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Yorkicystis is a genus of edrioasteroid echinoderm that lived 510 million years ago in the Cambrian aged Kinzers Formation in what is now Pennsylvania. [1] This genus is important as it provides some of the oldest evidence of echinoderms losing their hard mineralized outer skeletons. [1]
The Eocrinoidea were an extinct class of echinoderms that lived between the Early Cambrian and Late Silurian periods. They are the earliest known group of stalked, brachiole-bearing echinoderms, and were the most common echinoderms during the Cambrian. The earliest genera had a short holdfast and irregularly structured plates. Later forms had a ...
Echinoid fossils are sometimes found associated with archaeological sites. The earliest known example in England is an Acheulean hand axe from the Middle Pleistocene found in Kent. The craftsman had evidently chosen to use this flint for his tool; the exposed area around the sea urchin's jaws known as Aristotle's lantern are clearly visible.
The oldest undisputed fossils of Edrioasteroidea are known from Cambrian (Stage 3, about 515-520 Ma ago) of Laurentia and are among the oldest known fossils of echinoderms. Some authors propose that an enigmatic Ediacaran (about 600 Ma) organism Arkarua is also an edrioasteroid, but this interpretation did not gain wide acceptance. [ 3 ]
Ctenocystoids were widespread during the Middle Cambrian, and have been found in the United States, the United Kingdom, Australia, France, the Czech Republic, Poland, Spain, and Morocco. [11] The earliest ctenocystoids date to the beginning of Stage 5 of the Cambrian, [ 12 ] now known as the Wuliuan age, [ 13 ] or possibly slightly earlier, in ...
The three oldest known candidate echinoderms all lack stereom and other echinoderm apomorphies, making their inclusion in the phylum controversial. [145] Arkarua adami illustration by Pennetta. The oldest potential echinoderm fossil is Arkarua from the late Ediacaran of Australia circa 555 Ma. These fossils are disc-like, with radial ridges on ...
Helicoplacus (often misspelled Helioplacus) is the earliest well-studied fossil echinoderm. Fossil plates are known from several regions. Complete specimens were found in Lower Cambrian strata of the White Mountains of California. The animal was a cigar-shaped creature up to 7 centimetres (2.8 in) long that stood upright on one end.
This list excludes purely vernacular terms. It includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomina dubia), or were not formally published (nomina nuda), as well as junior synonyms of more established names, and genera that are no longer considered echinoderms. The list includes thousands of ...