Acta Palaeontologica Polonica

Structure and mode of origin of the ammonite proseptum

Cyprian Kulicki

Acta Palaeontologica Polonica 20 (4), 1975: 535-542

Results of studies of the structure and the relation of proseptum to the shell walls are presented. Proseptum develops in a deepening furrow extending around the posterior body part, simultaneously with the internal prismatic lamina of the initial chamber and the first whorl. Prosiphon and caecum appear later than proseptum. The proseptum is an extraordinary element dissimilar to subsequent septa.

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