Fig. 1. Development of chamberlet cycles from an auxiliary chamber in an early orbitoid, the Campanian Lepidorbitoides minima H. Douvillé from Mexico, after Aguilar et alii, 2002. A: stereograph of a megalospheric embryo consisting of a biconch (protoconch and deuteroconch) supplemented by a third chamber (auxiliary chamber) with a median and two lateral stolons. Successive growth stages coloured alternately in red and blue. Lamellation omitted. Schematic, not to scale. B: development of chamberlet cycles. Schema, not to scale. Inner lamella omitted, outer lamella alternating in white or plain black in successive growth stages. Axes of successive stolons form overcrossing spirals (arrows). Median stolons indicated by dotted arrows, lateral stolons by black arrows. C: Camera lucida drawing of a slightly oblique section of the equatorial main chamberlet layer of adult growth stage showing retrovert apertures and annular passages. D: stereograph of adult chamberlets of two successive cycles with their crosswise-oblique stolon axes, the annular passage and their retrovert stolons. Schematic, not to scale. A: auxiliary chamber; D: deuteroconch; P: protoconch; X: closing chamberlet filling up the first chamberlet annulus; ap: annular passage; chl: chamber lumen; lst: lateral stolon; mst: median stolon; p: pores; rst: retrovert stolons; stax: crosswise-oblique stolon axes; (Hottinger, 2006; fig. 36  CC/BY-NC-SA)
- according to Hottinger (2006):
RETRAL STOLON - (retrovert stolon); in orbitoidiform foraminifera a stolon connecting main chamberlet lumina with lateral chamberlets. It is positioned in the median plane of the chamberlet parallel to the shell axis and is directed backwards, feeding the lateral chamberlets corresponding to its cycle.
Aguilar, Bernaus, Caus E. & Hottinger (2002), Lepidorbitoides minima Douvillé from Mexico, a foraminiferal index fossil for the Campanian, Journal of foraminiferal Research, Lawrence, vol. 32, N° 2, p. 126–134.
Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744
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