Sphenothallus

Sphenothallus is a problematic extinct genus lately attributed to the conulariids. It was widespread in shallow marine environments during the Paleozoic.^[2][4]

Sphenothallus Temporal range: Upper Lower Cambrian–Mississippian[Note 1][1][2][3] PreꞒ Ꞓ O S D C P T J K Pg N
Sphenothallus holdfast from the Kope Formation (Upper Ordovician), Gunpowder Creek, Kentucky.
Scientific classification
Kingdom:	Animalia
Phylum:	Cnidaria
Order:	†Conulatae
Clade:	†Conulariida
Genus:	†Sphenothallus Hall, 1847

Occurrence

Sphenothallus is represented in the Cambrian period in the Kaili biota and the Mount Stephen trilobite beds, where it co-occurs with the similar organisms Cambrorhythium and Byronia.^[1] It is known in younger strata in Canada and the US, surviving at least until the Mississippian.^[3]

Ecology

Sphenothallus lived in groups as an opportunist in environments from hardgrounds to soft mud, even if depleted in oxygen.^[3] It probably dispersed via larvae.^[3]

Notes

1. Earliest, upper Lower Cambrian (Van Iten et al 2002); latest, not referenced; at least to Mississippian