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Melitasphaeridium choanophorum var. choanophorum
Melitasphaeridium choanophorum var. choanophorum
Autonym
Holotype: Deflandre and Cookson, 1955, text-fig.23-26
Paratypes: Deflandre and Cookson, 1955
Locus typicus: Hampton (near Melbourne), Victoria, Australia
Stratum typicum: Pliocene
Original description: Deflandre and Cookson 1955, p. 271: Hystrichosphaeridium choanophorum
Shell globular, furnished with tubular processes not communicating with the interior. Processes cylindro-conical, abruptly widened into a small funnel with a rough margin, sometimes into a flat expansion with a finely denticulate margin, or rarely, terminated by 2 recurved spine-like outgrowths. Membrane smooth or indistinctly granular.
Dimensions: Shell: 30-34 Ám; Processes: 15-17 Ám long; Overall diameter: 54-63 Ám.
Emended diagnosis: Harland and Hill, 1979, p. 39, 41: Melitasphaeridium choanophorum
Spherical to subspherical chorate cysts possessing hollow, tubular processes that have flared, stellate distal tips of variable morphology. The processes reflect a paratabulation of pr, 4", 6"", 0-6c, 6""", 1p, 1"""", from their formula: pr, 4", 6"", 0-6c, 5""", 1p, 1"""". Archeopyle precingular, ?enlarged, by loss of paraplate 3"". Description: A chorate cyst made up of two wall layers that are continuous and conspicous. Wall layers are smooth to microreticulate. Processes are made up entirely of periphragm, are hollow and tubular and do not connect to the interior of the cyst. The processes are approximately half the diameter of the central body in length and are rigid to sligthly flexuous. The distal ends of the process which open to the anterior are flared and basically star-shaped but are extremely variable in morphology. In some the tips are infundibular with an array of short spines along the margin, whereas in others the star-shape is much more pronounced with a fewer number of long spines and in one extreme the spines are extremely long and almost link the one process to another like trabeculae. A study of the disposition of the disposition of the intratabular processes on the cyst body has led us to postulate a paratabulation of pr, 4", 6"", 0-6c, 6""", 1p, 1"""". In particular seventeen processes are recognised, a prominent apical process reflecting an apical pore closing plate, no cingular processes, five post-cingular processes, the 1""" paraplate not being representated by a process, with a ?posterior intercalary process and a single antapical process giving a process formula of pr, 4", 6"", 0-6c, 5""", 1p, 1"""". It is possible from the relative position of the ?posterior intercalary process and the antapical process that the former may be a posterior sulcal process. It may be argued also that the 1" as designated herein is an as process and that the pr process is, in fact, a 1" process. Six paracingular processes may or may not be present. The archeopyle is formed by the loss of a single precingular paraplate (3"") and because of its relative size in relation to the cyst it may be enlarged.
Affinities:
Deflandre and Cookson 1955, p. 271-272
Hystrichosphaeridium choanophorum. The type of process having funnel-shaped terminations with almost smooth margins is at present known only in 1 species, namely, in Hystrichosphaeridium simplex (White) Defl., found by White in English Senonian flints. H.simplex, which as yet has not been rediscovered, is considerably larger (c. 100Á overall) than H.choanophorum. Our two specimens possess both funnel-like processes and others that recall the process of Hystrichosphaeridium tubiferum sensu lato of the European Cretaceous flints. It must be remembered, however, that in H.tubiferum the bases of the processes are open so that the inner cavity of the shell is in direct communication, through the processes, with the exterior, whereas in H. choanophorum the bases are closed.
Harland and Hill, 1979, p. 41
To the authors" knowledge no cysts of similar morphology are recorded from Miocene sediments. Care must be taken, however, in not confusing it with the cysts of Homotryblium Davey and Williams which differ in possessing an epicystal archeopyle, and in certain Impletosphaeridium Morgenroth cysts which may be of similar size and have similar process tips. The latter differ, however, in having solid processes.
Autonym
Holotype: Deflandre and Cookson, 1955, text-fig.23-26
Paratypes: Deflandre and Cookson, 1955
Locus typicus: Hampton (near Melbourne), Victoria, Australia
Stratum typicum: Pliocene
Original description: Deflandre and Cookson 1955, p. 271: Hystrichosphaeridium choanophorum
Shell globular, furnished with tubular processes not communicating with the interior. Processes cylindro-conical, abruptly widened into a small funnel with a rough margin, sometimes into a flat expansion with a finely denticulate margin, or rarely, terminated by 2 recurved spine-like outgrowths. Membrane smooth or indistinctly granular.
Dimensions: Shell: 30-34 Ám; Processes: 15-17 Ám long; Overall diameter: 54-63 Ám.
Emended diagnosis: Harland and Hill, 1979, p. 39, 41: Melitasphaeridium choanophorum
Spherical to subspherical chorate cysts possessing hollow, tubular processes that have flared, stellate distal tips of variable morphology. The processes reflect a paratabulation of pr, 4", 6"", 0-6c, 6""", 1p, 1"""", from their formula: pr, 4", 6"", 0-6c, 5""", 1p, 1"""". Archeopyle precingular, ?enlarged, by loss of paraplate 3"". Description: A chorate cyst made up of two wall layers that are continuous and conspicous. Wall layers are smooth to microreticulate. Processes are made up entirely of periphragm, are hollow and tubular and do not connect to the interior of the cyst. The processes are approximately half the diameter of the central body in length and are rigid to sligthly flexuous. The distal ends of the process which open to the anterior are flared and basically star-shaped but are extremely variable in morphology. In some the tips are infundibular with an array of short spines along the margin, whereas in others the star-shape is much more pronounced with a fewer number of long spines and in one extreme the spines are extremely long and almost link the one process to another like trabeculae. A study of the disposition of the disposition of the intratabular processes on the cyst body has led us to postulate a paratabulation of pr, 4", 6"", 0-6c, 6""", 1p, 1"""". In particular seventeen processes are recognised, a prominent apical process reflecting an apical pore closing plate, no cingular processes, five post-cingular processes, the 1""" paraplate not being representated by a process, with a ?posterior intercalary process and a single antapical process giving a process formula of pr, 4", 6"", 0-6c, 5""", 1p, 1"""". It is possible from the relative position of the ?posterior intercalary process and the antapical process that the former may be a posterior sulcal process. It may be argued also that the 1" as designated herein is an as process and that the pr process is, in fact, a 1" process. Six paracingular processes may or may not be present. The archeopyle is formed by the loss of a single precingular paraplate (3"") and because of its relative size in relation to the cyst it may be enlarged.
Affinities:
Deflandre and Cookson 1955, p. 271-272
Hystrichosphaeridium choanophorum. The type of process having funnel-shaped terminations with almost smooth margins is at present known only in 1 species, namely, in Hystrichosphaeridium simplex (White) Defl., found by White in English Senonian flints. H.simplex, which as yet has not been rediscovered, is considerably larger (c. 100Á overall) than H.choanophorum. Our two specimens possess both funnel-like processes and others that recall the process of Hystrichosphaeridium tubiferum sensu lato of the European Cretaceous flints. It must be remembered, however, that in H.tubiferum the bases of the processes are open so that the inner cavity of the shell is in direct communication, through the processes, with the exterior, whereas in H. choanophorum the bases are closed.
Harland and Hill, 1979, p. 41
To the authors" knowledge no cysts of similar morphology are recorded from Miocene sediments. Care must be taken, however, in not confusing it with the cysts of Homotryblium Davey and Williams which differ in possessing an epicystal archeopyle, and in certain Impletosphaeridium Morgenroth cysts which may be of similar size and have similar process tips. The latter differ, however, in having solid processes.