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Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm, often referred to as sea buds. [1] They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. However, blastoids may have originated in the Cambrian.
Cryptoblastus is a genus of extinct blastoids, a primitive group of echinoderms related to the modern sea lilies. [1] Fossils are found in sedimentary rocks laid down in the Early Carboniferous period some 360 to 320 million years ago.
These stalked echinoderms averaged a height of about 11 centimetres (4.3 in) but occasionally ranged up to about 3 times that size. They, like other blastoids, superficially resemble their distant relatives, the crinoids or sea lilies, having a near-identical, planktivorous lifestyle living on the sea floor attached by a stalk.
It is often considered to be the second-largest known extinction event just behind the end-Permian mass extinction, in terms of the percentage of genera that became extinct. [ 2 ] [ 3 ] Extinction was global during this interval, eliminating 49–60% of marine genera and nearly 85% of marine species. [ 4 ]
Eight of the extinct bird species were found in Hawaii, including the Po`ouli, which was last seen in 2004. The Po`ouli is the most recently seen species of all 21 animals on the list.
The earliest phase of the seaway began in the mid-Cretaceous when an arm of the Arctic Ocean transgressed south over western North America; this formed the Mowry Sea, so named for the Mowry Shale, an organic-rich rock formation. [1] In the south, the Gulf of Mexico was originally an extension of the Tethys Ocean. In time, the southern embayment ...
Species go extinct constantly as environments change, as organisms compete for environmental niches, and as genetic mutation leads to the rise of new species from older ones. At long irregular intervals, Earth's biosphere suffers a catastrophic die-off, a mass extinction , [ 9 ] often comprising an accumulation of smaller extinction events over ...
But today, my neighborhood just north of Washington, D.C., stands out as highly countercultural — an island of fertility in an ever-widening sea of infertility sweeping the world. This natalism ...