Superfamilies: Orbitodacea, Spirillinacea, Duostominacea and Robertinacea

About This Presentation

Title:

Superfamilies: Orbitodacea, Spirillinacea, Duostominacea and Robertinacea

Description:

The orbitoids are a Late Cretaceous to Miocene group of 'larger foraminifera' ... Patellina has a trochospiral to biserial test in which the chambers are ... – PowerPoint PPT presentation

Number of Views:66

Avg rating:3.0/5.0

Slides: 14

Provided by: nam5101

Category:

more less

Transcript and Presenter's Notes

Title: Superfamilies: Orbitodacea, Spirillinacea, Duostominacea and Robertinacea

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
(No Transcript)
4
(No Transcript)
5
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.

6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
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 low trochospiral
test has a basal aperture divided into two by a
flap.

11
(No Transcript)
12
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.