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Achomosphaera alcicornu
From Fensome et al., 2019:
Achomosphaera alcicornu, (Eisenack, 1954b, p.65, pl.10, figs.1–2; text-fig.5) Davey and Williams, 1966a, p.50.
Holotype: Eisenack, 1954b, pl.10, fig.2.
Originally Hystrichosphaeridium, subsequently (and now) Achomosphaera.
Taxonomic junior synonyms: Galea lychnea and Hystrichosphaeridium leptodermum, both according to Sarjeant (1983, p.100–101).
May (1980, p.64) considered Hystrichosphaera (as Spiniferites) pseudofurcatus to be the possible taxonomic senior synonym of this species.
Age: Oligocene.
Locus typicus: Samland, East Prussia, Russia
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Original description as Hystrichosphaeridium alcicornu: [Eisenack, 1954, p. 65] (Translation: LPP):
Diagnosis:
Central body spherical to weakly oval, with numerous hollow processes, which are distally widened in a funnel-shaped fashion. These widenings divide into mostly 3, sometimes further subdivided tips, which are connected in an arch-like, so that there is a remote similarity with an elk's antlers.
Dimensions:
Holotype: sphere-diameter 65:67 µm, total diameter c. 157 µm; second specimen 58:65 µm and 152 µm respectively. 6 specimens with a sphere-diameter of 57-75 µm and a total diameter of c. 120-166 µm.
Affinities:
Most closely related is H. tubiferum (Ehrenberg) Deflandre. There is also a similarity with the processes of H. cf. furcata (Eisenack, 1954, p. 61). The processes are clearly transparent and homogeneous. Pylomes occur frequently.
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Improved description:
Davey and Williams, 1966:
Description:
The London Clay specimens are very similar to H. tertiara (Eisenack and Gocht) and differ only in the absence of clearly defined plate boundaries. A precingular archaeopyle is present. That the archaeopyle is precingular is determined by its shape and the presence of 5 surrounding processes. The apical process and the cingular processes are typically branched. As in all species of Achomosphaera only gonal processes are present. The occasional specimen in the London Clay is slightly granular and some possess processes that are perforate distally.
Dimensions:
Range: diameter of central body 49 - 66 µm, length of processes 24 - 46 µm.
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Supplemental description:
Hultberg, 1985, p. 106-107:
Description:
Chorate cyst, composed of endophragm and periphragm, closely appressed between processes. The surface of both endophragm and periphragm is smooth. The shape of the cyst is subspherical.
The ornamentation consists of gonal and intergonal processes. The process-bases are marked by a conical cavity, sometimes extending to the tip of the process. This cavity is absent in some processes. The process-tips are trifurcate at gonal positions, and bifurcate at intergonal positions. The furcation often has a ragged trumpet-shaped appearance. Also, the bifid nature of the furcae is often obscured by this structure. The apical processes, and the processes in the vicinity of the paracingulum are mostly of a complex nature. The processes at the paracingulum are often fused in pairs, and exhibit process-tips that are complexly branched.
Paratabulation can be incompletely discerned through the gonal and intergonal processes. The paratabulation is gonyaulacacean, paratabulation formula: 3-4', 6", xc, 5-6", 1''''. Possibly, paraplate 1''' is integrated in the parasulcus. Paraplate 1p is probably present, but is not discernible. Paraplate 6" appears to be distictly triangular.
The archeopyle is precingular, type P, formed by the detachment of paraplate 3". Operculum free.
Paracingulum is indicated by complexely branched processes.
Parasulcus is not indicated.
Dimension/Size:
80-94 µm (diameter).
Affinities:
Achomospharea alcicornu can be easily distinguished from other species of Achomosphaera by its characteristically branched processes, which resemble moose-horns.
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Gocht, 1969, p. 34, 35: (Translation: Geological Survey of Canada)
Additions/Remarks/Affinities:
This species was found in great numbers in many samples, and again, turns out to be an entire group of considerable variability. The differences which are most striking on the surface regard the shape of the processes. Since certain types of processes are also usually restricted to certain specimens, considerable contrasts in habit may arise. On many specimens, the affinity with Hystrichosphaera is clear, even independently of the type of archeopyle, from the areation. Very fine sutural lines connect the processes and demarcate fields. However, these lines are usually limited to the dorsal half of the body. Ventrally, they occur only in exceptional cases, and even then are incomplete. One specimen on which the areation is fully expressed shows clearly the boundaries of the longitudinal furrow and the cingulum. Elevated boundary lists are almost never formed, and some individuals are without any trace of areation. The distribution of the processes still requires further study. At least in the polar regions, there were considerable deviations. The processes, however different they may appear, can always be reduced to the same basic form. The hollow shaft widens into a shallow funnel with usually three horizontal branches, each of which divides once more at the end. The shafts are mostly unbranched; only at the poles, and more seldom at the level of the cingulum, they also are furcate into two or three branches. Specimens with long, narrow processes tend to have longer terminal spines, which frequently are recurved and separated by deep, rounded concavities. There may also be a further differentiation between branches, with formation of spines and further branching. An extreme example is the specimen in Plate 4 fig. 7, on which an open plexus of spines has developed at the distal end of the processes. This find is definitely linked with typical specimens by intermediate forms. (The processes, including spines, are hollow, and differ in this respect from those of Cordosphaeridium diktyoplokus (Klumpp), which are closest to them.) Other specimens have thickset processes with broad, planar branches which sometimes exhibit almost right-angled boundaries and only short projections at the corners. In exceptional cases, the process furcation may also exhibit circular or reticulate perforations. The obvious links with the genus Hystrichosphaera which constantly recur in Achomosphaera species are not surprising; they only emphasize the fluid and very difficult to define character of this entire form complex.
Occurrence: Paleocene- Middle Oligocene.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP
Achomosphaera alcicornu (Eisenack, 1954b) Davey and Williams, 1966. According to Gocht (1969, p.34), commonly has faint sutures. The processes can be complexly branched and even perforate but always show the same basic structure with the hollow stems branching into three: distal terminations bifurcate. Size: central body 49-66 µm, processes 29-46 µm.
Achomosphaera alcicornu, (Eisenack, 1954b, p.65, pl.10, figs.1–2; text-fig.5) Davey and Williams, 1966a, p.50.
Holotype: Eisenack, 1954b, pl.10, fig.2.
Originally Hystrichosphaeridium, subsequently (and now) Achomosphaera.
Taxonomic junior synonyms: Galea lychnea and Hystrichosphaeridium leptodermum, both according to Sarjeant (1983, p.100–101).
May (1980, p.64) considered Hystrichosphaera (as Spiniferites) pseudofurcatus to be the possible taxonomic senior synonym of this species.
Age: Oligocene.
Locus typicus: Samland, East Prussia, Russia
---------------------------------------------------------------------------------------------------
Original description as Hystrichosphaeridium alcicornu: [Eisenack, 1954, p. 65] (Translation: LPP):
Diagnosis:
Central body spherical to weakly oval, with numerous hollow processes, which are distally widened in a funnel-shaped fashion. These widenings divide into mostly 3, sometimes further subdivided tips, which are connected in an arch-like, so that there is a remote similarity with an elk's antlers.
Dimensions:
Holotype: sphere-diameter 65:67 µm, total diameter c. 157 µm; second specimen 58:65 µm and 152 µm respectively. 6 specimens with a sphere-diameter of 57-75 µm and a total diameter of c. 120-166 µm.
Affinities:
Most closely related is H. tubiferum (Ehrenberg) Deflandre. There is also a similarity with the processes of H. cf. furcata (Eisenack, 1954, p. 61). The processes are clearly transparent and homogeneous. Pylomes occur frequently.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Improved description:
Davey and Williams, 1966:
Description:
The London Clay specimens are very similar to H. tertiara (Eisenack and Gocht) and differ only in the absence of clearly defined plate boundaries. A precingular archaeopyle is present. That the archaeopyle is precingular is determined by its shape and the presence of 5 surrounding processes. The apical process and the cingular processes are typically branched. As in all species of Achomosphaera only gonal processes are present. The occasional specimen in the London Clay is slightly granular and some possess processes that are perforate distally.
Dimensions:
Range: diameter of central body 49 - 66 µm, length of processes 24 - 46 µm.
-------------------------------------------
Supplemental description:
Hultberg, 1985, p. 106-107:
Description:
Chorate cyst, composed of endophragm and periphragm, closely appressed between processes. The surface of both endophragm and periphragm is smooth. The shape of the cyst is subspherical.
The ornamentation consists of gonal and intergonal processes. The process-bases are marked by a conical cavity, sometimes extending to the tip of the process. This cavity is absent in some processes. The process-tips are trifurcate at gonal positions, and bifurcate at intergonal positions. The furcation often has a ragged trumpet-shaped appearance. Also, the bifid nature of the furcae is often obscured by this structure. The apical processes, and the processes in the vicinity of the paracingulum are mostly of a complex nature. The processes at the paracingulum are often fused in pairs, and exhibit process-tips that are complexly branched.
Paratabulation can be incompletely discerned through the gonal and intergonal processes. The paratabulation is gonyaulacacean, paratabulation formula: 3-4', 6", xc, 5-6", 1''''. Possibly, paraplate 1''' is integrated in the parasulcus. Paraplate 1p is probably present, but is not discernible. Paraplate 6" appears to be distictly triangular.
The archeopyle is precingular, type P, formed by the detachment of paraplate 3". Operculum free.
Paracingulum is indicated by complexely branched processes.
Parasulcus is not indicated.
Dimension/Size:
80-94 µm (diameter).
Affinities:
Achomospharea alcicornu can be easily distinguished from other species of Achomosphaera by its characteristically branched processes, which resemble moose-horns.
-------------------------------------------
Gocht, 1969, p. 34, 35: (Translation: Geological Survey of Canada)
Additions/Remarks/Affinities:
This species was found in great numbers in many samples, and again, turns out to be an entire group of considerable variability. The differences which are most striking on the surface regard the shape of the processes. Since certain types of processes are also usually restricted to certain specimens, considerable contrasts in habit may arise. On many specimens, the affinity with Hystrichosphaera is clear, even independently of the type of archeopyle, from the areation. Very fine sutural lines connect the processes and demarcate fields. However, these lines are usually limited to the dorsal half of the body. Ventrally, they occur only in exceptional cases, and even then are incomplete. One specimen on which the areation is fully expressed shows clearly the boundaries of the longitudinal furrow and the cingulum. Elevated boundary lists are almost never formed, and some individuals are without any trace of areation. The distribution of the processes still requires further study. At least in the polar regions, there were considerable deviations. The processes, however different they may appear, can always be reduced to the same basic form. The hollow shaft widens into a shallow funnel with usually three horizontal branches, each of which divides once more at the end. The shafts are mostly unbranched; only at the poles, and more seldom at the level of the cingulum, they also are furcate into two or three branches. Specimens with long, narrow processes tend to have longer terminal spines, which frequently are recurved and separated by deep, rounded concavities. There may also be a further differentiation between branches, with formation of spines and further branching. An extreme example is the specimen in Plate 4 fig. 7, on which an open plexus of spines has developed at the distal end of the processes. This find is definitely linked with typical specimens by intermediate forms. (The processes, including spines, are hollow, and differ in this respect from those of Cordosphaeridium diktyoplokus (Klumpp), which are closest to them.) Other specimens have thickset processes with broad, planar branches which sometimes exhibit almost right-angled boundaries and only short projections at the corners. In exceptional cases, the process furcation may also exhibit circular or reticulate perforations. The obvious links with the genus Hystrichosphaera which constantly recur in Achomosphaera species are not surprising; they only emphasize the fluid and very difficult to define character of this entire form complex.
Occurrence: Paleocene- Middle Oligocene.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP
Achomosphaera alcicornu (Eisenack, 1954b) Davey and Williams, 1966. According to Gocht (1969, p.34), commonly has faint sutures. The processes can be complexly branched and even perforate but always show the same basic structure with the hollow stems branching into three: distal terminations bifurcate. Size: central body 49-66 µm, processes 29-46 µm.