GEOLO[KI ANALI BALKANSKOGA POLUOSTRVA BEOGRAD, decembar 2010 71 53–71 ANNALES GÉOLOGIQUES DE LA PÉNINSULE BALKANIQUE BELGRADE, December 2010 DOI: 10.2298/GABP1071053R Observations on Dissocladella annulata (ELLIOTT, 1993) nov. comb. (Calcareous algae, Dasycladales) from the Cenomanian of west Serbia RAJKA RADOIČIĆ1 & FELIX SCHLAGINTWEIT2 Abstract. Based on material from the type area at Tetrebovo in the Zlatibor massif of W Serbia, the Ceno- manian dasycladalean alga originally described as Harlanjohnsonella annulata by ELLIOTT (1968, typified 1993 in: GRANIER & DELOFFRE), is emended and revisited as Dissocladella annulata (ELLIOTT) nov. comb. The evidence of tufts of short secondaries arising at the top of the drop-like primaries allows its transfer to the genus Dissocladella PIA, 1936. This species displays a different degree of skeleton calcification which is de- scribed in detail. The monospecific genus Harlanjohnsonella ELLIOTT becomes invalid, as being a junior syno- nym of Dissocladella. Key words. Dasycladales, Dissocladella annulata (ELLIOTT) nov. comb., systematic taxonomy, Cenoma- nian, Serbia. Апстракт. Дазикладацејску врсту из ценоманских слојева Тетребова (јужни Златибор) описао је EL- LIOTT (1968, типификована 1993 у: GRANIER & DELOFFRE)каоHarlanjohnsonella annulata nov. gen., nov. spec. Преиспитивањем узорака из типског локалитета добијени су детаљнији подаци о грађи ове врсте – до- кументовано је постојање секундарних огранака. Овај податак указао је на њену припадност роду Dis- socladella PIA, а на основу тога моноспецифични род Harlanjohnsonella је инвалидизиран. Дијагноза врсте Dissocladella annulata (ELIOTT, 1968) nov. comb. допуњена је уз детаљне илустрације о структури скелета. Кључне речи: Dasycladales, Dissocladella annulata (ELLIOTT) nov. comb., систематска таксономија, ценоман, Србија. Introduction Based on material sampled at the type locality (RA- DOIČIĆ 1995), from which new thin sections have been In 1968 ELLIOTT described a new dasycladalean ge- prepared, it is documented that the genus Harlan- nus and species as Harlanjohnsonella annulata from johnsonella ELLIOTT represents a younger synonym of transgessive, basal Upper Cretaceous, possibly Ceno- Dissocladella PIA confirming ELLIOTT’s presumption. manian of “Tetrebovo, Dlaglica SE of Zlatibor massif, The scope of the present paper is a taxonomic revision SW Serbia” with the following diagnosis of the genus and detailed illustratation of Dissocladella annulata “Weakly calcified thin-walled tubular and annular (ELLIOTT) nov. comb. dasyclad, with successive verticils showing numerous swollen primaries, the presumed secondaries not be- ing calcified”. The species is typified 1993 in Geological setting GRANIER & DELOFFRE Discussing the relationships, ELLIOTT concluded “that the form now described was, The Cretaceous deposits of the southern (Tetrebo- in fact, a dasyclad of very similar plant morphology to vo, Vis, Fig. 1) and of the central Zlatibor Mountains D. (Dissocladella) savitriae, but more weakly calci- are rare remnants of a Cretaceous (Albian–?Lower fied” and because “there is no direct fossil evidence of Senonian) cover resting upon ultramaphic rocks. First secondary branch-structure the species cannot cor- data on the Cretaceous strata of southern Zlatibor rectly be referred to Dissocladella.” were given by ELLIOTT (1968, “possibly Cenoma- 1 Kralja Petra 38, 11000 Beograd, Serbia. E-mail [email protected] 2 Lerchenauerstr. 167, 80935 München, Germany. E-mail [email protected] 54 RAJKA RADOIČIĆ & FELIX SCHLAGINTWEIT (Fig. 1), in the central Zlatibor and Ravni area in the eastern part of Zlatibor. Regrettably, these data was ignored in the context of geological mapping for the Prijepolje sheet (ĆIRIĆ et al. 1977), and by subsequent researchers (e.g., DIMITRIJEVIĆ et al. 2002: Geology of Zlatibor). The Tetrebovo succession (Figs. 1, 2), overlies pe- ridotites. According to RAMPNOUX (1970, p. 275, fig. 145; 1974, p. 63), it starts with a Lower Cretaceous weathering crust. In detail the succession consists of: – basal conglomerates, – sandy limestones with gastropods, at places lime- stones with “Harlanjohnsonella” annulata ELLIOTT, and, – limestones with Chondrodonta joannae CHOFAT, Radiolites lusitanicus PARONA and R. peroni DOU- VILLE. This succession was ascribed to the Turonian by RAMPNOUX in 1970, afterwards in 1974 to the Ce- nomanian–Turonian as being equal to that one at Rav- ni (East Zlatibor). In the meantime, the rudist lime- stones in the Ravni area, dated as Turonian by PEJOVIĆ & PASIĆ (1958) were revised as being Cenomanian in age (RADOIČIĆ 1995). It should be mentioned, that this Fig. 1. Geological map of the Tetrebovo area, according to does not correspond to the same Ravni succession RAMPNOUX (1970, fig. 145), and Geological map sheet dated as Turonian by RADOIČIĆ. Afterwards, these Prijepolje 1:100000, ĆIRIĆ et al. (1977). Legend: 1, Upper sparsely outcropping Tetrebovo Cretaceous deposits Triassic limestones; 2, Serpentinites; 3, Habzburgites; 4, were sampled only at places (RADOIČIĆ 1995). One of Weathering crust, Lower Cretaceous; 5, Upper Cretaceous the oldest observed beds is represented by a marly limestones (?Albian–Cenomanian). limestone containing gastropods and large specimens of Dissocladella annulata (EL- LIOTT) nov. comb., which are well visible without lens. Up- ward in the section, the lime- stone contains rare benthic foraminifera, the dasycladale- an algae Heteroporella lepina PRATURLON, Terquemella sp. and a few fragments of Disso- cladella annulata. They are followed by limestones with frequent foraminifera, respecti- vely Marssonella turris (D’OR- BIGNY), Rotalia mesogeensis TRONCHETTI, Pseudorhipidio- nia casertana (DE CASTRO), Pseudocyclammina rugosa (D’ ORBIGNY) and Praealveolina cf. iberica REICHEL. Between these beds and youngest ob- serveds skeletal calcarenites (middle-upper Cenomanian), the limestone with relatively Fig. 2. Tetrebovo hill, northern view, Cretaceous deposit are covered by forest. frequent Pseudorhapydionina dubia DE CASTRO is sampled. nian”, based on RAMPNOUX’s data and fossil material) The limestone with Dissocladella annulata con- and RAMPNOUX (1974). The presence of Turonian tains numerous large skeleton fragments, small and strata was documented by RADOIČIĆ (1995) at Vis minute debris, different gastropods, molluscan shells Dissocladella annulata (ELLIOTT, 1993) nov. comb. (Calcareous algae, Dasycladales) from the Cenomanian of west Serbia 55 and rare crustacean fragments, also mentioned by (Pl. 1, Figs. 2, 4; Pl. 2, Figs. 3, 4; Pl. 3, Fig. 7; Pl. 4, Fig. ELLIOTT (1968). In the 25 thin sections studied, only 9; Pl. 5, Figs. 1–6). Only in some specimens, the mem- one specimen of Pseudorhipidionina casertana and a brane of the central stem can be recognized as a dark few small foraminifera were observed. Clearly, Disso- thin micritic line (Pl. 2, Figs. 1, 2, 5; Pl. 3, Fig. 7). The cladella annulata obviously populated shallow-water thin calcareous encrustation of the membrane is rarely environments, probably of low salinity. At the type preserved; it can be recognized only between two pri- locality, the limestone with Dissocladella annulata maries of successive whorls, visible in some sections can be ascribed to the lowermost Cenomanian. (Pl. 1, Fig. 4, arrows; Pl. 3, Fig. 4, left; Pl. 6, Figs. 4, 5). A thin-walled calcareous tube encloses the pores of pri- maries (Pl. 2. Fig. 1), Pl. 3, Fig. 6; Pl. 4, Fig. 1) or more Systematic taxonomy frequently, the thin wall on the surface bears open pores of primaries (Pl. 1, Fig. 1; Pl. 2, Fig. 5; Pl. 3, Figs. 2–5). Division Chlorophyta In rare specimens, the skeleton is dissolved so that it Order Dasycladales PASCHER consists of a thin calcareous layer with irregular exter- Family Triploporellaceae (PIA, 1920) nal surface, on which some parts of the basal calcifica- Tribus Dissocladelleae ELLIOTT, 1977 tion of the primaries can be recognized (Pl. 1, Fig. 3; Pl. Genus Dissocladella PIA, 1936 in: RAMA RAO and 2, Figs. 6, 7). PIA, 1936 The laterals are arranged in a plane; they are rarely (Synonym Harlanjohnsonella ELLIOTT, 1968) slightly overlapping as shown in the specimen illus- trated in Pl. 5, Fig. 8. In successive whorls, laterals do Dissocladella annulata (ELLIOTT, 1968), not alternate regularly, but occasionally alternation nov. comb., revisited can be observed in a few successive whorls. In the Pls. 1–5, Pl. 6, Figs. 1–16 proximal part the primaries display a regular funnel- like form; they communicate with the central stem by 1968 Harlanjohnsonella annulata nov. gen., nov. means of minute pores. In deep tangential sections, sp. – ELLIOTT, p. 494, pl. 93, figs. 1-2, pl. 94, small basal pores can be seen gradually increasing figs. 1-2. from the center to the periphery (Pl. 4, Figs. 1). 1978 Harlanjohnsonella annulata ELLIOTT – BASSO- Transversal sections of primaries are circular in shape ULLET et al., p. 120, pl. 12, figs. 8-9. (Pl. 4, Figs. 1, 2; Pl. 5, Fig. 7, 8). In both, transversal non 1978 Harlanjohnsonella annulata ELLIOTT – LAU- and longitudinal sections of the skeleton, the pores are VERJAT & POIGNANT, p. 123, pl. 2, figs. 1, 5-6. often secondarily enlarged or diminished and/or more 1995 Harlanjohnsonella annulata ELLIOTT – RADOI- or less deformed. ČIĆ, pl. 1, fig. 1. Besides more or less large specimens, the analyzed limestones of Tetrebovo contain numerous small and Material. Twenty-five thin sections from the sam- especially minute fragments of disintegrated skele- ple 022070, R. RADOIČIĆ collection