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Deciphering voids in Dasycladales, the case of Dragastanella transylvanica, a new Lower Cretaceous triploporellacean genus and species from Romania

Published online by Cambridge University Press:  27 May 2021

Filippo Barattolo*
Affiliation:
Dipartimento di Scienze della Terra dell'Ambiente e delle Risorse, Università degli Studi di Napoli “Federico II”, Complesso universitario di Monte Sant'Angelo, via Cintia, 21, 80126 Napoli, Italy
Ioan I. Bucur
Affiliation:
Department of Geology, Babeş-Bolyai University, str. M. Kogălniceanu nr. 1, 400084 Cluj-Napoca, Romania
Alexandru V. Marian
Affiliation:
Department of Geology, Babeş-Bolyai University, str. M. Kogălniceanu nr. 1, 400084 Cluj-Napoca, Romania
*
*Corresponding author

Abstract

Dragastanella transylvanica n. gen. n. sp. is described. Its calcified skeleton contains numerous voids, partly related to the molds of soft parts of the alga, but also related to lack of calcification. Interpretation of these voids, especially their attribution to original structures (e.g., primary lateral versus reproductive organ), has important implications for the taxonomic position of the alga, even at the family level. Examination of key sections that include the boundary between sterile and fertile parts of the alga excludes the occurrence of external reproductive organs. Unusual, paired pores in the outer part of the mineralized skeleton reflect an asymmetry within the whorl, excluding the presence of secondary laterals. The alga is characterized by a cylindrical to club-shaped thallus bearing only phloiophorous primary laterals arranged in whorls and flaring outwards, forming a cortex. Mineralized lenticular reproductive organs containing cysts set in the equatorial plane (Russoella-type gametophores) occur inside primary laterals (cladosporous arrangement of the reproductive organs). These characters support establishment of the new genus Dragastanella. Dragastanella transylvanica n. gen. n. sp. resembles species previously referred to Zittelina (Zittelina hispanica and Zittelina massei) and Triploporella (Triploporella matesina and Triploporella carpatica). Except for Triploporella carpatica, whose mineralized skeleton does not permit confident attribution to either Triploporella or Dragastanella n. gen., the other species must be ascribed to Dragastanella n. gen. Therefore, the following new combinations are proposed: Dragastanella hispanica n. comb., Dragastanella massei n. comb., and Dragastanella matesina n. comb. Despite widely overlapping biometrical measurements, these species can be differentiated by the size and location of their reproductive organs, the pattern of calcification around the primary laterals, and relationships among structural parameters such as the size of laterals, number of laterals per whorl, and distance between whorls.

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Copyright © The Author(s), 2021. Published by Cambridge University Press on behalf of The Paleontological Society
Figure 0

Figure 1. Location of the studied material. (1) Location of the Perşani Mountains within the Carpathian orogen (small rectangle indicated with yellow arrow); (2) geological map of the central-southern part of the Perşani Mountains; A–G, outcrops of Urgonian limestone; outcrop A corresponds to the location of the Fântâna area (modified after Popescu, 1970).

Figure 1

Figure 2. Succession of the upper Aptian limestone at Fântâna with ranges of the most important microfossils; M, mudstone; W, wackestone; F, floatstone; P, packstone; G, grainstone; R, rudstone; B, boundstone. Red circle, type horizon.

Figure 2

Figure 3. Dragastanella transylvanica n. gen. n. sp. Different structural interpretations of the voids (pores and empty spaces) based on a tangential oblique section through the lower part of the biomineralized skeleton. In the analysis presented here: (1) voids are interpreted as pores (molds of primary laterals) and empty spaces as lack of calcification between them; (2) pores are interpreted as combinations of molds of primary laterals and external gametophores; empty spaces occur between them; (3) pores are partly interpreted as false pores (molds of primary laterals) and empty space between the cystophores; empty spaces occur between them; (4) tangential oblique section (thin section PSM 901-104, specimen N122). Presumed shape shown by dashed line. Scale bar represents 1.0 mm.

Figure 3

Figure 4. Dragastanella transylvanica n. gen. n. sp.; various structural interpretations of the alga. (1) Cladosporous primary lateral containing cystophores; (2) primary lateral bearing a single lateral gametophore (goniosporate type, as in primitive Dasycladaceae, e.g., Bakalovaella); (3) primary lateral bearing several lateral gametophores (goniosporate type, as in Bornetellaceae). Colors as in Figure 3; central stem in gray. Scale bar represents 1.0 mm.

Figure 4

Figure 5. Dragastanella transylvanica n. gen. n. sp.; interpretation of pores in oblique section. (1) Oblique section (thin section PSM 901-104, specimen N089); (2) interpretative drawing of (1). Yellow, calcified skeleton; light gray/gray, pores of subsequent whorls (without cystophores). Presumed shape shown by dashed line. Scale bar represents 1.0 mm.

Figure 5

Figure 6. Dragastanella transylvanica n. gen. n. sp.; interpretation of sections. (1) Drawing of the oblique section (Fig. 5.1 = Fig. 11.6); w1, intercept of the innermost whorl; w2, intercept of the outermost whorl; (2) axial view of the corresponding part (lower part of the thallus) with w1 and w2 positions; gray dotted line, intercept of the oblique section (1); (3) transverse view (sector) of w1 with the intercept in (1); (4) transverse view (sector) of w2 with the intercept in (1); (5) axial view of the central lateral l1 with the hypothesis of two orders of laterals; (6) axial view of the central lateral l1 with the hypothesis of cladosporous primary lateral; (7) axial view of the second lateral at right l2 with the hypothesis of two orders of laterals; (8) axial view of the second lateral at right l2 with the hypothesis of cladosporous primary lateral in an asymmetrical whorl; dashed line, intercept of the oblique section (1). Black: mineralized skeleton. Scale bar represents 1.0 mm.

Figure 6

Figure 7. Examples of asymmetrical whorls. (1) Batophora oerstedii whorl amid the sterile and fertile regions; only one primary lateral out of five bears gametophores (drawing in transverse view from Berger, 2006, p. 55, fig. 22); (2) Cymopolia mayaense oblique section in the lower part of an article; the primary lateral at left bears the gametophore (black arrow), the corresponding lateral at right (white arrow) lacks the gametophore (Selandian, environs of Sarakhs, NE Iran, DiSTAR-BA4249.1). Scale bars represent (1) 1.0 mm; (2) 0.5 mm.

Figure 7

Figure 8. Dragastanella transylvanica n. gen. n. sp., upper Aptian, central-southern part of the Perşani Mountains near Fântâna village (Braşov County, Romania). (1) Axial section, PSM 901-16, specimen N013, holotype; notice the tapered bottom (laterals reducing in size downwards), bottom laterals orthogonal to inclined, vertical laterals at top, and the outer tracts that are usually shifted downwards with respect to the primary lateral axis; (2) oblique section cutting the top and bottom of the thallus, PSM 901-37, specimen N033, paratype; bottom apparently not tapered, with laterals orthogonal to gently inclined upward, outer tract aligned along the lateral axis, occurrence of eight-shaped pores (third whorl from the bottom); (3) oblique section crossing the bottom of the thallus (inner ellipse of the section is eccentric, shifted downwards with respect to the outer ellipse), PSM 901-37, specimen N031, paratype; bottom tapered with sterile laterals orthogonal to gently inclined upward; (4) fragment of a calcareous skeleton in axial section, showing the tapered bottom of the thallus, PSM 901-62, specimen N053, paratype; (5) oblique section across the tapered bottom of the thallus, PSM 901-84, specimen N073, paratype; (6) transverse-oblique section, PSM 901-44, specimen N039, paratype; mineralization extends up to the cortex; (7) oblique section, PSM 901-15, specimen N012, paratype; calcareous skeleton extends up to the middle tract of laterals; (8) longitudinal section, PSM 901-48, specimen N043, paratype; bottom not tapered; (9) transverse section, PSM 901-73, specimen N063, paratype; notice the lateral fusion of pores (annular channel) and the swollen inner end of primary laterals resembling a countersink; (10) tangential section, PSM 901-116, specimen N092, paratype; occurrence of thin walls between the pores of the same whorl; eight-shaped pores are visible at the top of the photo. All scale bars represent 1.0 mm.

Figure 8

Figure 9. Dragastanella transylvanica n. gen. n. sp., upper Aptian, central-southern part of the Perşani Mountains near Fântâna village (Braşov County, Romania). (1) Oblique section, PSM 901-17, specimen N014, paratype; calcareous skeleton coating only the inner and the middle tracts of the primary laterals; (2) oblique section through the lower part of the thallus (sterile laterals at bottom), PSM 901-21, specimen N018, paratype; calcareous skeleton reaches the cortex, first whorl in the bottom is sterile, second whorl is asymmetrical (last, but one pore on the right is fertile); (3) oblique section though top of the thallus (inner cavity apparently shifted upward, as in Fig. 9.4), PSM 901-18, specimen N015, paratype; annular, uncalcified channel as in the specimen in Figure 9.5; (4) oblique section though the upper part of the thallus, PSM 901-40, specimen N035, paratype; calcareous skeleton reaches to the cortex, outer tract aligned along the lateral axis; (5) oblique section, PSM 901-82, specimen N072, paratype; mineralized skeleton not reaching the outer tract, occasional interverticillar arrangement of the cystophores, shifted beyond the laterals; (6) oblique section, PSM 901-137, specimen N107, paratype; thin mineralized wall between pores of the same whorl (top of the picture); (7) oblique section, PSM 901-24, specimen N021, paratype; notice oblique, uncalcified channels (bottom of the picture), (8) tangential-oblique section, PSM 901-41, specimen N036, paratype; occurrence of oblique channels and vertical package of laterals between alternated whorls, external cortex. All scale bars represent 1.0 mm.

Figure 9

Figure 10. Dragastanella transylvanica n. gen. n. sp., upper Aptian, central-southern part of Perşani Mountains near Fântâna village (Braşov County, Romania). (1) Oblique section, PSM 901-136, specimen N106, paratype; notice the remnants of mineralization between whorls (fertile middle tract of the primary laterals); (2) oblique section through the upper part of the thallus, PSM 901-125, specimen N097, paratype; primary laterals apparently form a sort of inner cortex (regular hexagonal meshes close to the central stem) in addition to the outer cortex (bottom of picture); the outer tract of the lateral is shifted downwards; (3) oblique section cutting the lower part of the thallus, PSM 901-24, specimen N021, paratype; bottom sterile laterals orthogonal to inclined upward; (4) tangential section, PSM 901-46, specimen N041p, paratype; regular hexagonal meshes close to the central stem, as in Figure 10.2, remnants of mineralization between alternating whorls, superior arrangement of the cystophores; (5) transverse section, PSM 901-123, specimen N095, paratype, the swollen inner end of primary laterals looks countersunk; (6) oblique section through the top of the thallus, PSM 901-142, specimen N112, paratype, orthogonal laterals in the lower part; (7) oblique section crossing the lower part of the thallus, PSM 901-150, specimen N116, paratype; the outer tract of the lateral is aligned along the main lateral axis (not shifted downwards); (8) transverse section, PSM 901-72, specimen N062, paratype, laterals are swollen inward like a countersink (top of the picture), their distal parts are not preserved. All scale bars represent 1.0 mm, except (4) = 0.5 mm.

Figure 10

Figure 11. Dragastanella transylvanica n. gen. n. sp., upper Aptian, central-southern part of Perşani Mountains near Fântâna village (Braşov County, Romania). (1) Tangential section, PSM 901-124, specimen N096, paratype; cystophores are inside (superior type) and outside the laterals (marginal) in the lower and upper part of the thallus, respectively; (2) oblique section, PSM 901-149, specimen N115, paratype; primary laterals are distally conspicuously flared outwards (cortex); (3) sub-tangential section, PSM 901-115, specimen N091, paratype; note how primary laterals (outer tract) distally shift downwards; (4) transverse section, PSM 901-88, specimen N077, paratype; laterals are clearly swollen outwards (upper part of the picture, cortex); (5) oblique section through the lower, partly sterile, part of the thallus, PSM 901-57, specimen N049, paratype; notice sterile whorls (bottom of the picture); (6) oblique section, PSM 901-113, specimen N089, paratype; see the eight-shaped pores (bottom of the picture) and the outer tract of primary laterals shifted downwards (right). All scale bars represent 1.0 mm.

Figure 11

Figure 12. Dragastanella transylvanica n. gen. n. sp., upper Aptian, central-southern part of the Perşani Mountains near Fântâna village (Braşov County, Romania). (1) PSM 901-124, detail of specimen N096 (see Fig. 11.1, upper part), paratype; peripheral arrangement of the cystophores; (2) PSM 901-147, specimen N113, paratype; cystophores generally cut along the axis; (3) PSM 901-152, detail of specimen N117, paratype; cystophores generally cut along the equatorial plane; (4) PSM 901-124, detail of specimen N096 (see Fig. 11.1, lower part), paratype; superior arrangement of the cystophores; (5) PSM 901-131, detail of specimen N102, oblique section (lower part), paratype; interverticillar arrangement of cystophores; (6) PSM 901-137, detail of specimen N108, transverse oblique section (right side), paratype; cystophores mainly set inside the laterals. Scale bars represent 0.5 mm in (1, 4–6) and 0.25 mm in (2, 3).

Figure 12

Table 1. Dragastanella transylvanica n. gen. n. sp. Table of main biometrical parameters: d, inner diameter; D, outer diameter; l, length of the primary lateral; piw, whorl width of the first tract of the primary lateral; pw, whorl width of the primary lateral (maximum diameter); h, height between whorls; w, number of laterals in a whorl; cystophore Eq., equatorial diameter of the cystophores; cystophore Ax, axial diameter of the cystophores; cyst diameter, axial diameter of cysts. Values of h and w from oblique sections are mathematically inferred. All dimensions are in millimeters.

Figure 13

Figure 13. Dragastanella transylvanica n. gen. n. sp. (1) Reconstruction of the alga in axial section; black, calcified skeleton; gray, soft parts; (2) axial view of the soft parts (green).

Figure 14

Figure 14. Dragastanella transylvanica n. gen. n. sp.; reconstruction of the alga in transverse view. (1) Sector of a whorl in transverse section; black, extracellular and intracellular (cystophore) calcification; (2) sector of a whorl in transverse section; black, extracellular and intracellular (cystophore) calcification; gray, soft parts; (3), upper view of whorl, soft parts in green; (4) cystophores in equatorial section (up) and in axial section (down), usually containing 3–5 gametangia (cysts). Scale bar represents 1.0 mm (1–3) and 0.2 mm in (4).

Figure 15

Figure 15. Algal structures compared. (1) Axial and (2) tangential section of Dragastanella transylvanica n. gen. n. sp.; (3) axial and (4) tangential section of Dragastanella hispanica n. comb.; (5) axial and (6) tangential section of Dragastanella massei n. comb.; (7) axial and (8) tangential section of Dragastanella matesina n. comb.; (9) axial and (10) tangential section of Triploporella carpatica. Extracellular calcification in yellow, intracellular calcification in black, presumed shape shown by dashed line. All figures: scale bar represents 1.0 mm.

Figure 16

Figure 16. Primary (1–3) and secondary (4, 5) positions of cystophores in triploporellid species. (1) Superior; (2) internal; (3) peripheral; (4) interverticillar; (5) marginal. Intracellular calcification shown in black; presumed shape shown by dashed line.

Figure 17

Table 2. Biometrical dimensions compared. Symbols are the same as Table 1. Values in parentheses are estimated from original photographs. All dimensions are in millimeters.