Hydrolithon corculumis ( Maslov, 1962 ) Braga, Bassi, Zakrevskaya, and Petrovna-Radionova, 2005

Hrabovský, Juraj, 2019, Reproductive phases of Miocene algae from central Paratethys and their bearing on systematics, Acta Palaeontologica Polonica 64 (2), pp. 417-439 : 422-425

Hydrolithon corculumis ( Maslov, 1962) Braga, Bassi, Zakrevskaya, and Petrovna-Radionova, 2005

1978 Lithophyllum corculumis Maslov, 1962 ; Schaleková 1978: 123, pl. 29: 2.

1985 Lithophyllum corculumis Maslov, 1962 ; Schaleková and Čierna 1985: 45, pl. 2: 2.

1985 Lithophyllum corculumis Maslov, 1962 ; Pisera 1985: 104, pl. 24: 1–4.

2013 Lithophyllum sp. ; Hrabovský 2013: 29, pl. 3: h.

Material. —Bi/tetrasporangial plant ( Fig. 3A), NHM B1833/1 (thin section 21510253), early Serravallian reef limestone from Maksymivka, Ukraine (Carpathian Foredeep). Gametophyte bearing spermatangial and carpogonial-carposporangial conceptacles, NHM B1832 (thin section 21510553), the same locality as bi/tetrasporophyte. Carpogonial plant, NHM B1835 (thin section 1849116051), early Langhian, Lopadea Veche, Romania (Transylvania Basin). Other examined specimens are: NHM B1836 (thin section 422), early Serravallian, Devínska Kobyla, Slovakia (Vienna Basin), NHM B1837 (thin section 5100) and NHM B1841 (thin section 29711353), early Serravallian, Rohožník, Slovakia (Vienna Basin), NHM B1840 (thin section 6201), Early Langhian, Kamenica nad Hronom, Slovakia (Danube Basin), NHM B1839/1 (thin section 184911651) and NHM B1839/1 (thin section 184911151), early Langhian, Lopadea Veche, Romania (Transylvania Basin) ( Table 4).

Thin sections with bi/tetrasporophytes from newly collected samples VEGA 29111653 and VEGA 29111553, early Serravallian, Rohožník, Slovakia (Vienna Basin). Schaleková’s (1969, 1973, 1978) material containing H. corculumis

Fig. 3. Coralline alga Hydrolithon corculumis ( Maslov, 1962) Braga, Bassi, Zakrevskaya, and Petrovna-Radionova, 2005 . A. Bi/tetrasporophyte, NHM → B1833/1 (thin section 21510253), early Serravallian, Maksymivka, Ukraine, Carpathian Foredeep.A 1. Portion of the thallus with encrusting growth form and several conceptacles; thallus structure suggests conceptacles protruded slightly above thallus surface during their maturity; note conceptacle on the right with cone shaped pore canal. A 2. Dorsiventral internal organisation and dimerous thallus construction (arrows point to the lateral fusion of cells in adjacent filaments). A 3. Uniporate bi/tetrasporangial conceptacle within dimerous thallus (arrows point to the lateral fusion of the cells in adjacent filaments). A 4. Detail of the pore canal (arrows point to the pore canal filaments, white arrow marks three celled filament, black arrow points to the badly preserved pore canal filament). B. Gametangial-carposporangial plant, NHM B1832 (thin section 21510553), early Serravallian, Maksymivka, Ukraine, Carpathian Foredeep. B 1. Plant growing above the bi/tetrasporic one; primigenous filaments are not seen (white arrow point to the possible trichocyte, black arrow point to the badly preserved trichocyte. B 2. Detail of the spermatangial (white arrowhead) and carposporangial (black arrowhead) conceptacles. Note the flat floor of the spermatangial chamber (arrow point to the roof of the large conceptacle), roof filaments that built the roof and the pore project into the pore canal. C. Carpogonial plant, NHM B1835 (thin section 1849116051), early Langhian, Lopadea Veche, Romania, Transylvania Basin.

C 1. Encrusting growth form with weak projection of carpogonial conceptacle. C 2. Detail of the conceptacle. Note cells forming the roof and the pore canal arrow); cells of adjacent filaments in surrounding thallus are laterally joined with fusions.

+” presence and “–” absence of character. All measurements in μm.

including thin sections VEGA VZ19, VEGA 104, VEGA 5109 from Rohožník, Slovakia, VEGA 406 from Devínska Kobyla, Slovakia, both early Serravallian (Vienna Basin) and thin section VEGA 6201 from Kamenica nad Hronom, Slovakia, early Langhian (Danube Basin).

Description.— Hydrolithon corculumis from Slovakian part of central Paratethys inhabited infra- to circalittoral, algal reefs and soft substrates ( Schaleková 1978; Seneš and Ondrejčíková 1991; Baráth 1992). Specimens from Maksymivka grew on algal reefs and from Lopadea Veche ones were found on large rhodoliths. Species encrust coralline algae mostly. Growth form is encrusting without applanate branches ( Fig. 3A 1 ). Surface is undulate with weak projection of conceptacles.

Thallus is pseudoparenchymatous with dorsiventral internal organisation and dimerous construction consisting two systems of filaments. The primigenous filaments run parallel with the substrate and consist of non-palisade cells ( Fig. 3A 2). Bistratose thalli, built by primigenous and epithallial cells, could develop on short distances at the thallus margins. These parts are considered as young thalli. Cells are rectangular to flattened with H / L ratio 0.8–1.9 and are 9–22 μm H (mean ± SD: 14 ± 2.7 μm) and 7–16 μm L (mean ± SD: 11 ± 2.4 μm) (n = 29). Cells of postigenous filaments are square to rectangular or flattened with L /D ratio 0.5–2.4 ( Fig. 3A 2). Postigenous filaments are up to 19 celled. Cells are 6–26 μm L (mean ± SD: 13 ± 4.2 μm) and 7–15 μm D (mean ± SD: 11 ± 2 μm) (n = 55). Cells of adjacent filaments are laterally joined with fusions but cell fusions are rare ( Fig. 3A 2). Epithallial and meristematic cells were not observed on this specimen but are presented in others. Solitary enlarged cell buried in the thallus is compared with trichocytes ( Fig. 3B 1 ). Two additional badly preserved enlarged cells are probably solitary trichocytes as well ( Fig. 3B 2).

Gametophyte bears two types of conceptacles—smaller triangular spermatangial and larger carpogonial-carposporangial one ( Fig. 3B). Both are developed from initials located peripheral to the fertile area and are not columellated. Spermatangial conceptacle is 58 μm D and 42 μm H. Carpogonial-carposporangial conceptacle is 134 μm D and 64 μm H. Pore canal is cylindrical 68 μm L and 35 μm W. Roof cells protrude into the pore canal ( Fig. 3B 2) .

Carpogonial plant observed in Transylvania Basin material possess non-columellated conceptacle with flat floor developed from cells located peripheral to the fertile area ( Fig. 3C). Conceptacle protrude 51 mμ above thallus surface external diameter reach 297 μm ( Fig. 3C 1 ). Pore canal is cylindrical, 55 μm L and 28–30 μm W at the base. Roof cells protrude into the pore canal ( Fig. 3C 2). Chambers are ellipsoid in shape 86–103 μm D (mean ± SD: 95 ± 0.5 μm) and 40–42 μm H (mean ± SD: 41 ± 1.7 μm) (n = 2). Conceptacle is smaller than Carpathian Foredeep material and is considered as carpogonial.

Bi/tetrasporangial conceptacles roofs are formed by cells perpendicular to the chamber suggesting their development from cells located peripheral and interspersed among sporangial initials ( Fig. 3A). Roof filaments are 2–3 celled. Basal cell or middle cells are often elongated. A roof vanishing is caused by filaments continual growth. Pore canals are more or less cone shaped and bordered by 3 celled filaments ( Fig. 3A). They are not protruding into the pore canal. Pore canals are 33–37 μm L and 24–29 μm D at their base (n = 3). Chambers are lens shaped or hemispherical, 231–308 μm D (mean ± SD: 271 ± 27.1 μm) and 102–130 μm H (mean ± SD: 119 ± 9.8 μm) (n = 6). Central columella was not observed.

Remarks.—Species was designated as Lithophyllum corculumis by Maslov (1962) on the basis Langhian–early Serravallian material collected in the western Ukraine. Later the type material was reassessed by Braga et al. (2005) and species was positioned into the genus Hydrolithon upon lateral cell fusions, dimerous thallus construction and pore canal anatomy ( Braga et al. 2005). However, type of the conceptacles was considered as uncertain either “(tetra) sporangial” or “female/carposporangial” ( Braga et al. 2005). Present results suggest that conceptacles of the type are bi/ tetrasporangial because carpogonial and carposporangial are different in having roof cells projecting into the pore canal while spermatangial conceptacle is small and triangular.

Described specimen differs in having longer cells of postigenous filaments and slightly larger conceptacles than the type reported by Braga et al. (2005) ( Table 4). Nevertheless, important diagnostic features associated with the bi/tetrasporic pore canal and the roof anatomy match the type, hence observed deviations are considered as intraspecific variability. Moreover, comparable vegetative features were reported from Transylvania Basin ( Chelaru and Bucur 2016) and Novohrad Basin ( Schaleková and Čierna 1985).

Examined material fits within the holotype description. Dimerous thallus construction, cells laterally joined with fusions, bi/tetrasporic conceptacle development, solitary trichocytes are consistent with the Hydrolithon diagnosis ( Rösler et al. 2016).

Prior to this study, only two specimens were known from Slovakia ( Schaleková and Čierna 1985; Hrabovský 2013). Both occurrences are Langhian, the former was not found in the collection but the second is consistent with the type diagnosis. Other occurrences are in the Polish part of Carpathian Foredeep ( Pisera 1985; Studencki 1988b). Material from Roztocze Hills ( Pisera 1985) examined in this work prove the species presence in the early Serravallian of Carpathian Foredeep. However, Langhian occurrence was questioned by Braga et al. (2005) because figured specimen does not have cells of adjacent filaments fused. H. corculumis is absent in Czech Republic (Carpathian Foredeep) ( Zágoršek et al. 2012; Hrabovský et al. 2015; present study) and in some Croatian sites of Langhian limestone ( Basso et al. 2008; Sremac et al. 2016).

Geographical and stratigraphic range.—Langhian–early Serravallian (Middle Miocene) of the central Paratethys.

Figures

Fig. 1. Modified geographical and geological map of the studied area with Recent distribution of central Paratethyan deposits, redrawn from Kováč (2000). List of studied sites: 1, Rohožník; 2, Vývrat; 3, Stupava; 4, Devínska Kobyla; 5, Wolfsthal; 6, Müllensdorf; 7, Mikulov; 8, Židlochovice; 9, Blučina; 10, Rebešovice; 11, Telnice; 12, Pratecký Vrch; 13, Holubice; 14, Vyškov; 15, Hluchov; 16, Přemyslovice; 17, Lomnice; 18,- Ochoz; 19, Kralice nad Oslavou; 20, Hostim; 21, Modrý Majer; 22, Čierny Hill; 23, Kamenica nad Hronom; 24, Pavlová; 25, Veľký Pesek; 26,- Sazdice; 27, Štúrovo; 28, Kosihovce; 29, Maksymivka; 30, Lopadea Veche; 31, Weglinek; 32, Zagrody.