Back
Samlandia paucitabulata
Fig. 10, Pl. 1, figs. 1–21, Pl. 2, figs. 1–8.
? 2000 Samlandia mayi McMinn 1988 – Slimani: pl. 10, figs. 12, 13.
? 2001a Samlandia mayi McMinn 1988 – Slimani: pl. 2, fig. 14.
2012 Samlandia mayi McMinn 1988 – Aleksandrova, Beniamovskii, Vishnevskaya, Zastrozhnov: pl. VII, figs. 8, 9 (only).
? 2013 Samlandia carnarvonensis McMinn 1988 – Surlyk, Rasmussen, Boussaha, Schiøler, Schovsbo, Sheldon, Stemmerik, Thibault: fig. 9F.
Derivation of name: From Latin paucus – few, little, and Latin tabulatus – boarded, plated, with reference to the tabulation, which is not completely distinguishable under a transmitted light microscope.
Holotype: Pl. 1, figs. 1–8; Piotrawin quarry, sample P9; slide MWGUW ZI/90/P9/0 l; slide co-ordinates: 8.8/4.4, EF: T26/0; housed at the S. J. Thugutt Geological Museum, Faculty of Geology, University of Warsaw, Warsaw, Poland. The holotype is mounted in dorsal view (Pl. 1, figs. 1–3); before permanent mounting it was also photographed in left lateral (Pl. 1, figs. 4, 5) and ventral (Pl. 1, figs. 6–8) views.
Type locality and horizon: Piotrawin quarry, central Poland (51°05'37"N, 21°48'06"E), 2 m above the base of the outcrop; mid-upper Campanian (low “Inoceramus” altus Zone).
Diagnosis: Gonyaulacacean (cribroperidinioid) proximate cysts; holocavate, thick-walled, with distinct and continuous ectophragm. Ectocoel cavations delineated by network of continuous muri enclosing pillow-like spaces, commonly with accessory supporting structures. Cysts weakly paratabulate; plate arrangement partly reflected by distribution of muri and ectophragm features, commonly obscured by accessory structures supporting ectophragm. Archeopyle precingular, type 1P (3").
Description: Proximate cysts, intermediate in size and robust in appearance; subspheroidal, oblate (antero-posteriorly compressed), ovoidal, or polyhedral in shape (roughly circular to subpolygonal in outline), with very small (c. 1–4 μm long) apical horn occasionally present. Holocavate; cyst wall consists of homogeneous endophragm (c. 0.5–1 μm thick), alveolate periphragm (c. 0.5–1 μm thick), and spongy to homogeneous and continuous ectophragm (c. 1 μm thick), with finely, densely granular outer surface. Peri- and ectophragm connected by network of distinct alveolate muri (c. 2–5 μm wide, 8–12 μm high), enclosing numerous ectocoel cavities of more or less uniform height; muri in sutural and intratabular positions (plate areas covered by one or more ectocoel cavities). Ectocoel cavities often internally outlined by very thin (c. 0.2–0.5 μm) homogeneous membrane with smooth surface (Pl. 2, fig. 8). Accessory and discontinuous alveolate muri or pillars arising from periphragm occur commonly inside ectocoel cavities. Tabulation cribroperidinioid (L-type ventral organization, sexiform antapex, and dextral torsion of hypocyst) corresponding to formula 4', 6'', 6c, 6''', 1p, 3–?5s, 1'''' (Fig. 10), roughly reflected by shapes of pillow-like ectocoel cavations, and indicated by linear (sutural) depressions of ectophragm, commonly accompanied by lines of perforations occurring above the muri marking the plate boundaries. Archeopyle precingular (type 1P), formed by loss of plate 3''; operculum usually free, occasionally attached.
Dimensions. Holotype: Endocyst (length x width): 47 x 42 μm, total diameter (length x width): 75 x 71 μm, maximal height of ectocoel: 14 μm. Range: Endocyst length: 38 (44.7)51 μm, endocyst width: 40(45.5)51 μm, total length (without apical horn): 57(66.3)79 μm, total width: 57(66.5) 75 μm, ectocoel height: 9(12.1)16 μm, apical horn length: 1 (2.2)4 μm (15 specimens measured). Isolated operculum (length x width) = 35(36.6)38 x 32(33.3)36 μm (3 opercula measured).
Discussion: Due to its thick-walled holocavate structures and distinct, continuous ectophragm, Samlandia paucitabulata sp. nov. has a robust appearance. Under TLM, the alveolate periphragm structure may appear to be reticulate, distinctly granulate, or verrucate (Pl. 1, figs. 1, 4, 6). The ectophragm is supported by a dense network of thick muri, and does not tend to be folded or waved, as in the other species of the genus. Under TLM, the boundaries between particular ectocoel cavities are commonly visible as two parallel lines (Pl. 1, figs. 1, 2, Pl. 2, fig. 1). They represent homogeneous membranes that internally outline the holocavations, separated by alveolate muri (Pl. 2, fig. 8). The accessory muri or pillars (see Pl. 1, figs. 2, 4, 11) usually occur within the ectocoel cavities that occupy larger plates (e. g., precingular, postcingular, and antapical plates), while cingular, sulcal, and other smaller plates generally lack additional supporting structures. Consequently, the interpretation of tabulation in specimens possessing numerous accessory muri may be confusing. The cyst tabulation is also reflected by linear depressions in the ectophragm, commonly accompanied by lines of perforations occurring above the plate boundaries (Pl. 1, figs. 18–21, Pl. 2, fig. 3). However, the perforations are visible only under SEM.
Remarks: Samlandia mayi McMinn 1988 of Aleksandrova et al. (2012), from the basal upper Campanian of the Volga Region (Russian Federation), shows a strong resemblance to S. paucitabulata sp. nov. It is thick-walled, robust in appearance, and has a distinct ectophragm, thicker and more regular in outline than that characteristic of S. mayi. Furthermore, the wall of this specimen has a reticulate or distinctly granular appearance, and bears regularly arranged muri separating the ectocoel spaces (the cingulum is the most evident). Consequently, it is synonymized with S. paucitabulata sp. nov. Samlandia carnarvonensis McMinn 1988, of Surlyk et al. (2013), from the upper Campanian of Denmark, also bears a close resemblance to S. paucitabulata sp. nov. Although this specimen does not reveal a clear segmentation into the paratabulate holocavations, it is quite similar in the nature of its thick ectophragm and the wall ornamentation (similar specimens have also been found in the material studied here). Samlandia mayi McMinn 1988 of Slimani (2000, 2001a) from the upper Campanian of the Netherlands, with its partially tabulate ornament, resembles closely S. paucitabulata sp. nov.
Comparison: In overall morphology, Samlandia paucitabulata sp. nov. is most comparable to S. mayi McMinn 1988. Both species have distinct ectocoel cavations (the ectophragm is relatively distant from the inner cyst wall), but differ in regards to their wall structures and the appearance of their ectophragms. In S. mayi, the inner wall is homogeneous to finely spongy in structure and distinctly thicker than the ectophragm, giving the cyst wall a smooth appearance. The thin and fragile ectophragm in S. mayi (Pl. 2, figs. 9–11) is supported by unevenly distributed discontinuous muri and processes, arising from the periphragm and connected distally by arch-shaped trabeculae, rendering the ectophragm irregularly wavy. Furthermore, S. mayi lacks any signs of tabulation other than its archeopyle. Consequently, S. paucitabulata sp. nov. can easily be distinguished from S. mayi under TLM by its reticulate wall appearance, partially sutural alignment of wall ornament (cingulum is the most commonly demonstrated), thicker ectophragm, more regular outline, and distinct appearance of the ectophragm. Samlandia carnarvonensis McMinn 1988 (see Pl. 2, figs. 12–14), like S. mayi, is atabulate. It is additionally distinguished from S. paucitabulata sp. nov. by its smaller size and cyst ornamentation (the inner wall ornamentation in S. carnarvonensis consists of a dense network of low nontabular crests with short processes). The ectophragm of S. carnarvonensis is thinner and irregularly wavy, and lies close to the cyst inner wall. S. paucitabulata sp. nov. also lacks a well-developed apical horn, in contrast to S. carnarvonesis.
Recorded stratigraphic range: Middle upper Campanian, “Inoceramus” altus Zone (Piotrawin section). Other occurrences: Russian Federation: Volga Region, Borehole 13, sample 92 (basal upper Campanian) – as Samlandia mayi in Aleksandrova et al. (2012, pl. VII, figs. 8, 9).
Other possible occurrences: Denmark: Stevns-1 borehole, sample 394.93 m (upper Campanian) – as Samlandia carnarvonensis in Surlyk et al. (2012, fig. 9F). The Netherlands: Beutenaken quarry, sample 13 (upper Campanian) – as Samlandia mayi in Slimani (2000, pl. 10, figs. 12, 13, 2001a, pl. 2, fig. 14).
? 2000 Samlandia mayi McMinn 1988 – Slimani: pl. 10, figs. 12, 13.
? 2001a Samlandia mayi McMinn 1988 – Slimani: pl. 2, fig. 14.
2012 Samlandia mayi McMinn 1988 – Aleksandrova, Beniamovskii, Vishnevskaya, Zastrozhnov: pl. VII, figs. 8, 9 (only).
? 2013 Samlandia carnarvonensis McMinn 1988 – Surlyk, Rasmussen, Boussaha, Schiøler, Schovsbo, Sheldon, Stemmerik, Thibault: fig. 9F.
Derivation of name: From Latin paucus – few, little, and Latin tabulatus – boarded, plated, with reference to the tabulation, which is not completely distinguishable under a transmitted light microscope.
Holotype: Pl. 1, figs. 1–8; Piotrawin quarry, sample P9; slide MWGUW ZI/90/P9/0 l; slide co-ordinates: 8.8/4.4, EF: T26/0; housed at the S. J. Thugutt Geological Museum, Faculty of Geology, University of Warsaw, Warsaw, Poland. The holotype is mounted in dorsal view (Pl. 1, figs. 1–3); before permanent mounting it was also photographed in left lateral (Pl. 1, figs. 4, 5) and ventral (Pl. 1, figs. 6–8) views.
Type locality and horizon: Piotrawin quarry, central Poland (51°05'37"N, 21°48'06"E), 2 m above the base of the outcrop; mid-upper Campanian (low “Inoceramus” altus Zone).
Diagnosis: Gonyaulacacean (cribroperidinioid) proximate cysts; holocavate, thick-walled, with distinct and continuous ectophragm. Ectocoel cavations delineated by network of continuous muri enclosing pillow-like spaces, commonly with accessory supporting structures. Cysts weakly paratabulate; plate arrangement partly reflected by distribution of muri and ectophragm features, commonly obscured by accessory structures supporting ectophragm. Archeopyle precingular, type 1P (3").
Description: Proximate cysts, intermediate in size and robust in appearance; subspheroidal, oblate (antero-posteriorly compressed), ovoidal, or polyhedral in shape (roughly circular to subpolygonal in outline), with very small (c. 1–4 μm long) apical horn occasionally present. Holocavate; cyst wall consists of homogeneous endophragm (c. 0.5–1 μm thick), alveolate periphragm (c. 0.5–1 μm thick), and spongy to homogeneous and continuous ectophragm (c. 1 μm thick), with finely, densely granular outer surface. Peri- and ectophragm connected by network of distinct alveolate muri (c. 2–5 μm wide, 8–12 μm high), enclosing numerous ectocoel cavities of more or less uniform height; muri in sutural and intratabular positions (plate areas covered by one or more ectocoel cavities). Ectocoel cavities often internally outlined by very thin (c. 0.2–0.5 μm) homogeneous membrane with smooth surface (Pl. 2, fig. 8). Accessory and discontinuous alveolate muri or pillars arising from periphragm occur commonly inside ectocoel cavities. Tabulation cribroperidinioid (L-type ventral organization, sexiform antapex, and dextral torsion of hypocyst) corresponding to formula 4', 6'', 6c, 6''', 1p, 3–?5s, 1'''' (Fig. 10), roughly reflected by shapes of pillow-like ectocoel cavations, and indicated by linear (sutural) depressions of ectophragm, commonly accompanied by lines of perforations occurring above the muri marking the plate boundaries. Archeopyle precingular (type 1P), formed by loss of plate 3''; operculum usually free, occasionally attached.
Dimensions. Holotype: Endocyst (length x width): 47 x 42 μm, total diameter (length x width): 75 x 71 μm, maximal height of ectocoel: 14 μm. Range: Endocyst length: 38 (44.7)51 μm, endocyst width: 40(45.5)51 μm, total length (without apical horn): 57(66.3)79 μm, total width: 57(66.5) 75 μm, ectocoel height: 9(12.1)16 μm, apical horn length: 1 (2.2)4 μm (15 specimens measured). Isolated operculum (length x width) = 35(36.6)38 x 32(33.3)36 μm (3 opercula measured).
Discussion: Due to its thick-walled holocavate structures and distinct, continuous ectophragm, Samlandia paucitabulata sp. nov. has a robust appearance. Under TLM, the alveolate periphragm structure may appear to be reticulate, distinctly granulate, or verrucate (Pl. 1, figs. 1, 4, 6). The ectophragm is supported by a dense network of thick muri, and does not tend to be folded or waved, as in the other species of the genus. Under TLM, the boundaries between particular ectocoel cavities are commonly visible as two parallel lines (Pl. 1, figs. 1, 2, Pl. 2, fig. 1). They represent homogeneous membranes that internally outline the holocavations, separated by alveolate muri (Pl. 2, fig. 8). The accessory muri or pillars (see Pl. 1, figs. 2, 4, 11) usually occur within the ectocoel cavities that occupy larger plates (e. g., precingular, postcingular, and antapical plates), while cingular, sulcal, and other smaller plates generally lack additional supporting structures. Consequently, the interpretation of tabulation in specimens possessing numerous accessory muri may be confusing. The cyst tabulation is also reflected by linear depressions in the ectophragm, commonly accompanied by lines of perforations occurring above the plate boundaries (Pl. 1, figs. 18–21, Pl. 2, fig. 3). However, the perforations are visible only under SEM.
Remarks: Samlandia mayi McMinn 1988 of Aleksandrova et al. (2012), from the basal upper Campanian of the Volga Region (Russian Federation), shows a strong resemblance to S. paucitabulata sp. nov. It is thick-walled, robust in appearance, and has a distinct ectophragm, thicker and more regular in outline than that characteristic of S. mayi. Furthermore, the wall of this specimen has a reticulate or distinctly granular appearance, and bears regularly arranged muri separating the ectocoel spaces (the cingulum is the most evident). Consequently, it is synonymized with S. paucitabulata sp. nov. Samlandia carnarvonensis McMinn 1988, of Surlyk et al. (2013), from the upper Campanian of Denmark, also bears a close resemblance to S. paucitabulata sp. nov. Although this specimen does not reveal a clear segmentation into the paratabulate holocavations, it is quite similar in the nature of its thick ectophragm and the wall ornamentation (similar specimens have also been found in the material studied here). Samlandia mayi McMinn 1988 of Slimani (2000, 2001a) from the upper Campanian of the Netherlands, with its partially tabulate ornament, resembles closely S. paucitabulata sp. nov.
Comparison: In overall morphology, Samlandia paucitabulata sp. nov. is most comparable to S. mayi McMinn 1988. Both species have distinct ectocoel cavations (the ectophragm is relatively distant from the inner cyst wall), but differ in regards to their wall structures and the appearance of their ectophragms. In S. mayi, the inner wall is homogeneous to finely spongy in structure and distinctly thicker than the ectophragm, giving the cyst wall a smooth appearance. The thin and fragile ectophragm in S. mayi (Pl. 2, figs. 9–11) is supported by unevenly distributed discontinuous muri and processes, arising from the periphragm and connected distally by arch-shaped trabeculae, rendering the ectophragm irregularly wavy. Furthermore, S. mayi lacks any signs of tabulation other than its archeopyle. Consequently, S. paucitabulata sp. nov. can easily be distinguished from S. mayi under TLM by its reticulate wall appearance, partially sutural alignment of wall ornament (cingulum is the most commonly demonstrated), thicker ectophragm, more regular outline, and distinct appearance of the ectophragm. Samlandia carnarvonensis McMinn 1988 (see Pl. 2, figs. 12–14), like S. mayi, is atabulate. It is additionally distinguished from S. paucitabulata sp. nov. by its smaller size and cyst ornamentation (the inner wall ornamentation in S. carnarvonensis consists of a dense network of low nontabular crests with short processes). The ectophragm of S. carnarvonensis is thinner and irregularly wavy, and lies close to the cyst inner wall. S. paucitabulata sp. nov. also lacks a well-developed apical horn, in contrast to S. carnarvonesis.
Recorded stratigraphic range: Middle upper Campanian, “Inoceramus” altus Zone (Piotrawin section). Other occurrences: Russian Federation: Volga Region, Borehole 13, sample 92 (basal upper Campanian) – as Samlandia mayi in Aleksandrova et al. (2012, pl. VII, figs. 8, 9).
Other possible occurrences: Denmark: Stevns-1 borehole, sample 394.93 m (upper Campanian) – as Samlandia carnarvonensis in Surlyk et al. (2012, fig. 9F). The Netherlands: Beutenaken quarry, sample 13 (upper Campanian) – as Samlandia mayi in Slimani (2000, pl. 10, figs. 12, 13, 2001a, pl. 2, fig. 14).