Late Cambrian, Early Ordovician – Late Triassic
Murchisoniina is an extinct order of facultatively mobile, epifaunal suspension feeders
Characteristics of the Order
- High-spired shell with numerous whorls
- Submedian sinus in outer lip, may culminate in a slit or notch
- Inner shell layers seemingly not nacreous
Treatise on Invertebrate Paleontology, Part I, Mollusca 1 (1960):
- Shell commonly high-spired, with numerous whorls; outer lip with submedian sinus which may culminate in slit or notch and which was presumably exhalant in function; inner shell layers seemingly not nacreous; some genera with incipient abapical apertural canal; paired ctenidia are inferred to have been present by analogy with the Pleurotomariina, but if the abapical canal was inhalant in function, the respiratory system may have undergone evolutionary advances beyond the condition characteristic of that suborder.