Namacalathus instance of fossil taxon
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 age from the fossiliferous rock in Namibia and Oman provides an age for the Namacalathus zone in the range from 549 to 542 Ma, which corresponds to the Late Ediacaran.
Alongside Namapoikia and Cloudina, these organisms are the oldest known evidence in the fossil record of the emergence of calcified skeletal formation in metazoans, a prominent feature in animals appearing later in the Early Cambrian. Shore et al. (2021) reported the first three-dimensional, pyritized preservation of soft tissue in Namacalathus hermanastes from the Nama Group (Namibia), and evaluate the implications of this finding for the knowledge of the phylogenetic relationships of this animal; they suggest it is an ancestor of Lophotrochozoan animals such as brachiopods and worms.There are only five occurrences of Namacalathus (Namibia, Canada, Oman, Siberia, Paraguay) known to date, all of which are found in association with Cloudina fossils.Among the late Precambrian fossil assemblage in the Nama group, Namibia, Namacalathus far outnumber Cloudina and other poorly preserved taxa and ichnofossils found in the formation. The Nama Group fossils occur within thrombolitic facies of immense Proterozoic stromatolitic reefs. Namacalathus lived a benthic existence with its stalk attached to the sea floor by means of a holdfast, or possibly to algal mats growing on the reef surface.
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