Order Lychniscosida Schrammen, 1903

Abstract

Recent Lychniscosida Schrammen (Hexactinellida, Hexasterophora), which includes a once diverse and dominant group of fossils from Cretaceous benthic communities, now contains only two families and three genera as Recent members. The group is characterized by formation of a rigid dictyonal framework by fusion of lychniscid hexactins mainly by fusion of rays of adjacent dictyonalia arranged side- by-side – a euretoid pattern of junction. The length of rays which form the sides of dictyonal meshes is strictly limited to one mesh width, usually 150–400m. The constituent families are differentiated by thickness of structural units (walls, pillars, plates) and organization of dictyonalia – either in ranks or without detectable alignments. Structural units (tubule walls, pillars) are unchannelized, but it is possible to interpret the fine wall tubules of Diapleuridae as schizorhyses