| Spyroceratidae Temporal range: M Silurian - Permian |
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|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Nautiloidea |
| Superorder: | Orthoceratoidea |
| Order: | Pseudorthocerida |
| Family: | Spyroceratidae Shimazu & Obata 1935 |
Spyroceratidae are defined (Sweet, 1964, K246) as Pseudorthocerida with uniformly slender siphuncle segments, longer than wide, that contract sharply near either end, in which endosiphuncular deposits first form a compete annulus before fusing ventrally.