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Superfamilies: Orbitodacea, Spirillinacea, Duostominacea and Robertinacea

Superfamilies: Orbitodacea, Spirillinacea, Duostominacea and Robertinacea. Lecture 10. Superfamily Orbitodacea. The orbitoids are a Late Cretaceous to Miocene group of "larger foraminifera" which originated in tropical Americas.

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Superfamilies: Orbitodacea, Spirillinacea, Duostominacea and Robertinacea

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  1. Superfamilies: Orbitodacea, Spirillinacea, Duostominacea and Robertinacea Lecture 10

  2. Superfamily Orbitodacea • The orbitoids are a Late Cretaceous to Miocene group of "larger foraminifera" which originated in tropical Americas. • Their tests are radial hyaline and perforate, with a discoidal mode of growth, the chambers being arranged in annular cycles rather than plane spirals. • A median (equatorial) layer of chambers is differentiated from the lateral chambers, seen most clearly in axial thin sections (Discocyclina).

  3. Superfamily Spirillinacea • The wall consists of a single crystal of calcite. They are small benthic forms often found adhering to algae and other hard substrates. • Spirillina has a long, planispiral second chamber and terminal aperture. • Patellina has a trochospiral to biserial test in which the chambers are subdivided by a scroll-like median septum and numerous transverse septulae.

  4. Spirillina Patellina

  5. Superfamily Duostominacea • The Duostominacea are an extinct group that may be intermediate in development between certain Endothracea and most Rotaliina. • This is suggested by the wall structure which consists of both optically radial and microgranular calcite. • In Duostomina (M. Triassic) the lowtrochospiral test has a basal aperture divided into two by a flap.

  6. Duostomina

  7. Superfamily Robertinacea • The Robertinacea have optically radial bilamellar walls composed of aragonite instead of calcite, although this may revert to the latter mineral with time in the fossil state. • The aperture is typically a basal slit extending up the face of the last chamber. • In Robertina the test is high trochospiral, each elongate chamber subdivided by transverse partitions. • Ceratobulimina(Upper Cretaceous) has a moderately low trochospiral test whilst that of Hoeglundina(M. Jurassic-Recent) is provided with a keel and peripheral slits marking the primary and relict (supplementary) apertures.

  8. Robertina Ceratobulimina Hoeglundina

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