''Namapoikia rietoogensis'' is among the earliest known animals to produce a

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an ad ...

(probably

aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...

) skeleton. Known from the Ediacaran period, before the Cambrian explosion of calcifying animals, the long-lived organism grew up to a metre in diameter and resembles a colonial

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

. It was an encruster, filling vertical fissures in the

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...

s in which it originally grew. The fossil was first found in the Omkyk Member of the

Nama Group The Nama Group is a megaregional Vendian to Cambrian group of stratigraphic sequences deposited in the Nama foreland basin in central and southern Namibia. The Nama Basin is a peripheral foreland basin, and the Nama Group was deposited in two e ...

from Rietoog in southern

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

, in association with other calcifying fossils, '' Cloudina'' and ''

Namacalathus ''Namacalathus'' is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, ''N. hermanastes'', was first described in 2000 from the Nama Group of central and southern Namibia. A U–Pb zircon ag ...

''. Its mineralogy and accretionary style has been compared with that of the Lophotrochozoans, though its unfamiliar morphology suggests a stem-group or deeper affiliation to this group. It grew in spurts, first emplacing an organic skeleton, then filling this in with aragonite.

References

Ediacaran life Enigmatic prehistoric animal genera Precambrian Africa Fossils of Namibia Fossil taxa described in 2002 {{Precambrian-animal-stub

See also

References