Spyroceratidae
| Spyroceratidae | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | †Pseudorthocerida |
| Family: | †Spyroceratidae Shimazu & Obata 1935 |
Spyroceratidae are defined 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.