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Cordosphaeridium inodes
Cordosphaeridium inodes (Klumpp, 1953) Eisenack, 1963; emend. Morgenroth, 1968; emend. Sarjeant, 1981
Originally Hystrichosphaeridium, subsequently (and now) Cordosphaeridium. Jain and Garg (1986b, p.64-65) considered Cordosphaeridium sangchamallae to be a possible taxonomic junior synonym of this species. Age: Late Eocene.
Possible tax. sr. synonym of Cordosphaeridium sangchamallai Mehrotra and Sinha, 1981, according to Jain and Garg, 1986.
Holotype: Klumpp, 1953, pl.18, fig.1-2; Sarjeant, 1981, pl.1, fig.1, text-fig.1
Paratypes: Klumpp, 1953
Locus typicus: W÷hrden near Heide, Holstein, Germany
Stratum typicum: Late Eocene
Translation Klumpp, 1953: Sarjeant, 1981, p. 103
Translations Eisenack, 1963 and Morgenroth, 1968: LPP
Translation Gocht, 1969: Geological Survey of Canada
Original description: Klumpp, 1953, p. 391-392: Hystrichosphaeridium inodes
A species of the genus Hystrichosphaeridium with the following differentiating characteristics: the membrane of the shell is two-layered, the outer layer consisting of short fibres, perpendicular to the surface. From this layer of fibres are formed the processes, which at their tips irregularly separate into threads.
Emended diagnosis: Morgenroth, 1968, p. 550
(supplementary to the diagnosis of the genus) Theca generally clearly ellipsoidal, sometimes with small apical and antapical bulges. The massive processes are built from the fibrous layer of the thecal wall, tapering distally in a trumpet-shaped fashion. The length of the processes varies considerably per specimen (differences in lenght of up to 15 Ám have been observed). A number of specimens shows the tendency of a distal interconnection of neighbouring processes. The arrangement of processes is as follows: 4 apical processes - sometimes coalescing - characterize the apex. A further apical process is located on the epitheca in direct line with the ventral longitudinal zone. Above the girdle zone, 6 precingular processes are present. In some specimens, the laevorotatory girdle is characterized by an continuous fibrous band. In most of the specimens, 6 processes, more or les streched in the direction of the girdle, can be observed in that place. The girdle is interrupted ventrally by a narrow longitudinal zone, on the hypothecal part of which a small process is sometimes present. On the hypotheca, 6 postequatorial and 1 long antapical process can be discerned. In a few specimens, however, a further small process is located below 1""", taking the position of an intercalary plate. (Presumably, the intercalary process sometimes fuses with 1""" into a more robust process.)
Dimensions: theca length 68 (53/81) Ám, theca width 59 (50/70) Ám, process length c. 25-30 (19/43) Ám. 150 measurements, 1200 specimens studied.
Emended diagnosis Sarjeant, 1981, p. 103
Cyst spheroidal to broadly ovoidal, two-layered. The periphragm surface may be granulate to shagreenate or may bear striae or rugulae, variably developed. Some 21 processes arise from the periphragm of the complete cyst, each having rootlike proximal extensions of variable length; paratabulation 4", 6"", 0c, 5"""", 0p, 1"""", 0s. The length of the processes is in general around 35-40 % of the shortest cyst diameter; the antapical process, however, is longer and may exceed 50 % of that diameter. They are always fibrous and stout, though with some positional variation in size, but otherwise show considerable variation in form: several are bifurcate, sometimes forking towards their distal end, in other instances dividing so close to their proximal end as to effectively comprise two processes with linked bases. Distally they may be bifid or trifid to multifurcate, with branches of equal to markedly unequal length; the processes themselves, their forks or their branches may be capitate, oblate or foliate. Archaeopyle single-plate precingular (type P), formed by loss of the third precingular paraplate: operculum free.
Dimensions. Length of cyst 64 Ám, breath c. 62 Ám, length of processes 28-36 Ám.
Description. The periphragm wall bears a very variable ornament; sometimes it is faintly granular or punctate, more commonly it is shagreenate, with or without striae or rugulae which may be irregularly distributed, may relate in position in part to process bases (as secondary ,,rootlets" extending out from the rootlike exensions of those bases) or may form an irregular overall areolation extending over a part of, or the whole, surface. The very regular areolate pattern depicted in Klummp"s original drawing (1953, pl.18 fig. 2) appears, however, to be simply an artistic artefact; neither the holotype nor any other specimen examined shows such a pattern.
The processes vary greatly in form. They may bifurcate at about half or at about two thirds length, e.g. processes 4"",5"", 4""" and 5""" of the holotype (Text-fig.1), or so close to their bases that the process linkage is not readily observed, e.g.1", corresponding to the elongate first apical paraplate, in the holotype. In other processes, schism occurs only at the tips and may simulate the spreading fingers of an open hand. All processes are conspicuously fibrous; the number of fibres is consistently much greater than the number of distal branches. In no instance was any distal linkage observed between adjacent processes. The bifid postcingular processes may represent a fusion of these processes with the cingulars; indeed, they are not in the normal situation where postcingulars would be expected, but instead show a displacement toward the anterior.
The antapical process is consistently longest; it is normally or constantly tubiform to slightly tapering. The apical processes are shorter than those of the postcingular series. Cingular and sulcal processes were absent from all specimens examined.
Type Material.16 specimens. Range of Dimensions: Length of cyst 52-76 Ám, length of processes 20-40 Ám.
Davey and Williams, 1966, p. 84
C. inodes has a fibrous body wall, bearing processes which give the reflected tabulation typical of this genus. The variability of processes, noticed by Klumpp, has also been observed in the London Clay forms, especially in the sulcal region. The processes are either hollow, open distally with an ellipsoidal cross-section or taeniate. The process walls of the London Clay specimens are extremely fibrous and appear to be thinner than in the type material, perhaps due to oxidation within the sediment.
Gocht, 1969, p.36-41:
This species has been studied by a number of authors- most recently, by Morgenroth, 1968 and by Davey and Williams. Their respective definitions are very different from one another, but it is commonly agreed that the distribution of processes on the main body of C. inodes is not random, but governed by some rules. My investigations on the Meckelfeld material corroborate this view.
Davey and Williams assume that the archeopyle of Cordosphaeridium is located apically, so that the process on the operculum corresponds to the (only) apical process, and it is followed below by the precingular series with six processes, the cingular series with six, and the postcingular series with six. The antapex would then have one plate; an intercalary process 1p could be present.
In contrast, Morgenroth interprets the archeopyle as a precingular plate, citing as evidence the observation of cingulumlike fimbriae below the archeopyle margin. He counts five apical processes, six precingulars and six postcingulars, six cingular processes, and one antapical process, sometimes with a few additional accessory processes. As will be shown, the Meckelfeld material- ca. 29,000 specimens of C. inodes were prepared- does not fit either of these schemata. Moreover, it gives us an idea of the variability of this species, which affects especially the shape, length, number and arrangement of the processes.
The following general statements apply:
1. Subspecies of C. inodes which occur in Meckelfeld (C. inodes inodes, C. inodes gracilis, and C. inodes robustum) are linked by intermediate forms. Nevertheless, they shall still be treated as subspecies.
2. No equivalent of a cingulum or other aids to orientation were found, but the shape of the archeopyle definitely indicates a precingular location.
3. The number of processes is variable. However, this is not inconsistent with a regular arrangement. The variation affects only particular groups of processes, while others are constant.
On specimens which have not been crushed, the archeopyle is approximately horseshoe- shaped, frequently with rounded corners. Not infrequently, however, a 6-angled type of opening is seen. The broader base, positioned with the cingulum downward, is gently sinuate with a medial apex. The angles on the apical side are usually less distinct. The angulate type of pylome definitely indicates a connection with the original tabulation. This impression is strengthened when we observe notches or- on deformed specimens- inward cracks. The shape of the pylome and notches suggest that this archeopyle is homologous with that of Hystrichosphaera, with the basal notch perhaps representing the medial ridge of the rhomboid cingulum. As stated previously, the number and distribution of processes are regular, but show extensive variation. We must differentiate in this connection between elements which always have the same number and location, and others which are not constant. To describe this situation, the processes may be provisionally designated with letters, differentiating between paired and azygous processes. The plane of symmetry is the sagittal plane. The following processes are constant: the paired elements A, B, and C around the archeopyle, pair D on the hypotheca and the azygous Ap processes (at the apex), P (on the operculum)f and H and E (located toward the ventral side). Lateral processes F and G are usually paired, but sometimes only on one side, or asymmetrical. Opposite the archeopyle there is a series of processes of very variable number. Often there are only four (including E and H), sometimes with a scar or a small spine in the middle. The number six is also frequent, again occasionally with one or more elements in the center. In many samples, forms with thin processes in the ventral region were predominant. Occasionally an additional thin process ("a") occurs also on the dorsal side, directly under the medial notch of the archeopyle margin. The lowest number observed was 19; but there can also be 25 or more. Probably the number usually falls between 20 and 25. Figure 27 shows the constancy of the dorsal processes and the variability of the ventral processes.
It is not easy to reconcile these results with the findings of other authors. The first attempt to link regular arrangements of processes on "hystrichospheres" with dinoflagellate tabulation was made by Evitt, 1963, who at the same time interpreted the processes as elements of the cyst body which were connected with the plates of the surrounding theca (which is not preserved). Davey, Downie, Sarjeant and Williams followed this view. Also Morgenroth, 1968?, as previously mentioned, identified the processes of Cordosphaeridium and other genera with dinoflagellate plates. If we assume the above hypothesis that the archeopyle of Cordosphaeridium is homologous with that of Hystrichosphaera (i.e., the 3"" plate), and if we further consider the fact that the archeopyle process is always located centrally, then it becomes difficult to imagine how the processes could have a regular arrangement without being connected with the arrangement of thecal plates. On the other hand, if we regard the dorsal half of the body, we see that the Gonyaulax-Hystrichosphaera schema (6""-6c-6""") does not apply to the specimens examined here if we take the number of processes to equal the number of plates. Process pairs C and D do not alternate, as we should expect from the rhomboid cingular fields and the postcingulars. Altogether, the number of hypothecal processes is far too small, which is also why Davey and Williams, 1966 moved the archeopyle to the apex. I could not find an ideal solution; however, certain observations point to a possible explanation which seems to be worth pursuing.
The occasional occurrence of a process "a" below the middle of the pylome, at the very spot where it is most certain that a plate was not centered, suggests further comparisons with Hystrichosphaera. For, this observation itself already establishes that there can be sutural ("intertabular") as well as central ("intratabular" Evitt) processes: Two superposed systems of processes can be constructed, one intratabular (as assumed for Hystrichosphaeridium) and the other intertabular (as in Hystrichosphaera). As a rule; one of these two systems remains latent or is completely recessive. If we move the three hypothecal processes D1 + D2 + E in Cordosphaeridium to the intersections formed by a pentangular apical field with the boundaries of the postcingulars, we can quite easily construct a tabulation of the Hystrichosphaera type. The tabulation formula would then be 3", 6"", 6c, 5""", 1"""".
However, the situation in the ventral region remains uncertain; also here, where concentrations of small processes occasionally occur, these processes need not always each correspond to one plate, but may have occurred simultaneously on plate boundaries and in the center. On the other hand, even the longitudinal furrow of Hystrichosphaera is frequently strongly differentiated and divided into more or less open fields. Also, we have to allow for the presence of intercalary ventral plates. Sometimes double processes occur, with the two bases close together. These may result from one process coming apart into its main strands. The main shafts then remain connected only by thin threads which eventually also break. Such cases happen only in C. inodes inodes. As already mentioned, P. Morgenroth, 1968?, who carefully examined 1200 specimens of C. inodes, arrived at different results. Although he too points out the extensive variation, he reports five apical processes and six precingulars as constant. It remains for further research to resolve this discrepancy and perhaps differentiate primitive and derived forms. Of course, among thousands of specimens, deviations and special formations which can not be explained were repeatedly observed. Not all of these can be mentioned. I shall discuss only one: Some specimens have openings which are circular and have a greater diameter than the normal archeopyle. Unfortunately, no single explanation can be given for all such openings, since it was discovered that circular tearing can be caused also by injuries; in such cases, usually there is also a true archeopyle on the same individual. However, the openings in the objects in pl.1, fig.13 and 14, which exhibit narrow fringes, seem to have a biological origin.
C. inodes is the most frequent plankton species in the Early Eocene of Meckelfeld. In many samples, the spectrum of forms is marked decisively by C. inodes, and frequently one can even speak of "inodes assemblages" which also characterize other cores and open exposures in the NW German Eocene. Given the range of variation of C. inodes, its division into subspecies has only limited value;
in some samples, the division is very well attested, while in others it is difficult to separate the forms. In particular, an unbroken chain of transitional forms is observed between C. inodes inodes and C. inodes gracilis.
Cordosphaeridium cf. inodes (Klumpp)
A few specimens from different samples of the upper Late Eocene resemble C. inodes but are striking for the reticulate surface (external membrane) sculpture of the main body and the coarser-fibered process structure. The ends of the processes can be slender and fanlike or deeply slit and coming apart. The process arrangement, at least dorsally, corresponds with that of C. inodes. Ventrally, sometimes there are many thin processes, which may be connected by low basal lists. The reticulate sculpture is not quite as coarse-meshed as that of C. funiculatum Morgenroth. However, also specimens of C. inodes can have coarse-meshed reticulate sculpture, as is shown by a specimen of Eisenack which, judging from its type of processes, would belong, as the author states, to C. inodes gracilis (Eisenack, 1954)
Measurements: Maximal extension 121-157 Ám, main body diameter 61-78 Ám.
Occurrence: Early Eocene- ?Late Eocene.
Originally Hystrichosphaeridium, subsequently (and now) Cordosphaeridium. Jain and Garg (1986b, p.64-65) considered Cordosphaeridium sangchamallae to be a possible taxonomic junior synonym of this species. Age: Late Eocene.
Possible tax. sr. synonym of Cordosphaeridium sangchamallai Mehrotra and Sinha, 1981, according to Jain and Garg, 1986.
Holotype: Klumpp, 1953, pl.18, fig.1-2; Sarjeant, 1981, pl.1, fig.1, text-fig.1
Paratypes: Klumpp, 1953
Locus typicus: W÷hrden near Heide, Holstein, Germany
Stratum typicum: Late Eocene
Translation Klumpp, 1953: Sarjeant, 1981, p. 103
Translations Eisenack, 1963 and Morgenroth, 1968: LPP
Translation Gocht, 1969: Geological Survey of Canada
Original description: Klumpp, 1953, p. 391-392: Hystrichosphaeridium inodes
A species of the genus Hystrichosphaeridium with the following differentiating characteristics: the membrane of the shell is two-layered, the outer layer consisting of short fibres, perpendicular to the surface. From this layer of fibres are formed the processes, which at their tips irregularly separate into threads.
Emended diagnosis: Morgenroth, 1968, p. 550
(supplementary to the diagnosis of the genus) Theca generally clearly ellipsoidal, sometimes with small apical and antapical bulges. The massive processes are built from the fibrous layer of the thecal wall, tapering distally in a trumpet-shaped fashion. The length of the processes varies considerably per specimen (differences in lenght of up to 15 Ám have been observed). A number of specimens shows the tendency of a distal interconnection of neighbouring processes. The arrangement of processes is as follows: 4 apical processes - sometimes coalescing - characterize the apex. A further apical process is located on the epitheca in direct line with the ventral longitudinal zone. Above the girdle zone, 6 precingular processes are present. In some specimens, the laevorotatory girdle is characterized by an continuous fibrous band. In most of the specimens, 6 processes, more or les streched in the direction of the girdle, can be observed in that place. The girdle is interrupted ventrally by a narrow longitudinal zone, on the hypothecal part of which a small process is sometimes present. On the hypotheca, 6 postequatorial and 1 long antapical process can be discerned. In a few specimens, however, a further small process is located below 1""", taking the position of an intercalary plate. (Presumably, the intercalary process sometimes fuses with 1""" into a more robust process.)
Dimensions: theca length 68 (53/81) Ám, theca width 59 (50/70) Ám, process length c. 25-30 (19/43) Ám. 150 measurements, 1200 specimens studied.
Emended diagnosis Sarjeant, 1981, p. 103
Cyst spheroidal to broadly ovoidal, two-layered. The periphragm surface may be granulate to shagreenate or may bear striae or rugulae, variably developed. Some 21 processes arise from the periphragm of the complete cyst, each having rootlike proximal extensions of variable length; paratabulation 4", 6"", 0c, 5"""", 0p, 1"""", 0s. The length of the processes is in general around 35-40 % of the shortest cyst diameter; the antapical process, however, is longer and may exceed 50 % of that diameter. They are always fibrous and stout, though with some positional variation in size, but otherwise show considerable variation in form: several are bifurcate, sometimes forking towards their distal end, in other instances dividing so close to their proximal end as to effectively comprise two processes with linked bases. Distally they may be bifid or trifid to multifurcate, with branches of equal to markedly unequal length; the processes themselves, their forks or their branches may be capitate, oblate or foliate. Archaeopyle single-plate precingular (type P), formed by loss of the third precingular paraplate: operculum free.
Dimensions. Length of cyst 64 Ám, breath c. 62 Ám, length of processes 28-36 Ám.
Description. The periphragm wall bears a very variable ornament; sometimes it is faintly granular or punctate, more commonly it is shagreenate, with or without striae or rugulae which may be irregularly distributed, may relate in position in part to process bases (as secondary ,,rootlets" extending out from the rootlike exensions of those bases) or may form an irregular overall areolation extending over a part of, or the whole, surface. The very regular areolate pattern depicted in Klummp"s original drawing (1953, pl.18 fig. 2) appears, however, to be simply an artistic artefact; neither the holotype nor any other specimen examined shows such a pattern.
The processes vary greatly in form. They may bifurcate at about half or at about two thirds length, e.g. processes 4"",5"", 4""" and 5""" of the holotype (Text-fig.1), or so close to their bases that the process linkage is not readily observed, e.g.1", corresponding to the elongate first apical paraplate, in the holotype. In other processes, schism occurs only at the tips and may simulate the spreading fingers of an open hand. All processes are conspicuously fibrous; the number of fibres is consistently much greater than the number of distal branches. In no instance was any distal linkage observed between adjacent processes. The bifid postcingular processes may represent a fusion of these processes with the cingulars; indeed, they are not in the normal situation where postcingulars would be expected, but instead show a displacement toward the anterior.
The antapical process is consistently longest; it is normally or constantly tubiform to slightly tapering. The apical processes are shorter than those of the postcingular series. Cingular and sulcal processes were absent from all specimens examined.
Type Material.16 specimens. Range of Dimensions: Length of cyst 52-76 Ám, length of processes 20-40 Ám.
Davey and Williams, 1966, p. 84
C. inodes has a fibrous body wall, bearing processes which give the reflected tabulation typical of this genus. The variability of processes, noticed by Klumpp, has also been observed in the London Clay forms, especially in the sulcal region. The processes are either hollow, open distally with an ellipsoidal cross-section or taeniate. The process walls of the London Clay specimens are extremely fibrous and appear to be thinner than in the type material, perhaps due to oxidation within the sediment.
Gocht, 1969, p.36-41:
This species has been studied by a number of authors- most recently, by Morgenroth, 1968 and by Davey and Williams. Their respective definitions are very different from one another, but it is commonly agreed that the distribution of processes on the main body of C. inodes is not random, but governed by some rules. My investigations on the Meckelfeld material corroborate this view.
Davey and Williams assume that the archeopyle of Cordosphaeridium is located apically, so that the process on the operculum corresponds to the (only) apical process, and it is followed below by the precingular series with six processes, the cingular series with six, and the postcingular series with six. The antapex would then have one plate; an intercalary process 1p could be present.
In contrast, Morgenroth interprets the archeopyle as a precingular plate, citing as evidence the observation of cingulumlike fimbriae below the archeopyle margin. He counts five apical processes, six precingulars and six postcingulars, six cingular processes, and one antapical process, sometimes with a few additional accessory processes. As will be shown, the Meckelfeld material- ca. 29,000 specimens of C. inodes were prepared- does not fit either of these schemata. Moreover, it gives us an idea of the variability of this species, which affects especially the shape, length, number and arrangement of the processes.
The following general statements apply:
1. Subspecies of C. inodes which occur in Meckelfeld (C. inodes inodes, C. inodes gracilis, and C. inodes robustum) are linked by intermediate forms. Nevertheless, they shall still be treated as subspecies.
2. No equivalent of a cingulum or other aids to orientation were found, but the shape of the archeopyle definitely indicates a precingular location.
3. The number of processes is variable. However, this is not inconsistent with a regular arrangement. The variation affects only particular groups of processes, while others are constant.
On specimens which have not been crushed, the archeopyle is approximately horseshoe- shaped, frequently with rounded corners. Not infrequently, however, a 6-angled type of opening is seen. The broader base, positioned with the cingulum downward, is gently sinuate with a medial apex. The angles on the apical side are usually less distinct. The angulate type of pylome definitely indicates a connection with the original tabulation. This impression is strengthened when we observe notches or- on deformed specimens- inward cracks. The shape of the pylome and notches suggest that this archeopyle is homologous with that of Hystrichosphaera, with the basal notch perhaps representing the medial ridge of the rhomboid cingulum. As stated previously, the number and distribution of processes are regular, but show extensive variation. We must differentiate in this connection between elements which always have the same number and location, and others which are not constant. To describe this situation, the processes may be provisionally designated with letters, differentiating between paired and azygous processes. The plane of symmetry is the sagittal plane. The following processes are constant: the paired elements A, B, and C around the archeopyle, pair D on the hypotheca and the azygous Ap processes (at the apex), P (on the operculum)f and H and E (located toward the ventral side). Lateral processes F and G are usually paired, but sometimes only on one side, or asymmetrical. Opposite the archeopyle there is a series of processes of very variable number. Often there are only four (including E and H), sometimes with a scar or a small spine in the middle. The number six is also frequent, again occasionally with one or more elements in the center. In many samples, forms with thin processes in the ventral region were predominant. Occasionally an additional thin process ("a") occurs also on the dorsal side, directly under the medial notch of the archeopyle margin. The lowest number observed was 19; but there can also be 25 or more. Probably the number usually falls between 20 and 25. Figure 27 shows the constancy of the dorsal processes and the variability of the ventral processes.
It is not easy to reconcile these results with the findings of other authors. The first attempt to link regular arrangements of processes on "hystrichospheres" with dinoflagellate tabulation was made by Evitt, 1963, who at the same time interpreted the processes as elements of the cyst body which were connected with the plates of the surrounding theca (which is not preserved). Davey, Downie, Sarjeant and Williams followed this view. Also Morgenroth, 1968?, as previously mentioned, identified the processes of Cordosphaeridium and other genera with dinoflagellate plates. If we assume the above hypothesis that the archeopyle of Cordosphaeridium is homologous with that of Hystrichosphaera (i.e., the 3"" plate), and if we further consider the fact that the archeopyle process is always located centrally, then it becomes difficult to imagine how the processes could have a regular arrangement without being connected with the arrangement of thecal plates. On the other hand, if we regard the dorsal half of the body, we see that the Gonyaulax-Hystrichosphaera schema (6""-6c-6""") does not apply to the specimens examined here if we take the number of processes to equal the number of plates. Process pairs C and D do not alternate, as we should expect from the rhomboid cingular fields and the postcingulars. Altogether, the number of hypothecal processes is far too small, which is also why Davey and Williams, 1966 moved the archeopyle to the apex. I could not find an ideal solution; however, certain observations point to a possible explanation which seems to be worth pursuing.
The occasional occurrence of a process "a" below the middle of the pylome, at the very spot where it is most certain that a plate was not centered, suggests further comparisons with Hystrichosphaera. For, this observation itself already establishes that there can be sutural ("intertabular") as well as central ("intratabular" Evitt) processes: Two superposed systems of processes can be constructed, one intratabular (as assumed for Hystrichosphaeridium) and the other intertabular (as in Hystrichosphaera). As a rule; one of these two systems remains latent or is completely recessive. If we move the three hypothecal processes D1 + D2 + E in Cordosphaeridium to the intersections formed by a pentangular apical field with the boundaries of the postcingulars, we can quite easily construct a tabulation of the Hystrichosphaera type. The tabulation formula would then be 3", 6"", 6c, 5""", 1"""".
However, the situation in the ventral region remains uncertain; also here, where concentrations of small processes occasionally occur, these processes need not always each correspond to one plate, but may have occurred simultaneously on plate boundaries and in the center. On the other hand, even the longitudinal furrow of Hystrichosphaera is frequently strongly differentiated and divided into more or less open fields. Also, we have to allow for the presence of intercalary ventral plates. Sometimes double processes occur, with the two bases close together. These may result from one process coming apart into its main strands. The main shafts then remain connected only by thin threads which eventually also break. Such cases happen only in C. inodes inodes. As already mentioned, P. Morgenroth, 1968?, who carefully examined 1200 specimens of C. inodes, arrived at different results. Although he too points out the extensive variation, he reports five apical processes and six precingulars as constant. It remains for further research to resolve this discrepancy and perhaps differentiate primitive and derived forms. Of course, among thousands of specimens, deviations and special formations which can not be explained were repeatedly observed. Not all of these can be mentioned. I shall discuss only one: Some specimens have openings which are circular and have a greater diameter than the normal archeopyle. Unfortunately, no single explanation can be given for all such openings, since it was discovered that circular tearing can be caused also by injuries; in such cases, usually there is also a true archeopyle on the same individual. However, the openings in the objects in pl.1, fig.13 and 14, which exhibit narrow fringes, seem to have a biological origin.
C. inodes is the most frequent plankton species in the Early Eocene of Meckelfeld. In many samples, the spectrum of forms is marked decisively by C. inodes, and frequently one can even speak of "inodes assemblages" which also characterize other cores and open exposures in the NW German Eocene. Given the range of variation of C. inodes, its division into subspecies has only limited value;
in some samples, the division is very well attested, while in others it is difficult to separate the forms. In particular, an unbroken chain of transitional forms is observed between C. inodes inodes and C. inodes gracilis.
Cordosphaeridium cf. inodes (Klumpp)
A few specimens from different samples of the upper Late Eocene resemble C. inodes but are striking for the reticulate surface (external membrane) sculpture of the main body and the coarser-fibered process structure. The ends of the processes can be slender and fanlike or deeply slit and coming apart. The process arrangement, at least dorsally, corresponds with that of C. inodes. Ventrally, sometimes there are many thin processes, which may be connected by low basal lists. The reticulate sculpture is not quite as coarse-meshed as that of C. funiculatum Morgenroth. However, also specimens of C. inodes can have coarse-meshed reticulate sculpture, as is shown by a specimen of Eisenack which, judging from its type of processes, would belong, as the author states, to C. inodes gracilis (Eisenack, 1954)
Measurements: Maximal extension 121-157 Ám, main body diameter 61-78 Ám.
Occurrence: Early Eocene- ?Late Eocene.