeus Basin, Central Australia, dated to ~ .