2 Systematic Descriptions
27
Description: Small, about 20 µ in diameter. Spherical test with a smooth inner
wall 1–1.5 µ thick. Outer membrane thin and structured—reticulate. Reticulum
consists of muri 1.5 µ in thickness surrounded by brochi of up to 4 µ across. A
small rounded germination aperture is apparent in some specimen.
Dimensions: 15–30 µ (mean 21 µ) (30 specimens measured). Known distribution:
Lower Permian of India (Tiwari 1964).
Discussion: The minute size and smooth membrane of this acritarch are its distinguishing feature. The membrane enveloping the spore in C. gondwanensis is
intra-punctate to intra-granulate which is the structure that distinguishes it from
C. microreticulata.
Sub-group Acanthomorphitae (Downie, Evitt and Sarjeant 1963).
Genus Mehlisphaeridium (Segroves 1967).
Test spheroidal. Two-layered wall; sculptured as well as structured. Sculpture
consists of hollow and differentially thickened processes. Structure infra-punctate.
Known distribution: Artinskian to Upper Permian of the Perth Basin (Segroves
1967), Permian of Collie Basin (Backhouse 1991).
Mehlisphaeridium fibratum (Segroves 1967) (Fig. 2.10).
Occurrence: Lower Permian (Artinskian?) to Upper Permian of Collie Basin, Site
B bore 1641
, 224-27
.
Description: Spheroidal test. Two-layered wall. Inner wall solid, rather thick, up
to 2 µ, overlain by an outer transparent membrane. Membrane sculptured and
structured. Structure is infra-punctate. Sculpture consists of numerous pseudoechinate processes, varying in length from 4 to 20 µ and tapering at their ends.
Membranous processes are reinforced by columnar thickenings of the membrane
(see reconstructed specimen).
Faint indication of vein structure can be sometimes observed in the linear arrangement of the structural elements along the thickenings. The thickenings vary in
number in one process from three to five. The total number of processes varies
from 10 to more than 20 in different specimen.
Dimensions: 30–50 µ in diameter (20 specimens measured) (Fig. 2.10).
Genus Tetraporina (Naumova 1953, 1961).
Diagnosis: Test quadrilateral. Apices rounded. Wall one-layered, smooth to
granulate. Arcuate folds may or may not be present around apices.
Known distribution: Lower Carboniferous of Moscow Basin (Naumova 1953,
1961), Lower Carboniferous of Spitzbergen (Playford 1965), Carboniferous of
Canada (Staplin 1960), Lower Permian of Victoria (Pant and Mehra 1963),
Lower Triassic of Western Australia (Balme 1963), Carboniferous of Saudi Arabia
(Hemer and Nygreen 1967).
Discussion: Playford (1965) discussed the affinity of Tetraporina and suggested
an algal origin. Scott, Barghoorn and Leopold (1960) also noted its resemblance
to the unicellular green alga Tetraedron. Churchill (1960) recovered forms closely
resembling Tetraporina from recent and tertiary deposits in Western Australia.
27
Description: Small, about 20 µ in diameter. Spherical test with a smooth inner
wall 1–1.5 µ thick. Outer membrane thin and structured—reticulate. Reticulum
consists of muri 1.5 µ in thickness surrounded by brochi of up to 4 µ across. A
small rounded germination aperture is apparent in some specimen.
Dimensions: 15–30 µ (mean 21 µ) (30 specimens measured). Known distribution:
Lower Permian of India (Tiwari 1964).
Discussion: The minute size and smooth membrane of this acritarch are its distinguishing feature. The membrane enveloping the spore in C. gondwanensis is
intra-punctate to intra-granulate which is the structure that distinguishes it from
C. microreticulata.
Sub-group Acanthomorphitae (Downie, Evitt and Sarjeant 1963).
Genus Mehlisphaeridium (Segroves 1967).
Test spheroidal. Two-layered wall; sculptured as well as structured. Sculpture
consists of hollow and differentially thickened processes. Structure infra-punctate.
Known distribution: Artinskian to Upper Permian of the Perth Basin (Segroves
1967), Permian of Collie Basin (Backhouse 1991).
Mehlisphaeridium fibratum (Segroves 1967) (Fig. 2.10).
Occurrence: Lower Permian (Artinskian?) to Upper Permian of Collie Basin, Site
B bore 1641
, 224-27
.
Description: Spheroidal test. Two-layered wall. Inner wall solid, rather thick, up
to 2 µ, overlain by an outer transparent membrane. Membrane sculptured and
structured. Structure is infra-punctate. Sculpture consists of numerous pseudoechinate processes, varying in length from 4 to 20 µ and tapering at their ends.
Membranous processes are reinforced by columnar thickenings of the membrane
(see reconstructed specimen).
Faint indication of vein structure can be sometimes observed in the linear arrangement of the structural elements along the thickenings. The thickenings vary in
number in one process from three to five. The total number of processes varies
from 10 to more than 20 in different specimen.
Dimensions: 30–50 µ in diameter (20 specimens measured) (Fig. 2.10).
Genus Tetraporina (Naumova 1953, 1961).
Diagnosis: Test quadrilateral. Apices rounded. Wall one-layered, smooth to
granulate. Arcuate folds may or may not be present around apices.
Known distribution: Lower Carboniferous of Moscow Basin (Naumova 1953,
1961), Lower Carboniferous of Spitzbergen (Playford 1965), Carboniferous of
Canada (Staplin 1960), Lower Permian of Victoria (Pant and Mehra 1963),
Lower Triassic of Western Australia (Balme 1963), Carboniferous of Saudi Arabia
(Hemer and Nygreen 1967).
Discussion: Playford (1965) discussed the affinity of Tetraporina and suggested
an algal origin. Scott, Barghoorn and Leopold (1960) also noted its resemblance
to the unicellular green alga Tetraedron. Churchill (1960) recovered forms closely
resembling Tetraporina from recent and tertiary deposits in Western Australia.