Holdfasts of<i>Sphenothallus</i>(Cnidaria) from the early Silurian of western North Greenland (Laurentia)

Well-preserved holdfasts and early growth stages of the tubular cnidarian Sphenothallus are described from Silurian (Llandovery Series) Washington Land, North Greenland. The diameter holdfast is determined by formation a basal disc attached to substrate, upon which initially conical, but subsequently shell formed. characteristic opposing longitudinal thickenings developed at each angular margin as circular tube acquires an elliptical form.