Editing Blastoid (section)

{{Short description|Extinct class of marine invertebrates}}
{{Distinguish|Blastoid (embryoid)}}
{{Automatic taxobox
| name = Blastoids
| fossil_range = {{fossilrange|Middle Ordovician|Permian|earliest=Middle Cambrian|[[Ordovician]] - [[Permian]]}}
| image = Fósil de erizo de mar (Pentremites godoni), Waterloo, Illinois, Estados Unidos, 2021-01-18, DD 081-136 FS.jpg
| image_caption = ''[[Pentremites|Pentremites godoni]]'', a blastoid from the Lower Carboniferous of Illinois.
| taxon = Blastoidea
| authority = [[Thomas Say|Say]], 1825
| subdivision_ranks = Orders
| subdivision =
[[Fissiculata]]<br />
[[Spiraculata]]
<br />
''Incertae sedis'':<br />
†''[[Macurdablastus]]''
}}

[[Image:Haeckel Blastoidea.jpg|thumb|right|200px|"Blastoidea", from [[Ernst Haeckel]]'s ''[[Kunstformen der Natur|Art Forms of Nature]]'', 1904]]

'''Blastoids''' (class Blastoidea) are an [[extinct]] type of stemmed [[echinoderm]], often referred to as sea buds.<ref>{{cite book |author= Barnes, Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA|page= 1010|isbn= 0-03-056747-5}}</ref> They first appear, along with many other echinoderm classes, in the [[Ordovician]] period, and reached their greatest diversity in the [[Mississippian age|Mississippian]] subperiod of the [[Carboniferous]] period. However, blastoids may have originated in the [[Cambrian]]. Blastoids persisted until their [[extinction]] at the [[Permian-Triassic extinction event|end]] of [[Permian]], about 250 million years ago. Although never as diverse as their contemporary relatives, the [[crinoid]]s, blastoids are common fossils, especially in many Mississippian-age rocks.