Grypoceratidae
| Grypoceratidae Temporal range: L Carb (Miss) - UTriass |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Nautiloidea |
| Order: | Nautilida |
| Superfamily: | Trigonocerataceae |
| Family: |
Grypoceratidae Hyatt in Zittle (1900) |
Grypoceratidae is the longest-lived family of the Trigonocerataceae, or of the near equivalent Centroceratina; members of the Nautilida from the Upper Paleozoic and Triassic.(Kummel 1964)
The Grypoceratidae are characterized by evolute to involute shells that may have some modification to the venter (the outer rim) varying from flattened to subangular, or bearing a keel. Most are smooth but some have nodes or carinae (auxiliary keels). Sutures generally have distinct ventral and lateral lobes but in some, a ventral saddle. Whorl sections are generally compressed but may be subquadrate to subtrapizoidal or coronate (heart shaped), or slightly depressed dorso-ventrally. (Flower 1950, Kummel 1964)
The Grypoceratidae begin with Epidomatodceras from the Lower Carboniferous (Mississippian), an evolute form with a smooth shell, subquadrate whorl section, and a sharp angular ventral lobe in the suture. Epidomatoceras is followed by Domatoceras, Paradomatoceras, Stearoceras, Stenopoceras, and Titanoceras from the Upper Carboniferous (Pennsylvanian) and Lower Permian.
Domatoceras, Paradomatoceras, and Titanoceras are rather similar in that they are somewhat large, evolute with whorls in contact but not deeply impressed along the inner margin of the whorls, and with straight flanks and flattened venters. Whorl sections vary from strongly compressed side to side with height much greater than width in Paradomatoceras to slightly depressed with height less than width in Titanoceras, with Domatoceras subquadrate in between.
Stearoceras is involute with a depressed subtrapizoidal whorl section and slight ventral and lateral lobes. Stenoporceras is subdiscoidal, flattened laterally, and has a suture with broad lateral lobes and a deep ventral saddle as found in syringonautilids.
Permian genera include Parastenopoceras, a smooth, involute form with a semiellptical whorl section and ventral saddle; Plummeroceras, a form similar to Domatoceras but more evolute and with a deep ventral lobe; Pselioceras, a smooth evolute form with a perforate umbilicus, ovoid whorl section, and suture crossing straight over the venter; and Virgaloceras, also similar to Domatoceras but with a row of nodes on the umbilical wall and a ventral saddle instead of the ventral lobe in the suture. Parastenopoceras, Plummeroceras, and Pselioceras are from the Lower Permian; Virgaloceras is from the Upper Permian.
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