Spyroceratidae
From Infogalactic: the planetary knowledge core
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Spyroceratidae
Shimazu & Obata 1935
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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.
References
- Sweet, Walter C. 1964. Nautiloidea -Orthocerida. Treatise on Invertebrate Paleontology, Part K. Geological Soc. of America and Univ of Kansas press.
