Arenactinia
{{Short description|Genus of sea anemones}}
{{Taxobox
| name = Arenactinia
| image = Parnaíba Basin.png
| image_caption = Parnaíba Basin
| regnum = Animalia
| phylum = Cnidaria
| classis = Hexacorallia
| ordo = Actiniaria
| genus = Arenactinia
| species = Arenactinia ipuensis
}}
Arenactinia is a genus of sea anemone that lived in Brazil during the early Silurian period. Its early apperence suggest that this genus may be related to the adaptive radiation of marine ecosystems following the Late Ordovician Extinction. This genus contains one species, Arenactinia ipuensis.{{Cite journal |last=Barroso |first=Francisco Rony Gomes |last2=Viana |first2=Maria Somália Sales |last3=Agostinho |first3=Sonia |last4=Daly |first4=Marymegan |last5=Fairchild |first5=Thomas Rich |last6=Marques |first6=Antonio Carlos |last7=Pacheco |first7=Mírian Liza Alves Forancelli |date=2025-03-01 |title=Insights into the lifestyle and preservation of Arenactinia ipuensis n. gen. et n. sp. (Anthozoa, Actiniaria) from the Early Silurian (Ipu Formation, Parnaíba Basin, Brazil) |url=https://www.sciencedirect.com/science/article/pii/S2950475925000012 |journal=Earth History and Biodiversity |volume=3 |pages=100017 |doi=10.1016/j.hisbio.2025.100017 |issn=2950-4759}}
It was discovered in South America in the Ipu formation in the Parnaiba Basin of Brazil.
Description
The body shapes of Arenactina can be discoidal, conical, cylindrical, flattened or bipartite. The body is divided into a cylindrical column and a exspanded base. This species processes a oral disk with discrete tentacles. This gives Arenactina a simular body shape to modern sea anemone that burrow into soft substrates.