Middle Ordovician – Middle Permian
Trochonematidae is an extinct family of facultatively mobile epifaunal suspension feeders
Description of the Family
- Turbiniform shell
- Perforate or imperforate
- Surface of shell exhibits several strong revolving ridges or numerous spiral striae
- Shell has nacreous lining
Treatise on Invertebrate Paleontology, Part I (1960) (Same as Superfamily Trochonematacea):
- Turbiniform, with channel at labrum within a spiral angulation about midway between sutures or higher on whorl, or with shallow sinus at about the same position; ornament spiral angulations, threads or cords, or rows of nodes, with collabral threads or growth lines; shell with nacreous lining.
Ulrich & Scofield (1897):
- Shells trochoid, turbiniform or somewhat planorbiform, perforate or imperforate; margin of aperture entire, simple, rarely trumpet-shaped, sometimes with a wide angled notch and carina in the upper or outer part; no slit nor distinguishable band; surface with several strong revolving ridges or more numerous spiral striae; test very slightly or not at all nacreous. Operculum unknown, probably incapable of preservation.