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CloudinidCloudinids (Cloudinia) are an extinct animal phylum that formed small tubelike or conical fossils consisting of "cup-in-cup" segments of calcareous material. What the animal itself looked like is still unknown. Cloudinids were widely distributed. They are quite abundant in some deposits. They are the earliest common animal form with a calcareous shell. The name Cloudinia honors 20th Century geologist and paleontologist Preston Cloud. Cloudinia are characteristic of the so-called 'Small Shelly Fauna' in the final Neoproterozoic period, called the Tommotian, and disappeared in the extinction event that marks the Cambrian boundary, most recently dated 542mya. The extinctions (which didn't affect microbes, however) are connected with the worldwide glaciation often referred to as 'Snowball Earth' and set the stage for the Cambrian explosion of life-forms.
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