Fig. 1. Feathered grooves. All specimens figured as SEM graphs. A-B: Ammonia beccarii (Linné), Adriatic Sea, Recent. Peripheral and oblique - umbilical views. Note the ridges on the apertural face that initiate the feathering when the next chamber is added during ontogeny. C-D: Neorotalia calcar (d'Orbigny), Keij Island, Indonesia. Recent. Ventral view of an entire specimen and detail of a ventral feathered groove covered by a folded outer lamella. Note the imperforate nature of the cover and the orifices of the canal system. Compare: enveloping canals. E-G: Unfeathered grooves in Ammonia ikebei (Inoue et Nakaseko), Eastern Kalimantan, Borneo, Upper Miocene. Peripheral view of entire specimen and details in oblique-umbilical and in dorsal views. Note the hemicircular attachment of the septal flap and the undivided umbilical plug that correspond to unfeathered septal grooves; af: apertural face; f: foramen; fea: feathered grooves; ol: (folded) outer lamella covering a septal groove that is converted to an interlocular space; or: canal orifice; pil: pile; s: septum; sgr; septal groove (unfeathered); spgr: spiral groove (unfeathered); upl: umbilical plug; (Hottinger, 2006; fig. 50) CC/BY-NC-SA)
- according to Hottinger (2006):
FEATHERED - ornamented by numerous parallel grooves extending in more or less perpendicular direction from sutural furrow or fissure onto shoulders of ventral chamber walls, as in many rotaliids.
Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744
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