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Cleistosphaeridium lacustre
Cleistosphaeridium lacustre, Köhler and Clausing, 2000, p.42-43, pl.1, figs.1-6, figs.3a-d.
Holotype: Köhler and Clausing, 2000, pl.1, figs.1-2,4.
Locus typicus: Lake Enspel, Westerwald (Germany)
Stratum typicum: Upper Oligocene (MP 28)
Age: Late Oligocene.
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Original description: [Köhler and Clausing, 2000]:
Diagnosis:
A skolochorate cyst with a subspherical central body and numerous non-tabular processes. The fibrous processes are distally closed, and show acuminate, bifurcate and branched tips.
The autophragm between the processes is moderately ornamented.
An apical archaeopyle (Type tA) is present, characterized by a zigzag suture, which is sometimes difficult to observe ( Plate I, Fig. 3 and Fig. 4).
Dimensions:
The central body of the holotype measures 33.6 μm, and the processes are 7.1–8.6 μm long and 0.7–1.4 μm wide.
The morphological variation of this species was found to be as follows: the central body is between 26.4 and 37.1 μm in diameter.
The length of the processes is variable from 6.9 to 17.3 μm and the width from 0.5 to 3.6μm. The processes vary from a small to wide longitudinally shape. Fifty-three specimens were measured.
Affinities:
The dinoflagellates from Lake Enspel fit both the original description by Davey et al. (1966) and the modified description by Stover and Evitt (1978) for the genus Cleistosphaeridium. This is based on the holotype of Cleistosphaeridium diversispinosum Davey et al. (1966) from the Eocene London Clay. The central body of this species is slightly larger (38–43 μm), but the length of the processes is equivalent to Cleistosphaeridium lacustre (7–23 μm). The processes of Cleistosphaeridium diversispinosum display various shapes (branched, bifurcate, orthogonal), are variable in length, and are up to 5 μm in width in one specimen. In Cleistosphaeridium lacustre, the processes also vary in shape and length within one specimen, but their width never exceeds 3.1 μm. Currently, 40 valid species of Cleistosphaeridium have been described, 20 of which are reported from the Tertiary ( Lentin and Williams, 1993): four species from the Palaeocene, eight from the Eocene, two from the Oligocene, and six from the Palaeogene. Of these, only one, Cleistosphaeridium tenuum Harris (1973), was described from non-marine sediments, namely from the Palaeocene of the Darra Formation near Brisbane, Australia. These cysts are more or less circular in shape, with a length of 22–35 μm and a width of 18–25 μm. The processes are 4–5 μm long. The smaller size and especially the short processes distinguish this species from Cleistosphaeridium lacustre. Most of the Tertiary species (13) are described from Chinese publications, which are often inadequately described and figured and could only partially be used for comparison to Cleistosphaeridium lacustre. Thus, the size is often the only reliable differentiating characteristic, even if it differs slightly owing to preparation techniques used. The species described below are reported from marine sediments. This separates Cleistosphaeridium lacustre ecologically, but morphological differences are also obvious: Cleistosphaeridium baculatum He Chengquan and Li Peng (1981) from Upper Oligocene sediments of the Tarim Basin (China) has a larger central body (45–55 μm) and smaller processes (5–10 μm). Cleistosphaeridium digitale He Chengquan (1991) is almost twice the size (60–78 μm) with processes of 20–30 μm in length. This species is reported from Lower Eocene sediments of the Tarim Basin.Cleistosphaeridium elegans He Chengquan et al. (1989) is another species from the Palaeogene of the Tarim Basin. It has a central body that is 30–50 μm in diameter and 10–15 μm long hollow processes, making the species slightly larger than Cleistosphaeridium lacustre.Cleistosphaeridium panshanese Jiabo (1978) from the Palaeogene Dongpu Depression in China is a small species, the central body being 20–25 μm in maximum diameter. The hollow processes are comparably short, 3.5–7.5 μm in length.Cleistosphaeridium shandongense He Chengquan et al. (1989) from the same horizon is almost the same size as C. panshanese but differs in having processes that are 7–8 μm long.The central body of Cleistosphaeridium tianshanese He Chengquan (1991) from the Lower Eocene of the Tarim Basin is larger, but the process length (7–14 μm) is similar to that of Cleistosphaeridium lacustre.In conclusion, neither Tertiary nor Quaternary deposits have yielded any dinoflagellate species that are comparable to Cleistosphaeridium lacustre.
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Preservation:
The majority of dinoflagellate cysts are preserved in their entirety, with only the plates of the archaeopyle missing. This suggests sedimentation after germination. Most of the palynomorphs are preserved in an uncompressed state, embedded in tuff or diatomite horizons ( Fig. 4a and b). The resistance towards processing and the yellow–green fluorescence colour of the cyst walls suggest a possible composition of aliphatic biopolymers as has been observed by others in fossil dinoflagellate cysts.The autochthonous nature of the dinoflagellates is based on the following facts: (1) The mass accumulations of the cysts reach core depths of 140 m. (2) The dinoflagellate assemblage has a monospecific character. (3) The general excellent preservation with the delicate processes intact makes resedimentation of unknown palynomorphs from the Devonian basement impossible. (4) Input from the marine Oligocene seems to be unlikely because the sea was about 80 km away. According to the palaeogeographic reconstructions in use for the Oligocene, there was no connection to the sea (Hottenrott 1988). Hence, marine or saline water ingressions into the lake are excluded, because all associated diatoms are identified as freshwater species (Schiller, pers. commun.). (5) Based on the observation that the dinoflagellates are not present solely on cleavage planes but also occur in the underlying bedding, without structural disturbance (Clausing 1998), recent contamination is deemed impossible. Also, the fluorescence colour of the palynomorphs reflects alteration compared to recent material.
Holotype: Köhler and Clausing, 2000, pl.1, figs.1-2,4.
Locus typicus: Lake Enspel, Westerwald (Germany)
Stratum typicum: Upper Oligocene (MP 28)
Age: Late Oligocene.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Köhler and Clausing, 2000]:
Diagnosis:
A skolochorate cyst with a subspherical central body and numerous non-tabular processes. The fibrous processes are distally closed, and show acuminate, bifurcate and branched tips.
The autophragm between the processes is moderately ornamented.
An apical archaeopyle (Type tA) is present, characterized by a zigzag suture, which is sometimes difficult to observe ( Plate I, Fig. 3 and Fig. 4).
Dimensions:
The central body of the holotype measures 33.6 μm, and the processes are 7.1–8.6 μm long and 0.7–1.4 μm wide.
The morphological variation of this species was found to be as follows: the central body is between 26.4 and 37.1 μm in diameter.
The length of the processes is variable from 6.9 to 17.3 μm and the width from 0.5 to 3.6μm. The processes vary from a small to wide longitudinally shape. Fifty-three specimens were measured.
Affinities:
The dinoflagellates from Lake Enspel fit both the original description by Davey et al. (1966) and the modified description by Stover and Evitt (1978) for the genus Cleistosphaeridium. This is based on the holotype of Cleistosphaeridium diversispinosum Davey et al. (1966) from the Eocene London Clay. The central body of this species is slightly larger (38–43 μm), but the length of the processes is equivalent to Cleistosphaeridium lacustre (7–23 μm). The processes of Cleistosphaeridium diversispinosum display various shapes (branched, bifurcate, orthogonal), are variable in length, and are up to 5 μm in width in one specimen. In Cleistosphaeridium lacustre, the processes also vary in shape and length within one specimen, but their width never exceeds 3.1 μm. Currently, 40 valid species of Cleistosphaeridium have been described, 20 of which are reported from the Tertiary ( Lentin and Williams, 1993): four species from the Palaeocene, eight from the Eocene, two from the Oligocene, and six from the Palaeogene. Of these, only one, Cleistosphaeridium tenuum Harris (1973), was described from non-marine sediments, namely from the Palaeocene of the Darra Formation near Brisbane, Australia. These cysts are more or less circular in shape, with a length of 22–35 μm and a width of 18–25 μm. The processes are 4–5 μm long. The smaller size and especially the short processes distinguish this species from Cleistosphaeridium lacustre. Most of the Tertiary species (13) are described from Chinese publications, which are often inadequately described and figured and could only partially be used for comparison to Cleistosphaeridium lacustre. Thus, the size is often the only reliable differentiating characteristic, even if it differs slightly owing to preparation techniques used. The species described below are reported from marine sediments. This separates Cleistosphaeridium lacustre ecologically, but morphological differences are also obvious: Cleistosphaeridium baculatum He Chengquan and Li Peng (1981) from Upper Oligocene sediments of the Tarim Basin (China) has a larger central body (45–55 μm) and smaller processes (5–10 μm). Cleistosphaeridium digitale He Chengquan (1991) is almost twice the size (60–78 μm) with processes of 20–30 μm in length. This species is reported from Lower Eocene sediments of the Tarim Basin.Cleistosphaeridium elegans He Chengquan et al. (1989) is another species from the Palaeogene of the Tarim Basin. It has a central body that is 30–50 μm in diameter and 10–15 μm long hollow processes, making the species slightly larger than Cleistosphaeridium lacustre.Cleistosphaeridium panshanese Jiabo (1978) from the Palaeogene Dongpu Depression in China is a small species, the central body being 20–25 μm in maximum diameter. The hollow processes are comparably short, 3.5–7.5 μm in length.Cleistosphaeridium shandongense He Chengquan et al. (1989) from the same horizon is almost the same size as C. panshanese but differs in having processes that are 7–8 μm long.The central body of Cleistosphaeridium tianshanese He Chengquan (1991) from the Lower Eocene of the Tarim Basin is larger, but the process length (7–14 μm) is similar to that of Cleistosphaeridium lacustre.In conclusion, neither Tertiary nor Quaternary deposits have yielded any dinoflagellate species that are comparable to Cleistosphaeridium lacustre.
-------------------------------------------------------------------------------------------------------
Preservation:
The majority of dinoflagellate cysts are preserved in their entirety, with only the plates of the archaeopyle missing. This suggests sedimentation after germination. Most of the palynomorphs are preserved in an uncompressed state, embedded in tuff or diatomite horizons ( Fig. 4a and b). The resistance towards processing and the yellow–green fluorescence colour of the cyst walls suggest a possible composition of aliphatic biopolymers as has been observed by others in fossil dinoflagellate cysts.The autochthonous nature of the dinoflagellates is based on the following facts: (1) The mass accumulations of the cysts reach core depths of 140 m. (2) The dinoflagellate assemblage has a monospecific character. (3) The general excellent preservation with the delicate processes intact makes resedimentation of unknown palynomorphs from the Devonian basement impossible. (4) Input from the marine Oligocene seems to be unlikely because the sea was about 80 km away. According to the palaeogeographic reconstructions in use for the Oligocene, there was no connection to the sea (Hottenrott 1988). Hence, marine or saline water ingressions into the lake are excluded, because all associated diatoms are identified as freshwater species (Schiller, pers. commun.). (5) Based on the observation that the dinoflagellates are not present solely on cleavage planes but also occur in the underlying bedding, without structural disturbance (Clausing 1998), recent contamination is deemed impossible. Also, the fluorescence colour of the palynomorphs reflects alteration compared to recent material.