[3] Archaic Cambrian-style siphonotretids such as Schizambon and Helmersenia, with basic forms of ornamentation, populated the shores of Baltica, Laurentia, and Gondwana by the start of the Ordovician.

In the late Tremadocian, advanced Ordovician-style spiny siphonotretids spread out from temperate waters around Gondwana and mostly replaced their older relatives.

[8] Similar to acrotretides, the pedicle foramen was set at the apex of the ventral valve, though it is often elongated into a tubular groove opening forwards.

[1] The possible siphonotretid Acanthotretella is known from several exceptionally-preserved specimens which reveal lingulid-like traits such as setae, a spirolophous lophophore and U-shaped gut.

Combined with a lightweight shell, the pedicle likely helped to suspend the body above the seabed, an epibenthic lifestyle dissimilar to the infaunal (burrowing) lingulids.