Polycystine

Polycystine
Skeleton of a polycystine
Scientific classification
Domain:	Eukaryota
Clade:	Diaphoretickes
Clade:	SAR
Phylum:	Retaria
Subphylum:	Radiolaria
Class:	Polycystina Ehrenberg, 1838, emend. Haeckel, 1887
Orders[1]
Collodaria Nassellaria Spumellaria

This article relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. Find sources: "Polycystine" – news · newspapers · books · scholar · JSTOR (February 2022)

The polycystines are a group of radiolarians. They include the vast majority of the fossil radiolaria, as their skeletons are abundant in marine sediments, making them one of the most common groups of microfossils. These skeletons are composed of opaline silica. In some it takes the form of relatively simple spicules, but in others it forms more elaborate lattices, such as concentric spheres with radial spines or sequences of conical chambers. Two of the orders belonging to this group are the radially-symmetrical Spumellaria, dating back to the late Cambrian period, and the bilaterally-symmetrical Nasselaria, whose origin is placed within the lower Devonian.^[2]