Calamitean Cones and Their In Situ Spores from the Pennsylvanian Limnic Basins of the Czech Republic

This paper describes the in situ spores of the Calamospora type, macerated from sixty-one specimens of calamitean cones belonging to sixteen species of genera, such as the Palaeostachya, Macrostachya, Calamostachys, and Huttonia from the Pennsylvanian Czech Republic period, specifically from the Moscovian/Kasimovian ages (i.e., Duckmantian-Stephanian). The in situ spores were compared to twenty dispersed species of Calamospora. The majority of spores were microspores; however, some cones yielded both micro- and megaspores. Morphological variations of the in situ spores, including the diameter, labrum, contact area, ontogenetic stages, and secondary folds of the exine, are described, including their importance for the classification of calamospores. The relationships of Elaterites, Pteroretis, Vestispora, and some monopseudosaccate spores are discussed. All Paleozoic Calamospora-producing parent plants are summarized.


Introduction
Sphenophytes are an important group of both extant and extinct plants.The first specimens come from the Devonian period [1][2][3] but were never abundant.The "Golden age" for sphenophytes was the Carboniferous period, especially in Pennsylvanian times when arborescent forms reached up to 30 m [4].After the Permian period, their diversity gradually declined until recent times.We know of only one recent genus, Equisetum Linnaeus, which has fifteen to eighteen species [4].Some phylogenetic analyses [5] suggest that sphenophytes and ferns can be a monophyletic group [6].Paleozoic sphenophytes are divided into two main groups: calamiteans and sphenophyllaleans.All Paleozoic calamiteans produced spores of the Calamospora type.Sphenophyllaleans can be palynologically divided into 6-7 groups, and only one of them produced Calamospora microspores [7].
Calamospora Schopf et al. is a spore genus consisting of mio-and megaspore species with long stratigraphical ranges from the Silurian [8] to Tertiary periods [9].It is the morphologically simplest spore type, with circular to oval amb, simple trilete rays, and laevigate exine.Many morphologically simple spore types were produced by parent plants of different affinities, including Calamospora [7].This is the reason why Calamospora has no stratigraphical and palaeoecological significance.
The genus was established [8] with the species type C. hartungiana Schopf et al.The number of classification criteria is low [10,11].These include the contact area, length of rays of the trilete mark, labrum, number, size, shape, position of the secondary folds of the exine, and diameter.Biologically, calamospores were both male and female spores that cannot be distinguished morphologically but only by their diameter; 200 µm is an artificial "boundary" for the recognition of calamospores into male and female spores [7].However, this boundary size does not always correspond with the biological function of calamospores.The main producers of Calamospora calamitean cones were the genera Calamostachys Schimper, Palaeostachya Weiss, Macrostachya Schimper, and Paracalamostachys

Material and Methods
The specimens labeled E are housed in the National Museum, Prague, Czech Republic.Some specimens are from the collection of S. Opluštil, Faculty of Sciences, Prague, Czech Republic.A Nikon Eclipse BX51 light microscope was used for the study of palynological slides.Digital photomicrographs of all the in situ microspores are stored in the Laboratory of Palaeobiology and Palaeoecology, Institute of Geology v.v.i., Academy of

Material and Methods
The specimens labeled E are housed in the National Museum, Prague, Czech Republic.Some specimens are from the collection of S. Opluštil, Faculty of Sciences, Prague, Czech Republic.A Nikon Eclipse BX51 light microscope was used for the study of palynological slides.Digital photomicrographs of all the in situ microspores are stored in the Laboratory of Palaeobiology and Palaeoecology, Institute of Geology v.v.i., Academy of Sciences, Prague.Spores were recovered by dissolving small portions of sporangia with the aid of nitric acid for 24-40 h and in KOH for 1 h.The majority of spores were mounted in glycerine jelly for a direct microscopic examination.A minority of them were coated with gold and prepared for SEM observation.The terms used for the descriptions of the in situ spores were obtained from the latest edition of the Glossary of Pollen and Spore Terminology [20].In situ, the spores were compared according to the system of classification of dispersed spores [21][22][23].A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 3 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers.The size range is 34 (65) 119 µm (Table 3).The contact area (Figure 5b-d    A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach half of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 6g-k).The size range is 51 (70) 89 µm.The labrum is sometimes developed (Figure 6g,i).The in situ microspores can be compared to the dispersed miospore species Calamospora cf.pedata, C. cf.microrugosa, and C. cf.straminea.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach half of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 6g-k).The size range is 51 (70) 89 µm.The labrum is sometimes developed (Figure 6g,i).The in situ microspores can be compared to the dispersed miospore species Calamospora cf.pedata, C. cf.microrugosa, and C. cf.straminea.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 7b-d,j-o).The size range is 60 (112) 141 µm (Table 4).The contact area and labrum are up to 6 µm in size and sometimes developed (Figure 7c,h,j,l,n,o).Sometimes, fragments of the perispore can occur on the surface of the exine (Figure 7d).The in situ microspores can be compared to the dispersed miospore species Calamospora hartungiana, C. cf.hartungiana, C. falkenbergensis Venkatachala & Bharadwaj, and C. mutabilis.It is possible that some spores that are classified as Calamospora falkenbergensis, C. cf.hartungiana, and C. mutabilis, with size ranges of 82 to 152 µm, may be megaspores.A description of the in situ spores is as follows: Trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 7q-v).The size range is 34 (65) 95 µm (Table 5).The labrum is 2-4 µm broad and is sometimes developed (Figure 7v).The in situ microspores can be compared to the dispersed miospore species Calamospora braviradiata, C. minuta, C. cf.pedata, and C. cf.microrugosa.A description of the in situ spores is as follows: Trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 7q-v).The size range is 34 (65) 95 µm (Table 5).The labrum is 2-4 µm broad and is sometimes developed (Figure 7v).The in situ microspores can be compared to the dispersed miospore species Calamospora braviradiata, C. minuta, C. cf.pedata, and C. cf.microrugosa.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores (Figures 9j and 10a,b) is up to 2 µm and the megaspores (Figures 9h,i,k, 10c-e,i,j, and 11b-f) are up to 3 µm thick.The rays of the trilete mark reach a third to three-quarters of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figures 9j, 10a,b,e, and  11e,d).The size range (Table 6) of the microspores is 54 (76) 125 µm, and the megaspores are 156 (265) 372 µm (Table 7).The contact area and labrum are 2-4 µm in size and sometimes developed.The in situ microspores can be compared to the dispersed miospore species Calamospora mutabilis, C. cf.pedata, and C. cf.liquida.Megaspores are classified as Calamospora sp.due to their large diameters.A description of the in situ spores is as follows: The trilete are subcircular microspores.The size range is 55 (69) 108 µm.The laevigate exine is up to 2 µm thick.The labrum is 2-4 µm in size (Figure 9b,e).Rays of the trilete mark reach a third to two-thirds of the radius.The microspores are poorly preserved and only as fragments and incomplete specimens (Figure 9c,d,f), probably due to oxidation of the rock.This is the reason why in situ spores can be only described as the Calamospora type.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores (Figures 9j and 10a,b) is up to 2 µm and the megaspores (Figures 9h,i,k, 10c-e,i,j, and 11b-f) are up to 3 µm thick.The rays of the trilete mark reach a third to three-quarters of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figures 9j, 10a,b,e, and 11e,d).The size range (Table 6) of the microspores is 54 (76) 125 µm, and the megaspores are 156 (265) 372 µm (Table 7).The contact area and labrum are 2-4 µm in size and sometimes developed.The in situ microspores can be compared to the dispersed miospore species Calamospora mutabilis, C. cf.pedata, and C. cf.liquida.Megaspores are classified as Calamospora sp.due to their large diameters.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a quarter to a half of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figures 12a-h and 13c-j).The size range of the microspores is 54 (94) 126 µm, and the megaspores are 180 (357) 684 µm (Table 8).The labrum is 2-4 µm broad, and the dark contact areas (Figure 12a,d,f) are sometimes developed (Figures 12e and 13a).The in situ microspores can be compared to the dispersed miospore species Calamospora microrugosa, C. cf.mutabilis, C. pallida, C. cf.pallida, C. cf.pedata, C. breviradiata, and C. hartungiana; the megaspores are classified as Calamospora sp.due to their large diameters (up to 684 µm).A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 14a-f).The size range is 51 (73) 88 µm.The labrum is 2-4 µm broad and is sometimes developed.The in situ microspores can be compared to the dispersed miospore species Calamospora cf.hartungiana.Some spores are 54 (75) 94 µm large and are enveloped in a very thin monopseudosaccate layer (Figure 14c-f A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 14a-c,i,j,m-o).The size range is 45 (60) 83 µm (Table 9).Sometimes, the outer perispore-like layer envelopes the central body of the Calamospora type (Figure 14k,l,p).The in situ microspores can be compared to the dispersed miospore species Calamospora microrugosa, C. pallida, and C. pedata.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figures 15q and 16c,d).The size range is 30 (61) 110 µm in diameter (Table 10).The labrum is 2-4 µm broad and is sometimes developed.Some specimens have irregular fragments of perisporial tissue (Figures 15o,p,r and 16a-d).The in situ microspores can be compared to the dispersed miospore species Calamospora microrugosa, C. cf.pedata, C. straminea, and C. breviradiata.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figures 15q and 16c,d).The

Moscovian (Bolsovian).
A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 17c,d,h,j,l).The size range is 48 (62) 89 µm in diameter.The in situ microspores can be compared to the dispersed miospore species Calamospora cf.microrugosa.Some specimens are 49 (65) 99 µm in size and are enveloped by a thin monopseudosaccate layer and can resemble some forms of the miospore genera Auroraspora, Remysporites, Perotrilites, Phyllothecotriletes, or even Diaphanospora, and some others have irregular fragments of perisporial tissue (Figure 17e,h,i,k,l).A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach half to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 17n-q).The size range is 34 (85) 137 µm.The labrum is 2-4 µm broad and is sometimes developed (Figure 17n,o).The in situ microspores can be compared to the dispersed miospore species Calamospora cf.liquida and C. cf.pedata.
A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach half to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 17n-q).The size range is 34 (85) 137 µm.The labrum is 2-4 µm broad and is sometimes developed (Figure 17n,o).The in situ microspores can be compared to the dispersed miospore species Calamospora cf.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to a half of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 18b-f).The size range is 52 (58) 70 µm.The in situ microspores can be compared to the dispersed miospore species Calamospora breviradiata.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach a third to a half of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 18b-f).The size range is 52 (58) 70 µm.The in situ microspores can be compared to the dispersed miospore species Calamospora breviradiata.
A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach three-quarters of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 18i,j).The size range of the microspores is 45 (67) 82 µm, and the megaspores are (Figure 18h) 610 (703) 815 µm.The labrum is 2-4 µm broad and is sometimes developed.The in situ microspores can be compared to the dispersed miospore species Calamospora cf.liquida and C. cf.flexilis, and the megaspores are classified as Calamospora sp.due to their large diameters.
Huttonia Sternberg 1837 Huttonia spicata Sternberg 1837 Figure 19 Life 2024, 14, x FOR PEER REVIEW 28 of 35 A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 2 µm thick.The rays of the trilete mark reach three-quarters of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 18i,j).The size range of the microspores is 45 (67) 82 µm, and the megaspores are (Figure 18h) 610 (703) 815 µm.The labrum is 2-4 µm broad and is sometimes developed.The in situ microspores can be compared to the dispersed miospore species Calamospora cf.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.The laevigate exine of the microspores is up to 1-4 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers (Figure 19d,f,g).The size range of the microspores is 66 (84) 114 µm, and the megaspores are (Figure 19g) 115 (166) 240 µm.The labrum is 2-4 µm broad and is sometimes developed.The in situ microspores can be compared to the dispersed miospore species Calamospora cf.breviradiata, C. cf.pedata, and the megaspores are of the Calamospora laevigata type.Some specimens are enveloped in a thin monopseudosacccate exine layer (Figure 18e) and can resemble some forms of miospore genera Auroraspora, Remysporites, Perotrilites, or even Diaphanospora.

Morphological Criteria
The majority of morphological features are important for the classification of dispersed calamospores, but some others, like the thickness of the exine and the sculpture, are not as significant.Some species are morphologically closely similar, and it is possible that they can be synonymous.We can divide the dispersed calamospores into a few main morphological groups, e.g., by contact area, by contact area and labrum, and only by the labrum.
Only a few authors have described a significant number of calamitean cones and their in situ Calamospora micro-and megaspores [11,15,24].

Diameter
The size range given for every dispersed Calamospora species is not a significant criterion for their natural classification.In every Calamospora in situ population, the size range is variable, with specimens ranging from about 20-30 µm to more than 100 µm.One of the morphological species groups shares the same features and may be the only criterion for distinguishing it among different species of dispersed spore species [11].The average size range of the in situ Calamospora microspores is 24 (75.02)181 µm, and 147.0 (399.15)815.0 µm for the Calamospora megaspores.The average difference (i.e., among the smallest and largest spores in a slide) in size is 40 µm.Dispersed calamospores are assigned to miospore and megaspore species based on their size, but the arbitrary size criterion of at least 200 µm for megaspores need not always correspond with their biological function.For example, the spore population from Palaeostachya elongata (E3631) is divided into two size groups.The smaller group ranges in size from 35 to 55 µm, and the larger group ranges from 105 to 150 µm in diameter.Similarly, in another specimen of P. elongata (E1121), spores fall into two size categories: the first category includes spores 35 to 55 µm in diameter, and the second group includes spores ranging from 85 to 140 µm in diameter.The definition of 200 µm or more for megaspores is artificial and may not apply to many Calamospora megaspores.The diameter of calamospores can be influenced by stages of maturity.It seems that calamitean cones matured gradually from apical to basal sporangia.The difference in the diameter for Calamospora from apical and basal sporangia is 5 (12) 16 µm, with an extreme example of cones of Palaeostachya elongata, where it is 79 µm.The difference between relatively immature and mature specimens was about 91 µm on average for the megaspores.

Contact Area
Usually, all spores in a Calamospora in situ population either do or do not have a contact area.This could mean that the occurrence of the contact area may be a reliable criterion for the classification of dispersed calamospores.However, the number of in situ microspores with a contact area is higher in apical than in basal microsporangia, i.e., it implies that this morphological feature may be related to different degrees of maturity because the contact area means that the exine at the proximal pole is thickened and the thickness of the exine may be influenced by stages of maturity.The diameter of the contact area is usually equal to the length of the rays of the trilete marks or maybe sometimes slightly shorter.Sometimes, under SEM, the contact area can be seen to be slightly elevated, i.e., it is slightly thickened proximally.We know (minimally) of ten Pennsylvanian Calamospora species with contact areas with a size range from 34 to 146 µm and with the length of the trilete marks being a third to two-thirds of the radius.This indicates that the size of the contact area is not an easy way to distinguish among Calamospora dispersed species.

Length of Rays of the Trilete Mark
The length of the rays of the trilete mark of a majority of Calamospora specimens is from a third to three-fourths of the radius.Almost all dispersed calamospores fit into this size range.Only a few dispersed Calamospora species have longer rays of the trilete mark, e.g., Calamospora liquida.

Labrum
The presence or absence of a labrum need not be a constant morphological feature.Some spores from one sporangium possess a labrum, but some other spores from the same sporangium do not.A labrum is usually seen well using SEM.Only a few dispersed Calamospora species are defined with a labrum, e.g., C. flava and C. elliptica.

Secondary Folds of Exine
We can imagine Calamospora spores in sporangium like small circular balloons without any folding, only with trilete marks on the exine surface.Due to the fossilization (adpression specimens, not petrifactions), the spore body is compressed, and the thin laevigate exine becomes folded.Different types of folding are purely occasional and not biological.Many dispersed Calamospora species are distinguished based on different foldings.It shows the arbitrary character of the classification of dispersed Calamospora species.For example, C. pedata is typified by one major secondary fold that covers about a half of the spore body; C. flexilis is typical by its folds parallel with the rays of the trilete mark, and C. mutabilis, C. straminea, C. parva, and C. breviradiata have folds parallel with the margins of the spores.

Fragments of Tapetal Tissues
Sometimes, it is possible to observe calamospores with various fragments of probable tapetal tissues on the exine surface.These fragments have irregular sizes, shapes, thicknesss, and numbers.Sometimes, they cover the majority of the exine surface, and sometimes, only a small part.These forms are not comparable to any dispersed miospore species and are more likely related to the ontogenetic stages.

Elaterites
Spores of the genus Elaterites Wilson are very rare in the dispersed record.The genus was established [30] for spores with three elaters enveloping a central body of the Calamospora type.These microspores are very rarely reported [30][31][32][33].Seventeen species of genera, such as the Calamocarpon Baxter, Calamostachys, Mazostachys, Palaeostachya, Pendulostachys Good, Pothocites Paterson, and Weissistachys Rothwell & Taylor, yielded spores of the Elaterites type from mainly petrified (Table 11) [9,21] and adpression [15] specimens.The size range of these microspores is 38 (78) 280 µm, and almost all of them are 38-112 µm in diameter, except for those isolated from Calamostachys americana Arnold, which is unusually large (140-280 µm) [10].Some authors [10,12,34] propose that all calamiteans produced microspores of the Elaterites type.We have studied hundreds of palynological slides with in situ Calamospora populations in different stages of ontogeny, macerated from sixty specimens of calamitean cones, and we have never seen any elaters or any elater-like structures or their fragments.It is evident that there is a group of calamitean cones that produced spores of the Elaterites type, but the majority of them yielded only spores of the Calamospora type.Some authors [10,12,24] have proposed that Vestispora represents an ontogenetic stage of Calamospora.The authors of [35] excluded this theory based on some main points, and the authors confirmed their conclusions.

Classification of In Situ Spores
Vestispora is characterized by a homogeneous outermost exine layer and small circular operculum lying above the proximal pole of the central body of the Calamospora type.Elaterite spores lack an operculum, and there is always a space among three elaters, i.e., the outer layer is not homogeneous.Elaters of Elaterites originate from a small triangular area on the distal pole, i.e., opposite to the proximal surface with a small circular operculum.Anything resembling such a triangular distal structure has never been observed on the Calamospora spores described herein.The structure of Elaterites is monotonous, but the sculpture of Vestispora is variable, including laevigate, foveolate, costate, and primary and secondary reticulate.
The second point is that Vestispora and Calamospora spores were produced by different plants.Vestispora was not produced by any calamiteans.The major Vestispora producer was one group of sphenophyllaleans [33].Another small group of sphenophyllaleans produced calamospores but only Calamospora and not Calamospora and Vestispora together.Calamospora ranges from the Devonian to the Cenozoic, whereas Vestispora-producers range from the Brigantian to late Kasimovian.As a consequence, almost all Vestisporaproducing sphenophyllaleans are good stratigraphical markers, but calamitean spores are not.Elaterites have an even shorter stratigraphical range, ranging through only a part of the Pennsylvanian [36].Almost all Vestispora-producing sphenophyllaleans are good stratigraphical markers [37], but calamiteans are not.Elaterites have an even shorter stratigraphical range, only a part of the Pennsylvanian [35].
When in situ, Elaterites are reported only from coal-ball calamitean cones and not from adpressions.The only roughly similar spore structures are hygroscopic elaters of the recent Equisetum spores, which show that their ultrastructure is different.The sporoderm of Equisetum spores has an endospore, exospore, perispore, and bi-layered elaters [38], but the Elaterites are only bi-layered, and elaters have three layers.
Vestispora spores have a circular laevigate central body with trilete marks and outer exospores with a circular operculum.Sometimes, in palynological slides with in situ Vestispora, it is possible to observe various degrees of mechanical damage in the exospores and that the central body is of the Calamospora type.However, Vestispora is not a relatively immature Calamospora because we have never observed any ontogenetic stages of Vestispora.
Table 11 shows all the Elaterites producing calamitean plants.

Parent Plants
The main Calamospora producers are calamitean cones, especially the genera Calamostachys, Palaeostachya, and Macrostachya.Minor producers of Calamospora are the genera Pothocites, Paracalamostachys Weiss, Huttonia, Weissistachys, Cingularia Weiss, Pendulostachys, and Calamocarpon.Non-calamitean producers are sphenophyllaleans (Table 12) and noeggerathialeans.Sphenophyllaleans and calamiteans are closely related.The noeggerathialean genus Discinites K. Feistmantel produced micro-and megaspores of the Calamospora type and Noeggerathiaestrobus O. Feistmantel-only Calamospora megaspores (Table 12).Calamospora was produced by several parent plant species of different affinity [7], but its main producers were Pennsylvanian calamiteans.The first record of the in situ spores was interpreted as Calamospora (Calamospora atava (Naumova) McGregor and C. pannucea Richardson) or Retusotriletes type) and is known as the zosterophyll species Sawdonia acanthotheca Gensel et al. [41].Note that Retusotriletes is curvaturate and, therefore, distinct from Calamospora and that most of the zosterophylls possess Retusotriletes-type spores.Calamospora-type spores, which are reported in some zosterophylls, such as S. acanthotheca, may be immature.From the Paleozoic plants of possible lycophyte affinity, we know only one record of an in situ Calamospora, Mississippian genus Eleutherophyllum Stur [42].

Conclusions
A comparison of hundreds of palynological slides with in situ populations, isolated from sixty-one specimens of Pennsylvanian calamitean cones belonging to sixteen species of four genera, allows the definition of morphological variations of in situ Calamospora.The classification of dispersed Calamospora is purely arbitrary because all morphological criteria, including the diameter, thickness of exine, number, shape, position, and size of the secondary folds of the exine, as well as the length of rays of the trilete marks, are variable within one in situ Calamospora population.Some features are variable, and others are related to different ontogenetic stages.
The calamitean cones matured gradually from the base to the apex, as demonstrated by the different diameters of spores and a more frequent occurrence of contact areas on the spores isolated from basal and apical sporangia.The calamitean cones were bisporangiate, and an arbitrary size criterion for the division of micro-and megaspores (200 µm) may not be biologically meaningful.Some cones yielded spores with a bimodal size distribution, so even though the larger spores were less than 200 µm, they probably represent megaspores because the size in these populations exhibits a bimodal curve.
There is no evidence that Elaterites and Vestispora are ontogenetic stages of Calamospora, as demonstrated by the morphological and stratigraphical differences.However, it is evident that some Paleozoic calamitaleans produced not only Calamospora but also the Elaterites spores.
The majority of Paleozoic Calamospora producers were calamitean cones, mainly the genera Calamostachys, Palaeostachya, and Macrostachya.Sphenophyllaleans were a minor source of Calamospora.Some noeggerathialeans also produced Calamospora.

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Figure 3 . 35 Figure 4 .
Figure 3. Palaeostachya ettingshausenii Kidston.(a) General view of the whole specimen No. E3624, Mayray Mine near Kladno, Kladno-Rakovník Basin, Moscovian.Natural size.(b) Megaspore of the Calamopora type.×100.(c-f) Microspores of the Calamospora type.(e) Note one major fold of exine covers the spore body.(f) Note a secondary fold of exine parallels the margin of the spore.All ×500.Material: The specimens are from the S. Opluštil's collection and are as follows: Nos.935 and 1451 are from the Tuchlovice Mine, Kladno-Rakovník Basin, Czech Republic, Bashkirian (Upper Duckmantian); E2414, E3624, E3626, E2412, and E3623 are from the Mayray Mine, Kladno; E3618 is from the Max Mine, Kladno; E3635 is from the Ronna Mine, Kladno; and E3596 is from the Břasy locality.All are from the Kladno-Rakovník Basin.The following specimens are from the Intra-Sudetic Basin as follows: E3622 is from the Maria-Julia Mine near Třemošín, Kasimovian (Stephanian); and E2500 is from the Žacléř locality, with an unknown stratigraphic position.A description of the in situ spores is as follows: The trilete spores are circular, subtriangular, or oval in amb.Two kinds of spores probably represent the microspores (Figures2d-i,k,l, 3c-f, and 4c,d,f-i) and megaspores (Figures2b,c, 3b, and 4a,b).The laevigate exine of the microspores is up to 4 µm thick, and that of the megaspores is 6-9 µm thick.The rays of the trilete mark reach a third to two-thirds of the radius.Secondary folds of the exine possess variable sizes, shapes, positions, and numbers.Three size categories of the in situ spores were recognized (Table2): the first with a size range of 44 (71) 171 µm

Figure 8 35 Figure 8 Figure 8 .
Figure8shows the bimodal distribution of the in situ spores isolated from Palaeostachya elongata.

Table 2 .
The size of the in situ spores of Palaeostachya ettingshausenii Kidston.

Table 2 .
The size of the in situ spores of Palaeostachya ettingshausenii Kidston.

Table 3 .
Size of the in situ spores of Paleostachya distachya.

Table 4 .
Size of the in situ spores of Palaeostachya elongata.

Table 5 .
Size of the in situ spores of Palaeostachya gracillima Weiss.

Table 7 .
Diameters of the in situ megaspores of the Calamospora type isolated from different portions (basal, middle, and apical) of the cone of Macrostachya carinata (Germar) Zeiller.

Table 8 .
Size of the in situ spores of Calamostachys germanica Weiss.

Table 9 .
Size of the in situ spores of Calamostachys longibracteata Němejc.

Table 10 .
Size of the in situ spores of Calamostachys tuberculata (Sternberg) Jongmans.

Table 11 .
Parent plants produced spores of the Elaterites type.