Schlagintweit.indd 27 � AB STRA CT The new genus Gosavisiphon with the type-species Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998, tentatively referred to the Udoteaceae, is described from the Late Cretaceous (Middle/Late Cenomanian-Santonian) of the Branderfl eck Formation and the Lower Gosau Subgroup of the Northern Calcareous Alps (Austria, Germany). It is a plurimillimetric to pluricentimetric marine, hard-substrate dwelling macroalga, with membraneous and partly fused plates and an internal siphonaceous construction but lacking a real medullary zone. Although some thallus de- tails are still unknown, Gosavisiphon gen. nov. can, from a strictly morphological point of view, directly be compared with the Late Palaeozoic and Upper Triassic phylloid algae. Gosavisiphon gen. nov. is the fi rst fossil record of a platy siphonal alga in the Cretaceous, since the Late Triassic Ivanovia triassica REID. The monotypic taxon is most prob- ably endemic to the Northern Calcareous Alps where it dwelled in protected, terrestrially infl uenced lagoonal envi- ronments attaching to hard substrates, (metazoan skeletons, rudistid shells). Based on fi ndings of the cylindrical Halimeda? aff. johnsoni PAL and another taxon described as Halimeda sp. with typically fl attened ovate segments, some considerations on the segment-morphological phylogenetic evolution of Halimeda LAMOUROUX are pro- vided. Halimeda species with discoidal-fl attened segments, that can morphologically be compared with extant spe- cies, are not known prior to the Turonian. Forms possessing cylindrical segments date further back, but can not di- rectly be compared morphologically with modern counterparts, thus placing doubts on the existence of long-lasting methusalemi species by uniting extant and fossil species, as proposed by both botanists and palaeontologists in re- cent times. Keywords: Calcareous algae, taxonomy, Bryopsidales, Halimedaceae, Udoteaceae, phylloid algae, Phylogeny, Upper Cretaceous, Northern Calcareous Alps Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga (Udoteaceae?) from the Late Cretaceous of the Northern Calcareous Alps, (Austria and Germany), with affi nites to Late Palaeozoic and Late Triassic phylloids � Felix Schlagintweit Lerchenauerstr. 167, D-80935 München, Germany; (ef.schlagintweit@t-online.de) doi: 10.4154/gc.2010.02 Geologia Croatica 63/1 27–53 14 Figs. 4 Tabs. Zagreb 2010 Geologia CroaticaGeologia Croatica Geologia Croatica 63/1Geologia Croatica 28 calcareous algae were reported from different localities (e.g. SCHLAGINTWEIT & WEIDICH, 1991; SCHLAGINTWEIT, 1992). The subsequent marine transgression affecting the higher nappe units started during the Turonian with the tec- tonosedimentary cycle of the Gosau Group that unconform- ably overlies mainly Triassic and Jurassic sediments. The Alpine Gosau Group can roughly be subdivided into a lower subgroup with neritic shelf lithologies, and an upper sub- group consisting of deeper water facies (WAGREICH & FAUPL, 1994) (Figs. 1A–B). From Turonian to Campanian times, a variegated, mixed siliciclastic-carbonate succession up to more than 2000 metres thick accumulated in a wide 1. INTRODUCTION In the area of the Northern Calcareous Alps (NCA), Late Ju- rassic to Early Cretaceous convergence and nappe stacking were followed by extensional exhumation and subaerial ex- posure of large parts of the orogen (e.g. RATSCHBACHER et al., 1989). Within the northern part of the NCA, namely the Lechtal Nappe, the transgressive sedimentary cycle of the Branderfl eck Formation started in the Lower Cenoma- nian with breccias, conglomerates and orbitolinid sandston- es, followed succesively by deeper water lithologies (e.g. GAUPP, 1982; WEIDICH, 1984). From Turonian marls, oli- stolites of Late Cretaceous shallow water limestones with Fi gu re 1: A) Simplifi ed tectonic map of the Eastern Alps with the major occurrences of the Gosau Group (in black) (see WAGREICH & FAUPL, 1994). Oc- currences of calcareous algae described in the present paper (yellow circles; for the distribution of individual taxa see Table 1): 1 Krumbachalm, Branden- berg, Tyrol; 2 Pletzachalm, Tyrol; 3 Lattengebirge, Salzburg, 4 Eisenbach, Lake Traunsee, Upper Austria 5 Rußbach-Pass Gschütt-Gosau (Gosau type-area), 6 Weißwasser-Unterlausa, Lower Austria, 7 Gams, Lower Austria. B) Lithostratigraphic subdivision of the Gosau Group of the type area (from WAGREICH & DECKER, 2001); asterix marks the position of the fi ndings of Gosavisiphon in the area of Gosau (locality Hofergraben) and Pass Gschütt-Rußbach (local- ity Randobach). C) The village of Gosau (780 m altitude) with the Dachstein Mountains in the background; view towards the south. White arrow points to the Hofergraben. A B C Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 29 discovered in various outcrops of the Lower Gosau Sub- group (Fig. 1A, from west to east). The last taxon was also observed in olistolites of the Branderfl eck Formation. Brief informations on geographical setting, microfacies and asso- ciations of the algal-bearing samples and stratigraphy are given for each locality. Occurrences of the described taxa are summarized in Table 1. 2.1. Lower Gosau Subgroup Krumbachalm area, Brandenberg (locality 1 in Fig. 1). The outcropping limestones of the Lower Gosau Subgroup are located at the northern part of the Brandenberg Gosau, a larger erosional remnant of the Gosau Group located in Ty- rol, about 10 km west of Wörgl (e.g. Fig. 2 in SANDERS, 1998). Microfacies and associations: Halimeda? aff. johnsoni PAL occurs in bioclastic packstones with corals, rudistids, echinoderms, gastropods, calcareous algae (green algae and red algae), including Permocalculus (Pyrulites) theresien- steinensis SCHLAGINTWEIT & SANDERS, and benthic foraminifera (textulariids, and arenaceous encrusting taxa). The Krumbachalm area is also the type-locality of Acan- thochaetetes? krumbachensis (SENOWBARI-DARYAN et. al., 2004). Stratigraphy: Upper Turonian to Coniacian (SANDERS, 1998 and SANDERS & PONS, 1999 for details). spectrum of terrestrial to neritic palaeoenvironments (Lower Gosau Subgroup; WAGREICH & FAUPL, 1994). Deposition of the Lower Gosau Subgroup was terminated, from Santo- nian to Campanian times, by deepening into bathyal to abys- sal depths (WAGREICH & FAUPL, 1994). The area around the village of Gosau (Upper Austria) and Russbach (Salzburg) represents the type locality of the Gosau Group (Fig. 1C). The lithostratigraphic division of the Gosau type area still used to- day is that from WEIGEL (1937) with modifi cations in the last decades (WILLE-JANOSCHECK, 1966; WEISS, 1977; WAGREICH, 1988; WAGREICH & DECKER, 2001) (Fig. 1B). The present occurrences (Fig. 1A) only represent the ero- sional remnants of a former wider distribution; preservation is often due to faulting or deposition in synse di mentary active small basins (WAGREICH & DECKER, 2001). In the Lower Gosau Subgroup, calcareous algae, mainly Dasycladales and Halimedaceae, were reported from la go onal limestones, rudistid limestones, and marly limestones, inter- calated within marly successions of Middle Turonian to Up- per Santonian age (e.g. HÖFLING, 1985; SCHLAGINT- WEIT, 1991, 1992, 2004; SCHLAGINTWEIT & LOBITZ ER, 2003a). For an inventory of calcareous green algae of the Lower Gosau Subgroup see SCHLAGINTWEIT (2004). The alga Halimeda paucimedullaris was described by SCHLAG- INTWEIT & EBLI (1998) from the Pletzachalm section in the Sonnwend Mountains, Tyrol. It also occurs in the Lat- tengebirge (Salzburg), Weißwasser-Unterlausa (Lower Au- stria) and Pass Gschütt-Gosau (e.g. SCHLAGINTWEIT & LOBITZER, 2003b). New material from the Gosau of Gams, Styria, and the reinvestigation of material already published, especially that from the Hofergraben near Gosau, resulted in the recognition of morphological and microstructural details that differ suffi ciently from the genus Halimeda LAMOUR- OUX, to warrant establishment of a new genus of the order Bryopsidales with the generic name Gosavisiphon gen. nov. and the new combination Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI), described in this paper. 2. SAMPLE LOCALITIES AND MATERIAL STUDIED Halimeda sp., Halimeda? aff. johnsoni PAL and Gosavisi- phon paucimedullaris (SCHLAGINTWEIT & EBLI), were Fi gu re 2: Stratigraphic distribution of Halimeda? johnsoni PAL, Halimeda sp. and Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI) in the Late Cre- taceous Lower Gosau Subgroup of the Northern Calcareous Alps supplemented with literature data. It is most likely that Halimeda sp. has a larger strati- graphic distribution, than the two Middle-Late Turonian occurrences (see Tab. 1). The dashed dark-grey line in Halimeda? johnsoni refers to a possible synonymy with Boueina pygmaea PIA. For comparison, the distribution of the "phylloid algae" and the genus Halimeda are indicated (see Tab. 3 and de- tails in the text). Table 1: Summary of the investigated sample localities with respect to the occurrence of the described calcareous algae. Species Lo ca lit ie s Kr um ba ch al m Pl et za ch al m La tt en be rg Ei se nb ac h Ra nd ob ac h H of er gr ab en W ei ßw as se r N ot h- Kl am m Halimeda? aff . johnsoni � Halimeda sp. � � Gosavisiphon paucimedullaris � � � � � � � Geologia Croatica 63/1Geologia Croatica 30 Pletzachalm (locality 2 in Fig. 1). The Pletzachalm section near Kramsach (Fig. 1 in SCHLAGINTWEIT & EBLI, 1998, for exact location), Tyrol (Austria), was fi rst described litho- logically in detail by LEISS (1988). The micropalaeontological content (benthic foraminifera, calcareous algae) was studied by SCHLAGINTWEIT (1991, 1992), SCHLA GINT WEIT & EBLI (1998) and SCHLAGINTWEIT & SANDERS (2008), revealing several new taxa, mainly calcareous algae. Micro- facies and associations: Gosavisiphon gen. nov. occurs in marly limestones that are intercalated within a series of marls, with layers of gastropods and coaly plant remains, followed up the section by a rudistid biostrome. Gosavisiphon gen. nov. is as- sociated mainly with calca reous algae including Dissocladella? pyriformis SCHLAGINTWEIT, Neomeris mokragorensis RADOIČIĆ & SCHLA GINTWEIT, Oroseina pletzachensis SCHLAGINTWEIT & EBLI, Halimeda sp., and benthic fo- raminifera Vidalina hispanica SCHLUMBERGER (and other miliolids), cuneolinids and Tetrataxiella? fl oriformis SCHLA- GINTWEIT & SANDERS. Stratigraphy: The age of the series containing Gosavisiphon gen. nov. below the rudistid limestones is Late Turonian. Lattengebirge (locality 3 in Fig. 1). From this locality, the new taxon was reported for the fi rst time as Halimeda sp. by HÖFLING (1985) from the so-called Krönner Reef. The biocoenosis of the lagoonal "epibenthic udoteacean- dasycladacean association" and its adjacent reefal palaeoen- vironments were schematically reconstructed by HÖFLING (1985) (see also MOUSSAVIAN et al., 1993). The outcrops occur at the northern side of the Lattengebirge, southeast of Bayerisch Gmain near Bad Reichenhall (Germany); topo- graphic map no. 8243 Reichenhall (for exact location see Fig. 1 in KLINGHARDT, 1942). Microfacies and association: Gosavisiphon gen. nov. oc- curs within marly wackestones referred to a back-reef la- goonal environment (HÖFLING, 1985). Stratigraphy: The Krönner Reef was considered to be Santonian in age (KLINGHARDT, 1942; HÖFLING, 1985); Strontium isotope data revealed a mid Coniacian age (STEU- BER, 2001), which is the same age obtained for the rudistid limestones of Weißwasser (see below). Eisenbach, Lake Traunsee (locality 4 in Fig. 1). The Eisenbach Gosau occurrence is located at the eastern side of Lake Traunsee in the Upper Austrian Salzkammergut, ÖK 25, sheet 67 Grünau im Almtal. The samples with Gosavisiphon gen. nov. belong to the type material (type locality) of the dasycladale Thyrsopore- lla eisenbachensis (see Fig. 1 in SCHLAGINTWEIT & LO- BITZER, 2003a). Microfacies and associations: Gosavisiphon nov. gen. was found in marly limestones; wackestones with coaly plant remains, gastropods, ostracods and Thyrsoporella eisenba- chensis SCHLAGINTWEIT & LOBITZER, Dissocladella? pyriformis SCHLAGINTWEIT and Neomeris mokragoren- sis RADOIČIĆ & SCHLAGINTWEIT, and miliolid fora- minifera (Figs. 8C–D). Stratigraphy: Middle Turonian (based on calcareous nan- nofossils). Randobach near Russbach at Pass Gschütt (locality 5 in Fig. 1). The Randobach river is located about 5 km west of the village of Gosau. Stratigraphy: Santonian (KOLL- MANN & SUMMESBERGER, 1982; KOLLMANN, 1985). From this locality Gosavisiphon gen. nov. was reported by SCHLAGINTWEIT & EBLI (1998: see Fig. 2 for exact lo- cation). Microfacies and associations: Brownish marly lime- stones with the calcareous algae: Gosavisiphon gen. nov., Oroseina pletzachensis SCHLAGINTWEIT & EBLI, Ne- omeris mokragorensis RADOICIC & SCHLAGINTWEIT, Dissocladella? pyriformis SCHLAGINTWEIT, Terquemel la? n. sp., and benthic foraminifera Nummofallotia cretacea (SCHLUMBERGER) and Vidalina hispanica SCHLUM- BERGER. Stratigraphy: Upper Santonian. Hofergraben, Gosau (locality 5 in Fig. 1). This local- ity is situated approximately 1 km southeast of Gosau, Up- per Austria (ÖK 1: 50.000, no. 95 St. Wolfgang) (see Fig. 1C). The material described comes from two small southern tributaries at an altitude of 900 m above sea-level (see Fig. 1 in SCHLAGINTWEIT 2004, for exact location). Gosavi- siphon gen. nov. was already described and illustrated by SCHLAGINTWEIT & LOBITZER (2003b) from this local- ity. The so-called Hofergraben marls (Hofergraben Member of SANDERS & BARON-SZABO 2007) belong to the Hoch moos Formation (see Figs. 1B–C). These marls are well-known for their coral fauna, such as the solitary Cun- nolites (SANDERS & BARON-SZABO, 2007). Microfacies and associations: Gosavisiphon gen. nov. was identifi ed in two different types of siliciclastic-carbonate beds. One is represented by well-sorted arenites with numer- ous specimens with either chaotic distribution or parallel ar- rangement; other biotic elements are scarce (rare benthic foraminifera, shell debris) (see SCHLAGINTWEIT & LO- BITZER 2003a) (Fig. 9A). The other type shows low grade sorting with different extraclasts and numerous algal remains including Trinocladus tripolitanus PIA, Neomeris mokrago- rensis RADOIČIĆ & SCHLAGINTWEIT, Oroseina pletza- chensis SCHLAGINTWEIT & EBLI and Jodotella koradae (DIENI, MASSARI & RADOIČIĆ) (see SCHLAGINTWEIT, 2004) (Fig. 11H). Stratigraphy: Upper Santonian (see Fig. 2 in SANDERS & BARON-SZABO, 2007). Weißwasser-Unterlaussa (locality 6 in Fig. 1). The Weißwasser section near Unterlaussa, Lower Austria (Topo- graphic map of Austria, ÖK 69, Großraming), was studied and illustrated by RUTTNER & WOLETZ (1955), followed by FAUPL et al. (1987) and SANDERS & PONS (1999, Fig. 17). Additional data about the microfauna from this locality were provided by SCHLAGINTWEIT (1992) and SCHLAG- INTWEIT & SANDERS (2008). Outcrops from which sam- ples were taken, are located along the forest road to the Bla- Alm (see SCHLAGINTWEIT 1992, Fig. 4). Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 31 Stratigraphy: Gosavisiphon gen. nov. occurs in a series below rudist limestones (the so-called Liegend-Serie of RUTTNER & WOLETZ, 1955) that have been dated bios- tratigraphically as Middle Coniacian (e.g. WAGREICH, 1990) and on the basis of strontium isotope stratigraphy (STEU- BER, 2001). Therefore, the material with Gosavisiphon gen. nov. may be Early Coniacian or Late Turonian. Microfacies and associations: Marly limestones with cu- neolinids, miliolids (Vidalina hispanica SCHLUMBERGER). Noth-Klamm, Gams (locality 7 in Fig. 1). The Noth- Klamm profi le is located on ÖK 101 Hiefl au, Styria; outcrops are located on the orographic left side of the beginning of the Noth-Klamm (KOLLMANN 1963, 1965; SANDERS & PONS, 1999, Fig. 14). A composite log of the succession of the Gosau Group of the Gams area was presented recently by SUMMES- BERGER et al. (2009) and WAGREICH et al. (2009). Microfacies and associations: The samples with Gos- avisiphon gen. nov. come from a small interval (less than 1 m thickness), of marly limestones between two hippuritid biostromes (Hippurites resectus DEFRANCE). Brownish siliciclastic-infl uenced pack- to fl oatstones with stromatopo- roids (?Cladocoropsis), rudist debris, benthic foraminifera such as Vidalina hispanica SCHLUMBERGER, Quinque- loculina sp., and cuneolinids (Fig. 8B). Calcareous algae are represented by abundant Gosavisiphon gen. nov. and some scattered thalli of Marinella lugeoni PFENDER. Stratigraphy: Upper Turonian, with Barroisiceras haber- fellneri (HAUER), compare SUMMESBERGER & KEN- NEDY, 1996) (Noth Formation of SIEGL-FARKAS & WAG REICH, 1997). 2.2. Branderfl eck Formation Urschlauer Achen, Ruhpolding. At Urschlauer Aachen in the Bavarian Alps, (topographic map of Germany no. 8241), an olistostrome is exposed, intercalated in Lower to Middle Turonian marls, (dated by nannoconids and planktonic fora- minifera, SCHLAGINTWEIT & WEIDICH, 1991; SCHLA- GINTWEIT, 1992). Calcareous green algae occur in differ- ent olistolites of Middle/Late Cenomanian and/or Lower Turonian age with Heteroporella lepina PRATURLON, Per- mocalculus sp., Harlanjohnsonella annulata ELLIOTT, Sal- pingoporella turgida RADOICIC, Trinocladus tripolitanus RAINERI. Stratigraphy: The olistolites in which strongly recrystal- lized specimens of Gosavisiphon nov. gen. were observed are most probably of Middle/Late Cenomanian age. 3. SYSTEMATICS The morphological features of Gosavisiphon gen. nov. pau- cimedullaris (SCHLAGINTWEIT & EBLI) comb. nov., ori- ginally described as a species of the genus Halimeda, neces- sitates a short introduction to the taxonomy of the siphonal calcareous green algae Halimedaceae and Udoteaceae, to- gether with short overviews on "Fossil versus Recent Hal- imeda species" and "Phylloid algae", prior to the systematic description of the alga. 3.1. Taxonomic overview of fossil siphonal green algae of the Udoteaceae and Halimedaceae families. The classifi cation of fossil 'halimediform udoteaceans', (FLÜ- GEL, 2004, p. 423) (Codiaceae versus Udoteaceae versus Halimedaceae) is a matter of long lasting discussions (e.g. MU, 1991; DRAGASTAN et al., 1997). For a long time the Udoteaceae was the accepted family where Halimeda and allied taxa have been included. These were placed into the (segmented) Codiaceae (e.g. STEINMANN, 1899; ELLI- OTT, 1965). The fossil Udoteaceae were treated systemati- cally by BASSOULLET et al. (1983), including not only the Mesozoic and Cenozoic genera Halimeda LAMOUROUX, Boueina TOULA, Arabicodium ELLIOTT, Nipponophycus YABE & TOYAMA and Lekhamptonella ELLIOTT, but also Palaeozoic taxa, for example Tauridium GUVENC, Lancic- ula MASLOV, Dimorphosiphon HOEG (see BOYD, 2007) and some others (e.g. ROUX, 1985; HUBMANN, 1990, 1994; HUBMANN & FENNINGER, 1997; HUBMANN, 2000). The work of BASSOULLET et al. (1983) included only erect segmented taxa, and phylloid algae ascribed to the Udo tea- ceae (see following separate chapter) were excluded. Mod- ern algal taxonomy lists the Udoteaceae AGARDH and Hal- imedaceae LINK as two separate families within the order Bryopsidales (former Siphonales), and Halimeda (with 44 species) as the only genus of the Halimedaceae (e.g. algae- Base of GUIRY & GUIRY, 2009). It is worth mentioning that DRAGASTAN et al. (1997, p. 77), included two genera in the family Halimedaceae, Halimeda and Tydemania. For the Udoteacae, on the other hand, the algaeBase mentions eighteen genera, some of which, however, are considered by some workers to be excluded from this family (e.g. CURTIS et al., 2008). In order to avoid a misleading mixing of fossil and modern taxa, this compilation should exclude Pseudo- penicillus DRAGASTAN et al., 1997 (Late Triassic of Gre- ece), as it represents an exclusively fossil taxon (DRAGAS- TAN et al., 1997). The remaining seventeen extant genera represent a rather heterogeneous group, concerning the highly diverse thallus architecture and the fact that both calcifying and non-calcifying forms are enclosed. The bauplan is gen- erally tripartite with an anchoring holdfast, a stipe and the blade (e.g. Fig. 3A,B). In some udoteacean algae such as Udotea or Avrainvillea, the length of the bulbous holdfast can equal or even exceed the algal parts that project above the sediment surface (e.g. LITTLER & LITTLER, 1990, 1992). As for representatives of the Halimeda, udoteacean taxa may also show different constructional types of the an- choring holdfast as adaptations to different substrates (e.g. LITTLER & LITTLER, 1990: genus Udotea; LITTLER & LITTLER, 1992: genus Avrainvillea). Previously, fi ve taxa were assigned to the Halimedaceae (HILLIS-COLINVAUX, 1984; HILLIS, 1991): Halimeda LAMOROUX, Penicillus LAMARCK, Rhipocephalus KÜTZ ING, Tydemania WEBER-VAN BOSSE and Udotea LAMOUROUX. The latter four have now been included in the Udoteaceae (e.g. GUIRY & GUIRY, 2009). Extant gen- era of the Udoteaceae that calcify are Penicillus LAMARCK, Rhipidosiphon MONTAGNE, Rhipocephalus KÜTZING, Geologia Croatica 63/1Geologia Croatica 32 Tydemania WEBER-VAN BOSSE and Udotea LAMOUR- OUX (Figs. 3A,B). Calcifi cation differs between genera (and species), varying from light to medium, but in any case to a lesser extent than in the Halimeda (e.g. BÖHM, 1973; LIE- BEZEIT & DAWSON, 1982; RIES, 2006). For example, within the genus Udotea LAMOUROUX we fi nd both cal- cifi ed (e.g. Udotea fl abellum, see Fig. 3B), and non-calcifi ed species (e.g. Udotea petiolata, see COLOMBO, 1978). As a consequence of this, many present day Udoteaceae have no fossil record, because of the lack of thallus calcifi cation. Concerning the possibilities of principal descents in the fossil record, the calcifying taxa of the Udoteaceae are worth noting. According to VERBRUGGEN et al. (2009, Fig. 4), Udotea should have its fi rst appearance in the Late Jurassic, Rhipidosiphon in the Late Cretaceous and Rhipocephalus during the Cenozoic. These assumptions, however, have so far not been validated by the fossil record. KÜHNEL (1932) described Udotea adnetensis from the Late Triassic (Rhae- tian), commented on its relationship with the genus Mitch- eldeania JOHNSON & PIA (1942) assigned it to the so- called "porostromate algae". Diagnosis of both the Halimedaceae and Udoteaceae families are not common in the palaeontological literature. Taking a closer look at the examples provided by DRA- GASTAN et al. (1997, 2002) (see Tab. 2), the non-segmented and non-ramifi ed character of the Udoteaceae is worth men- tioning. The eponymous genus Udotea shows different shap es, e.g. disk-like, fl attened or cyathiform (cup-shaped, Udotea cyathiformis), or blade morphology from uncorticated to densely corticated (see monograph of LITTLER & LIT- TLER, 1990 for details; COLOMBO, 1978). For example, Udotea cyathiformis (Fig. 3A) posseses a blade without cor- ticated fi laments, and Udotea fl abellatum (Fig. 3B) a blade corticated by branched fi laments (e.g. LITTLER & LIT- TLER, 1990). Another morphological type of Udoteaceae is represented by Rhipocephalus commonly known as the pi- necone alga with an oval thallus, composed of concentric, tightly packed layered blades. The systematics of the fossil Halimedaceae has changed considerably during recent decades. According to DRA- GASTAN et al. (2002, p. 15), this family should include the following fi ve genera: Halimeda LAMOUROUX, Juraella BERNIER, Hydracara DRAGASTAN, KUBE & RICH- TER, Hikorocodium ENDO and Collarecodium BRAND- NER & RESCH. From these, only Halimeda has extant rep- resentatives. Hikorocodium has been shown to represent an inozoid sponge (SENOWBARI-DARYAN & RIGBY, 2007), and Hydracara has only recently been transfered to the fam- ily Praecodiaceae DRAGASTAN (DRAGASTAN, 2008). Recently, some more new genera from the Late Triassic were Fi gu re 3: Examples of extant (A–B) and Palaeozoic (C–D) Udoteaceae. A) Udotea cyathiformis DECAISNE, Bahamas, blade without corticated fi laments (= ecorticate). B) Udotea fl abellum (ELLIS & SOLANDER), Florida (from AGAS- SIZ, 1880, fi gured as U. fl abellata LAMOUROUX), blade corticated by branch- ed fi laments. C) Ivanovia tebagaensis TORRES, Permian (redrawn from TORRES, 1995). D) Calcipatera cottonwoodensis TORRES, WEST & SAVIN, Low- er Permian of Kansas (slightly modifi ed from TORRES et al., 1992). Scale bars 2 cm for A, 1 mm for B, 2 mm for D. A B C D Table 2: Diagnostic characterization of the two families Udoteaceae and Halimedaceae (from DRAGASTAN et al., 1997, 2002). Note that the features refer to fossil taxa whereas in extant forms much more data (e.g. molecular data, morphology of the non-calcifi ed parts) are available for characterization. The stipe and the holdfast of the Udoteaceae, that together with the blade are the three basic thallus components are not reported from fossil taxa. Order Bryopsidales Suborder Halimedinae Halimedaceae Calcareous thallus, segmented, ramifi ed, formed by cylindrical, oval, fl abelliform or cuneate in shape, crossed by medullar and cortical siphons having diff erent arrangements from species to species DRAGASTAN et al., 1997 Thalli segments with multishapes or morphae from cylindrical until disk-like fl attened crossed by multiaxial medullar siphons and cortex with many utricle series from 2 up to 7 DRAGASTAN et al., 2002 Udoteaceae Calcareous thallus (= blade), fl abelliform, nodular, hemispherical, more or less fl attened, without segments. The genera have ecorticate, partial corticate and corticate thalli, the last ones sometimes without medullar and cortical zones DRAGASTAN et al., 1997 Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 33 assigned to the Halimedaceae (SENOWBARI-DARYAN & ZAMPARELLI, 2005), altogether showing rather poor pres- ervation of their internal structures, (medullary and cortical siphons) and not facilitating detailed comparisons with mod- ern halimedaceans (Tab. 3). Except for Boueina, that is also known from the Late Triassic (e.g. FLÜGEL, 1975; SE- NOWBARI-DARYAN & HAMADANI, 1999), none of the Triassic halimedacean taxa, predominantely reef-dwelling species, survived the reef crisis at the end of the Triassic. At present, Halimeda is considered the only extant genus of the family Halimedaceae LINK, but there is still no consensus about the fossil members not only of the family Halime- daceae, but also the Udoteaceae. 3.2. Fossil versus Recent Halimeda species In former times, palaeontologists dealing with Halimeda (and allied taxa) were exclusively referring to related fossil taxa, and biologists to extant species when discussing their material. In the last decade researchers of both fi elds tried to combine and synthesize the existing data of fossil and recent taxa, with some controversial results (e.g. DRAGASTAN et al., 2002, 2003; DRAGASTAN & HERBIG, 2007; KOO- ISTRA et al., 2002; VERBRUGGEN & KOOISTRA, 2004; VERBRUGGEN, 2005; VERBRUGGEN et al., 2005, 2009). The complex suprageneric taxonomic history of Halimeda has been briefl y summarized in the previous chapter. As pa- laeontologists can only deal with the dispersed calcifi ed parts of the alga, the understanding of the morphological bauplan of the green alga Halimeda is vital before going into detail. Recent representatives of Halimeda currently number 34 species (e.g. VERBRUGGEN & KOOISTRA, 2004) and are composed of fl attened calcifi ed segments, interconnected by non-calcifi ed nodes that haven’t yet been reported from fos- sil taxa (e.g. HILLIS-COLINVAUX, 1980) (Figs. 4A,B). Towards the bottom, the thallus of Halimeda is attached by Fi gu re 4: A–B Thallus morphology of the genus Halimeda LAMOUROUX (from VICKERS & SHAW, 1908). C–H Segment morphology of Recent (C) and Pleistocene (D–H) Halimeda species (from DRAGASTAN et al., 2002, 2003). I–J Transverse sections of Boueina (I) and Halimeda (J). A) Halimeda incrassata (ELLIS). B) Halimeda opuntia (LINNAEUS). C) deeply trilobed segment of Halimeda opuntia f. trilobata (DECAISNE). D) ovate segment of Halimeda copiosa GOREAU & GRAHAM. E) reniform (kidney-shaped) segment of Halimeda gracilis HARVEY ex AGARDH. F) rounded disc-like segment of Halimeda tuna (ELLIS & SOLANDER). G) elliptical-discoid segment of Halimeda copiosa GOREAU & GRAHAM. H) triangular rounded segment of Halimeda tuna (ELLIS & SOLANDER). I) Transverse section of Boueina hochstetteri TOULA, Aptian of Serbia; intersiphonal spaces in white, representing sparry calcite (from STEIN- MANN, 1899). J) Transverse section of Halimeda cylindracea DECAISNE, Recent, Australia; intersiphonal spaces in black (from STEINMANN, 1899). K) Sche- matic drawing of a longitudinal section of Halimeda (without scale), modifi ed after HILLIS-COLINVAUX, 1980). A F B G K H C D E J I Geologia Croatica 63/1Geologia Croatica 34 means of a holdfast, consisting of branching rhizoids (HILL- IS-COLINVAUX, 1980; VERBRUGGEN & KOOISTRA, 2004). Depending on the sediment-type, (hard, sandy, rub- ble), holdfasts may be felt-like (rock grower), bulbous (sand grower) or composed of only a few branched and loose rhiz- oids at intervals along the plant (sprawler) (VERBRUG- GEN, 2005, Figs. 7–9). The construction of the holdfast can be considered a habitat strategy (e.g. substrate, water energy) (e.g. HILLIS-COLINVAUX, 1977). Fossil holdfasts of Hal- imeda have not been reported up to now. Based on the different pattern of nodal medullary fi la- ment arrangement, fi ve sections (= groups of species that refl ect fundamental phylogenetic divergences), are currently recognized (HILLIS-COLINVAUX, 1980; VERBRUGGEN & KOOISTRA, 2004), an approach impossible to conduct with fossil material. The calcifi ed segments are highly vari- able in shape (often also within one and the same species), elliptical-discoid, lobed, ovate, rounded, triangular, irregu- larly quadrangular, reniform to ear-shaped, kidney-shaped, cuneate (e.g. DRAGASTAN et al., 2003; VERBRUGGEN, 2005, Fig. 10–18) (see Figs. 4C,H). Besides this two-dimen- sional segment typology, Halimeda segments may be dis- tinctly undulated, keeled or ribbed (e.g. VERBRUGGEN, 2005, Figs. 19–21). In extant Halimeda, new segments (or daughter segments) originate terminally at the tips of the older (or mother) segments either in direct continuation of the axis or beside the axis, for instance in cases when two new segments arise, as visible in the specimen of Halimeda opuntia shown in Figure 4B. This construction is often term ed 'serial-segmented' (details in ELLIOTT, 1982). It is notewor- thy that there is a terminological dissent between botanists and palaeontologists concerning the numeration of the cor- tical siphons/utricles. For extant species, the numeration of the utrical series (or orders) starts from the segment surface inwards; for example, the outermost ones are termed primary utricles, and so on (e.g. HILLIS-COLINVAUX, 1980; VER- BRUGGEN, 2005). By describing fossil representatives, the numeration used by the palaeontologists is simply the other way around, with the fi rst cortical siphons arising from the meduallary siphons assigned to as primary or of fi rst order. In the case of the Dasycladales, both the phycologists (BERGER & KAEVER, 1992) and palaeontologists (e.g. BASSOUL- LET et al., 1975; DE CASTRO, 1997) use the same numer- ation for different orders of laterals. If we bear in mind that the reduced nodal region between two subsequent segments is composed only of medullary siphons and the cortical si- phons arise from the latter in the segments, the botanical method of numeration is somehow misleading, bearing in mind that the primary utricles are also called peripheral utri- cles. Here, the palaeontological nomenclature is followed. There are contradicting views among phycologists and palaeontologists concerning the fi rst appearance of Halimeda as a genus, or more precisely its different phylogenetic line- ages. In recent times the so-called molecular clock method has been applied to decipher the phylogeny of Halimeda (VERBRUGGEN et al., 2009). This method needs fi xed cal- ibration points "where a clade in the tree has a derived char- acter that is unique to that clade and that can be traced in the fossil record. In this case one can infer that (a) the clade must have evolved on the branch of the tree leading to the the base of the clade and (b) that the clade must have evolved prior to its fi rst occurrence in the fossil record" (MEDLIN, 2007, p. 31). According to DRAGASTAN et al. (2002) and VERBRUGGEN et al. (2009), Halimeda should have its fi rst appearance in the Permian, based on Halimeda soltanensis PONCET selected as the only fossil 'Halimeda' and used as a calibration point for the phylogenetic calculations and con- siderations, thus not achieving the 'ideal scenario'...."with multiple fossil calibration points" (VERBRUGGEN & THE- RIOT, 2008, p. 245). The attribution of this species to the genus Halimeda, however, is treated differently among pal- aeontologists. Whereas DRAGASTAN et al. (2002) consider it a true Halimeda, VACHARD et al. (2001, p. 382) treat it as a phylloid alga comparable to Anchicodium JOHNSON (Fig. 5; see section on phylloid algae). This view is followed here, as H.? soltanensis is obviously missing a medullar zone and only has two bilateral cortices. Moreover, the morphol- ogy of the cortical siphons with their peculiar multiple swell- Table 3: Extant and fossil genus inventory of the family Halimedaceae, modifi ed after DRAGASTAN et al. (2002) with supplementary data of SENOWBARI-DARYAN & ZAMPARELLI (2005). Hikorocodium included in the family Halimedaceae by DRAGASTAN et al. (2002) has been shown to represent an inozoid sponge (SENOWBARI-DARYAN & RIGBY, 2007, for de- tails) and is therefore excluded from the compilation. DRAGASTAN et al. (1997) also included the genus Tydemania Weber-van Bosse as an extant genus of the Halimedaceae; more workers, however, included it within the family Udoteaceae (e.g. SILVA et al., 1996). This compilation includes 10 genera (7 when accepting the synonymy of Arabicodium, Boueina and Nip- ponophycus with Halimeda as suggested by DRAGASTAN et al., 2002). Note that the Late Palaeozoic Eugonophyllum KONISHI & WRAY was placed in the family Halimedaceae by FORSYTHE et al. (2002), most probably mean- ing the Udoteaceae as accepted here. Family Halimedaceae Link Extant Fossil Halimeda Lamouroux, 1812 Alpinocodium Senowbari-Daryan & Zamparelli, 2005 (A. fl uegeli Senowbari. & Zamp., Late Triassic) Arabicodium Elliot, 1957 (A. aegagrapiloides Elliot, Lower Cretaceous) Brandneria Senowbari-Daryan & Zamparelli, 2005 (B. dolomitica Senowbari-Daryan et al., Middle Triassic) Boueina Toula, 1884 (B. hochstetteri Toula, Lower Cretaceous) Calabricodium Senowbari-Daryan & Zamparelli, 2005 (C. irregularum Senowbari. & Zamp., Late Triassic) Collarecodium Brandner & Resch, 1980 (B. oenipontanum Brandner & Resch, Middle Triassic) Egericodium Flügel et al., 1992 (E. hungaricum Flügel et al., Late Triassic) Juraella Bernier, 1984 (J. bifurcata Bernier, Late Jurassic) Madonicodium Senowbari-Daryan & Zamparelli, 2005 (M. noricum Senowbari. & Zamp., Late Jurassic) Nipponophycus Yabe & Toyama, 1928 (N. ramosus Yabe & Toyama, Late Jurassic) Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 35 ings is different from the infl ated or cylindrical utricle struc- ture of Halimeda (e.g. VERBRUGGEN, 2005). Last but not least, a cylindrical morphology has been assumed by PON- CET (1989), but not evidenced by illustrations, another char- acteristic pointing to the phylloid Anchicodium (see section on phylloid algae, this work). From the fi ve lineages of Halimeda resulting mainly from gene sequencing and differences in the structure of the medullary siphons within the nodal region (e.g. HILLIS et al., 1998; KOOISTRA et al., 2002), the longest stock is re- ferred to Halimeda discoidea by VERBRUGGEN et al. (2009, Fig. 4). This should date back to the Late Jurassic, or Hali- meda cylindracea by DRAGASTAN et al. (2002) to the Late Triassic. Some of these obvious controversies are due to dif- ferent interpretations of segment morphology in fossil taxa and different views concerning the group Arabicodium-Bou- eina-Halimeda with various stratigraphic ranges. It should be noted that up to now, there has been no description or il- lustration of a Triassic to Upper Cretaceous Halimeda spe- cies having fl attened, e.g. discoidal segments (e.g. Fig. 4G). According to DRAGASTAN & HERBIG (2007, p. 8), such shapes should occur in latest Cretaceous times with Hali- meda? johnsoni (Late Cretaceous–Paleogene of India, PAL 1971), considered a synonym of Halimeda opuntia (LIN- NAEUS) (Miocene–Pliocene, Fig. 4B). This possible syn- onymy has already been remarked by DRAGASTAN et al. (2002), following the description of PAL (1971) that the former should be characterized by leaf-like segments. The only fi guration of Halimeda? johnsoni provided by PAL (1971), however, shows a longitudinal section of a cylindri- cal specimen being in accordance with Late Cretaceous sec- tions of the NCA and the Internal Dinarides (Figs. 6A,B). Another Late Cretaceous species with cylindrical segments is Halimeda elliotti described by CONARD & RIOULT (1977), together with the described species of the genera Arabico- dium ELLIOTT and Boueina TOULA (e.g. BASSOULLET et al., 1983, Tab. 3). The works of DRAGASTAN et al. (2002, 2003), a co- production of palaeontologists and phycologists, provided another grouping into three phyletic lines, 'founded on the segment morphology' as the only criterion. The one with the greatest impact on fossil taxa is the proposed 'fi rst phyletic line' of Halimeda cylindracea. With the synonymization of 21 Mesozoic and Cenozoic taxa, including all Late Triassic to Paleocene species of Boueina TOULA and most of Ara- bicodium ELLIOTT, the origin of modern Halimeda should date back into the Late Triassic. Boueina hochstetteri was thoroughly investigated using topotype material by STEIN- MANN (1899). He stressed a remarkable similarity to Halimeda. As one of the main differences STEINMANN mentions that the cortical siphons of Halimeda are swollen at the branching points and that the subsequent higher order siphons are mostly strongly constricted at their bases, fea- tures missing in Boueina (Fig. 4I). Curiously, the latter fea- ture was stressed by CONARD & RIOULT (1977) as one outstanding feature of Halimeda elliotti from the Turonian of France. The fact that the Turonian Halimeda elliotti in turn is put in synonymy with the extant Halimeda cylindra- cea by DRAGASTAN et al. (2002), closes the circle again, leaving ample space for interpretations. The general aspect of the cortical zone of H. cylindracea, composed of three to fi ve layers of utricles (HILLIS-COLINVAUX, 1980), is a more general feature shared with many other species. The synonymization of the genera Boueina TOULA and Arabi- codium ELLIOTT with Halimeda LAMOUROUX (as hav- ing priority, see Tab. 3) is something that can be seriously discussed. However, the assumption that both type-species (Boueina hochstetteri, Arabicodium aegagrapiloides), with their totally different aspects of medullary and cortical zones, represent the same species H. cylindracea, seems to be too radical and needs further refi ned investigations. The more so, as Halimeda cylindracea does not possess real cylindri- cal segments with typical circular transverse sections. In DRAGASTAN et al. (2002, Figs. 3A,B), a fi guration of HILLIS-COLINVAUX (1980) is shown with a thallus of Halimeda cylindracea whose segments were sectioned at various levels (basal, middle, top). From juvenile to adult stages, the segments become more compressed, but none shows a circular transverse section typical of the Late Trias- sic to Cretaceous group of halimedacean-like algae (Hali- meda, Boueina, Arabicodium). Some transverse sections of H. cylindracea tend to be oval (Fig. 4J), but typical com- pressed sections as illustrated by DRAGASTAN et al. (2002) were not reported, for instance, from the well-known fossil Boueina hochstetteri (Fig. 4I). This, however, should be ex- pected in the typical facies with abundant dispersed seg- A B C Figure 5: A–B Anchicodium iranicum SENOWBARI-DARYAN & RASHIDI, in press, from the Permian of Iran, note lateral protuberance/swelling (arrow) in (A), and dimorphic cortices in (B) (= inner and outer cortex sensu TORRES, 2003, Fig. 4). C) Anchicodium sp. from the Permian of South-China (see BU- CUR et al., 2009). The lateral formation of a new plate with reduced width near the bifurcation area and the occurrence of lateral protuberances are comparable to the Late Cretaceous Gosavisiphon (details in the text). Geologia Croatica 63/1Geologia Croatica 36 ments. Hence, the assumption as far back as the cylindrically shaped species H. cylindracea can be traced, is not only highly controversial but also very speculative and therefore is not accepted here. All taxa with cylindrical segments (in- dependently of their generic position, e.g. Boueina, Arabi- codium, some fossil 'Halimeda' species) can not be compared purely morphologically with extant Halimeda, and therefore can not be used for tracing its phylogenetic origin. As the segments and some internal features are the only available criteria for comparison of fossil with extant species, present knowledge (or interpretation) has not resulted in a fi - nal solution. The fi rst fossil Halimeda species that shows seg- ments that can be morphologically directly compared with modern species (see Fig. 4) is from the Early Tertiary with Halimeda eocaenica MORELLET & MORELLET, a species close to the recent Halimeda opuntia (LIN NA EUS) (see BASSOULLET et al., 1983, p. 490). Although nothing is known about the internal structure of Halimeda eocaenica (only known as isolated segments), it was determined as syn- onymous with Halimeda opuntia by DRAGASTAN et al. (2002) and DRAGASTAN & HERBIG (2007). H. eocaenica has fl attened, shallowly lobed segments (see MORELLET & MORELLET, 1940), a morphology previously unknown from Cretaceous halimedacean-like algae with cylindrical segments (genera Boueina, Arabicodium). Halimeda sp. de- scribed here from the Late Turonian Lower Gosau Subgroup of the NCA can morphologically be compared with H. eo- caenica in also having disc-like fl attened segments; a more closer comparison or a transfer of the Turonian form to the Eocene taxa is not possible as nothing is known about the internal structure of the latter. This is also the reason why a new species with a segment morphology so far unknown Figure 6: A–F Halimeda? aff . johnsoni PAL from the Upper Turonian-Coniacian Lower Gosau Subgroup of the Krumbachalm-Nachbergalm area (A, C–F) and the Santonian of the Inner Dinarides, Serbia (B). A) Longitudinal section; sample 20995-3. B) Longitudinal section; sample RR 2273. C) Slightly oblique longitudinal section; sample 1803. D–E) Transverse sections slightly oblique; samples 1803 and 151194/1. F) Oblique section, note comparable large medullary and distinctly smaller cortical siphons; sample 1803. Scale bars 0.5 mm for A–C, E–F; 0.4 mm for D. A B C D E F Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 37 from Cretaceous representatives of Halimeda was not intro- duced. As a further consequence, the origination of Halimeda discoidea during the Late Jurassic as supposed by VER- BRUGGEN et al. (2009), is not substantiated by fossil re- cords; fossil Halimeda showing disc-like fl attened segments are so far not known prior to the Middle Turonian (this study). This age of ~ 92 to 93 Ma (see GRADSTEIN et al., 2004) can be used as a calibration point for a clade of Halimeda with ovate fl attened segments, such as Halimeda opuntia. According to the molecular clock approach, this morpho- logical characteristic of modern Halimeda must have evolved prior to its first fossil appearance, probably around the Lower/Upper Cretaceous boundary. Such an interpretation would be in accordance with an assumption already made by ELLIOTT (1965) that Halimeda sensu stricto evolved in the Upper Cretaceous. For the molecular node age with the division of Halimeda opuntia and Halimeda gracilis VER- BRUGGEN et al. (2009) calculated at 97 Ma, this suggests somewhere in the Cenomanian. Bearing in mind that fossil calibration data are minimum ages for the corresponding lin- eages, "because newly evolved character.........do not usually fossilize until they become relatively common" (VERBRUG- GEN and THERIOT, 2008, p. 245), the observed age for Tu- ronian Halimeda sp. with discoidal-fl attened segments seems to fi t well with the molecular age. With respect to the incomplete original descriptions and illustrations of the Late Cretaceous 'Halimeda' paucimed- ullaris and some Early Cenozoic species of MORELLET & MORELLET (1922), KOOISTRA et al. (2002, p. 122) state that these "show similarity to extant groups of species...(of Halimeda)...suggesting that the extant diversity consists of living fossils". In conclusion, these resemblances, however, are interpreted by KOOISTRA et al. (2002) as having re- sulted from iterative convergence therefore representing 'look-alikes'. A completely different view was advanced by HILLIS (1999, p. 186), another expert in modern halime- dacean algae, suggesting that "extant species have appeared relatively recently". Although the present state of knowledge on fossil versus extant Halimeda species has advanced con- siderably, the topic is still a challenge for both phycologists and palaeontologists requiring further high quality, combined research for a thorough interpretation of the fossil record as a basic prerequisite when combined analysis of extant and extinct species should be conducted. 3.3. Phylloid Algae The non-systematic, general term phylloid algae was intro- duced by PRAY & WRAY (1963) for a group of predomin- antely aragonitic algae, with poorly preserved internal fea- tures, that characterized Late Palaeozoic, (mainly Middle Carboniferous to Early Permian) reefal platform margins. They were ascribed mostly to green algae, but some also to red algae (e.g. PRAY & WRAY, 1963; KONISHI & WRAY, 1967; TOOMEY, 1976; FLÜGEL & FLÜGEL-KAHLER, 1980; WAHLMANN, 2002; GONG et al., 2007a, b). Phyl- loid taxa include for instance Ivanovia KHVOROVA, 1946 (Fig. 3C), Anchicodium JOHNSON, 1946, Archaeolithophyl- lum JOHNSON, 1956, Calcifolium MASLOV, 1956, Eu- gonophyllum KONISHI & WRAY, 1961, Calcipatera TOR- RES, WEST & SAWIN, 1992, Kansaphyllum BAARS, 1992, or Kasimophyllum MAMET & VILA, 2004. Their global dominant role and success could have been favoured by the seawater chemistry, particularly the Mg/Ca ratio, facilitating aragonite precipitation during that time (RIES, 2006). The name 'phylloid algae' comes from the greek word phyllon, meaning leaf. The thallus shape of the phylloid algae is highly variable from simple or undulose plate- or leaf-like ('corn fl ake-shaped'), to cyathiform (simple or folded cup- shaped, Figs. 3C–D) (e.g. TORRES, 1995, 2003; FORSY- THE et al., 2002; SAWIN & WEST, 2005). Amongst the forms with cup-shaped thalli, GONG et al. (2007a, b) further differentiated between single cup-shaped, cabbage-shaped and clustering cup-shaped forms. Some phylloid algae may show a structure of supporting plates similar to a house of cards (e.g. Fig. 9A in WAHLMAN, 2002). JOHNSON (1946) and TORRES & BAARS (1992) interpret the morphology of Anchicodium (see Fig. 5) not as being phylloid, but as 'distinctly cylindrical' based on extremely rare, round ed sec- tions. Generally, when Anchicodium should in fact be cylin- drical, circular transverse sections comon, where this alga usually occurs in special types of facies and in great abun- dances. However, this is not the case. Instead, long irregular curved algal thalli can be observed in thin-sections (Fig. 5). The illustrated transverse sections display an oblique radial arrangement of cortical siphons that indicate interpretation as sections cutting lateral 'rounded protuberances' that occur at irregular distances at the external side and that were also included by JOHNSON (1946) in the generic diagnosis (see Fig. 5A). For the phylloid algae, the presence of an anchoring holdfast, comparable to that of the Halimedaceae or Udo- teaceae, was assumed (TORRES et al., 1992), but has so far not been discovered fossilized, perhaps as these were not calcifying. The prostrate Archaeolithophyllaceae CHUVA- SHOV in CHUVASHOV et al. (1987) with internal cellular structure and conceptacles, (red algal affi nities) are com- monly separated from the phylloid algae with green algal characteristics, as the latter may result from the complete sparitization of the former (VACHARD et al., 2001, p. 389, Fig. 15). Other phylloid taxa were included in the family Calcifoliaceae TERMIER, TERMIER & VACHARD (see VACHARD & CÓZAR, 2006). Some of the aforementioned taxa (e.g. Ivanovia) have directly been compared with mod- ern halimedacean algae (e.g. genus Halimeda) (e.g. HAR- BAUGH, 1960; CROWLEY, 1969; KIRKLAND et al., 1993). For example, Eugonophyllum is ascribed to the family Udo- teaceae based on exceptionally well preserved specimens with primary aragonitic skeletons (KIRKLAND et al., 1993). Based on the conclusion of HILLIS-COLINVAUX (1984), that the family name Halimedaceae should have priority over Udoteaceae, the genus Eugonophyllum was placed in the former by FORSYTHE et al. (2002). It should be placed in the Udoteaceae as the present day Halimedaceae are mono- generic (genus Halimeda) (see Tabs. 2–3). For those taxa that were referred to or compared with udoteacean/halimedacean Geologia Croatica 63/1Geologia Croatica 38 algae, the absence of a clearly delimited medullary zone (e.g. Anchicodium, Fig. 5) or its reduced size in some genera is striking; in these cases, a bilateral cortex, sometimes dimor- phic (see Fig. 5B), may arise from the median central part of the alga. In fact, there are superfi cial morphological resem- blances, for instance between Late Palaeozoic cup-shap ed phylloid algae (TORRES, 1995, 1997; TORRES et al., 1992) and extant udoteaceans such as Udotea cyathiformis (see Fig. 3B, D–E). A further cross-link between phylloid and halime- dacean algae is represented by the occurrence of mound structures within both groups (e.g. BRAGA et al., 1996, 'seg- ment reefs'; GONG et al., 2007 a, b; GRAMMER & RIT- TER, 2008). Alternatively, Late Palaeozoic archaeolitho- phyllacean mounds (e.g. genus Archaeolithophyllum), built by an open framework were compared with Holocene deeper water Mesophyllum-dominated boundstones (DAVIES et al., 2004) or with encrusting peyssonneliaceans (JAMES et al., 1988). All examples mentioned clearly demonstrate that the term 'phylloid' does not imply either a particular growth habit, gross morphology or any taxonomic position, and is used as an algal waste-paper basket. Phylloid algae have a discontinuous stratigraphic record with a main acme in the Late Carboniferous-Early, p.p. Late Permian. There is a reappearance in the Late Triassic (Norian) after a gap of about 35 to 40 MA with the single taxon Ivano- via triassica (REID, 1986; TORRES, 2003), one survivor of the mass extinction at the end of the Permian (e.g. PAYNE et al., 2004; JABLONSKI, 2005). Again after a considerable stratigraphic gap of more than 100 MA, another taxon with comparable morphology appears in the Late Cretaceous with Gosavisiphon gen. nov. A phylloid alga was described by DRAGASTAN et al. (1993) from the Bathonian of India; the illustrations, however, do not facilitate further discussion. The obvious absence of this peculiar algal morphology in post- Triassic times and the reasons for its sudden reappearance in the Late Cretaceous are unknown. Perhaps, this morphology arose independently two or more times. 4. Palaeontological Descriptions Division Chlorophyta PASCHER Order Bryopsidales SCHAFFNER Family Halimedaceae LINK Halimeda? aff . johnsoni PAL, 1971 Figs. 6A–F 1971 Halimeda johnsoni, n. sp. – PAL, pl. 1, fi g. 1 Description: Small, cylindrical segments (length: 1.35– 1.40 mm, diameter: 0.2–0.5 mm) with broad-rounded ends, made up of sparry calcite; calcifi cation comprises both med- ullary and cortical zone. Constrictions of the segments are indicated. Medullary siphons large (diameter: 0.024–0.045 mm); cortex consists of fi ner, three (?four) loosely disposed utricle series (diameter: 0.016–0.035 mm), resulting in com- parable large intersiphonal spaces. The ratio of segment width to length is 0.29 to 0.31 (PAL, 1971: 0.240 to 0.375). Comparisons and discussion: In the original descrip- tion, Halimeda? johnsoni was only illustrated by one longi- tudinal section, showing a striking analogy to specimens shown in Figs. 6A–B. As no holotype was indicated in the original paper, this specimen fi gured on plate 1 fi gure 1 by PAL (1971) is designated here as a lectotype. Also the range of the dimensions of the Alpine speci- mens is comparable to those given by PAL (1971) for fi ve segments. There are some minor variances, e.g. the diameter of segments may also be smaller than data from PAL (1971, D: 0.48–0.52 mm). From the specimen illustrated by PAL (1971), a leaf-like morphology was assumed (see DRA- GASTAN et al., 2002; DRAGASTAN & HERBIG, 2007) and the species was synonymized with the extant Halimeda opuntia. The specimens from the Lower Gosau Subgroup, however, clearly show circular cross-sections as expected in cylindrical segments. Halimeda? johnsoni was described from the Maastrichtian-Palaeocene of India, the specimens from the Lower Gosau Subgroup are of Late Turonian-Co- niacian age. Boueina pygmaea (PIA, 1936, Cenomanian- Turonian of Morocco), Arabicodium tibeticum (YU JING, 1976, Paleocene-Early Eocene of Tibet) are comparable to Halimeda? johnsoni as is Halimeda nana (PIA, 1932, Pale- ocene of Morocco) to some lesser extent. The four taxa (in- cluding H.? johnsoni) need systematic reconsideration and re- investigation for the evaluation of possible synonymies. Note that PIA (1936, p. 13) tentatively referred Boueina pygmaea to the genus Boueina rather than Halimeda 'as no bifurcation of the thallus was observed', a non-diagnostic feature, the more so when only dealing with some thin -sections. Last but not least, Halimeda? aff. johnsoni PAL appears in bioclastic packstones with corals, and rudists, and sponges, indicating an open marine paleoenvironment, whereas the other two taxa Halimeda sp. and Gosavisiphon gen. nov. paucimed- ullaris (SCHLAGINTWEIT & EBLI) comb. nov. described from the Lower Gosau Subgroup occur in lagoonal wacke- to packstones with totally different algal fl ora and microfauna. Another observation illustrated here in Fig. 6B is from the Santonian type-locality of Neomeris (Drimella) jerinae in the internal Dinarides of Serbia (see RADOIČIĆ, 1984). Halimeda sp. Fig. 7 Description: Weakly calcifi ed, fl attened, disc-like to broad ovate segment sections (slightly broader than high) of light brownish colour. Typically, only the segment periphery (thick ness: ~ 0.08 to 0.2 mm) with up to three (? four) orders of tiny, cylindrical to cylindroconical cortical siphons is pre- served; the large central part that hosted the medullar zone and the innnermost siphons is represented by a sediment- fi lled cavity. Therefore, nothing can be said about the inter- nal structure. Transverse sections sometimes are bent and display varying thicknesses. For dimensions see Table 4. Comparisons and discussion: At the Pletzachalm lo- cality Halimeda sp. and Gosavisiphon gen. nov. paucimed- ullaris (SCHLAGINTWEIT & EBLI) comb. nov. co-occur. Due to external morphology, degree of calcifi cation and other features, both can easily be distinguished. The ovate segment morphology was previously unknown from the Cretaceous Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 39 (and older) Halimeda species, so these segments could be- long to a new species. A comparable segment morphology is known from Halimeda eocaenica MORELLET & MORE- LLET; the dimensions of the Cretaceous specimens are smaller, but this feature is not diagnostic as variable sizes and also segment forms may occur in different parts of a Halimeda thallus (see Figs. 4A–B). The Eocene taxon is only known from isolated segments; internal structures are un- known. Isolated segments of H. eocaenica were also col- lected by GENOT (1985a, p. 210) but not studied by means of oriented sections, as these were recrystallized affecting both medullary and cortical siphons. Thus, we can not ex- clude but also not validate that the Turonian specimens be- long to Halimeda eocaenica MORELLET & MORELLET. Therefore, synonymization of the fossil Halimeda eocaenica with the Recent Halimeda opuntia by DRAGASTAN & HERBIG (2007, p. 8), on the feature of comparable segment shapes alone, seems premature as the "the cortical system with variously shaped utricle series remains the primary key for identifi cation of fossil material and corresponding extant material" (op. cit., p. 15). ? Family Udoteaceae AGARDH (Remark: refering to SILVA, 1980) Remark: Notwithstanding and obviously unaware of the common knowledge on botanical taxonomy, the Udoteaceae were introduced as a new family name with diagnosis by NIZAMUDDIN (1963) almost 80 years after the establish- Figure 7: A–C Segment sections (outlined in red) and morphology of Halimeda sp., Late Turonian of Pletzachalm. A–B Transverse sections, sample Pletz 7 and sample BSP 5211a-93. C Longitudinal section in the plane of compression, sample Pletz 7. Note the totally decalcifi ed medullary zone also aff ect- ing the innermost cortical utricles in all three specimens. Above right: Schematic segment outline from A; below: Schematic segment outline from C. H = segment height, W = segment width, T = segment thickness. A B C Table 4: Segment dimensions (in mm) of Halimeda sp., Upper Turonian of Pletzachalm (samples 5211a 93 and Pletz 7) and Eisenbach (sample EB 9B). H = segment height, W = segment width, T = segment thickness. W T H sample – 0.64 – 5211a93 – 0.40 – 2.10 0.40 – Pletz 7 2.40 – 1.90 1.05 0.35 – EB-9B Geologia Croatica 63/1Geologia Croatica 40 ment of the family. Gosavisiphon gen. nov. surely belongs to the green alga order Bryopsidales, however, the family rank is uncertain. Refering to fossil udoteaceans as segmented or non-seg- mented algae with an internal unpartitioned siphonal con- struction, Gosavisiphon gen. nov. is for reasons of pragma- tism and taxonomic simplicity also placed in this family. The question of whether it belongs to the Halimedaceae can def- initely be excluded (see Tab. 2). Perhaps, the combination of the external and internal morphology necessitates the es- tablishment of a new family with at present only one genus. Gosavisiphon gen. nov. Origin of the name: The genus name refers to the latinized name of Gosau, named after the village of Gosau, Lower Austria (see Fig. 1C), combined with the siphonous inner structure. Type species: Halimeda paucimedullaris SCHLAGINT- WEIT & EBLI, 1998. Diagnosis: Plurimillimetric to pluricentimetric, irregu- larly curved and twisted, non-segmented and non-branching plates, occasionally with irregularly distributed swellings; distal margins slightly thickened, rounded. Basal part stra- tose, attaching to hard substrates by means of fl at crusts, ocassionally with small rhizoidal outgrowths. Cortication comprises both the basal and erect part. Plates partly fused laterally showing multilateral cortices separated by a thin sparitic line (?extracellular cement). The internal non-septate siphonal construction consists of an often sparitic median line (?reduced medullary zone), from which bilateral corti- ces originate. Cortices with 3–5 layers of utricles mostly di- chotomously, sometimes also trichtomously branched, and set at right angles to slightly oblique to the median plane; internal siphons long, cylindrical to cylindroconical occa- sionally with a moderate terminal swelling, peripheral si- phons rather short. Breakage of thallus preferentially along the median plane leading to the formation of fragments with unilateral cortices. Calcifi cation well developed; siphons fi lled with blocky calcite, intersiphonal spaces of light to dark brownish appearance. Reproductive structures and ex- act three-dimensional thallus architecture unknown. Composition: So far monospecifi c. Comparisons and discussion: The taxon in question was originally described as a species of the genus Halimeda LAMOUROUX by SCHLAGINTWEIT & EBLI (1998), characterized above all by its reduced medullary zone (as refl ected in the species name) and having cylindrical seg- ments. As discussed below, the thallus organization of the gosauian taxon is on the whole completely different from Halimeda. In the original description of Halimeda pauci- medullaris, the segment morphology was erroneously re- ported as being cylindrical because of the supposedly fi nger- shaped sections with parallel outer margins. Moreover, the original description was based on comparable short thallus parts only; the wavy plurimillimetric to pluricentrimetric specimens were only discovered afterwards (SCHLAGINT- WEIT & LOBITZER, 2003). Already DRAGASTAN et al. (2002, p. 16) quoted that the segments of Halimeda pauci- medullaris are not, as erroneously indicated, cylindrical, but fl attened, most probable nearly discoidal. DRAGASTAN et al. (2002, p. 17) claim the species validity "with distinct structure and morphology that cannot be referred to any of the Recent species of the genus" (= Halimeda). Sections of very long (> 2 cm length) and thin (~ 0.4 to 0.5 mm) speci- mens led us to conclude that these are not individual seg- ments and parts of a segmented alga like Halimeda (see Figs. 4A–B). The general shape and their wavy outline in cross sections are not compatible to the segment sizes and mor- phology (including also the ratio length/width) of any known Halimeda, both extant and extinct (Figs. 4C–H), and there are several indications that in Gosavisiphon gen. nov. instead we are dealing with plate-like phylloids (or membranes): (a) The specimen shown on Fig. 10A, represents a sec- tion with a more or less constant thickness (~0.4 to 0.5 mm) over a length of more than 2 centimetres. This specimen is the only one observed in this thin-section and the probability that it is directly cut exactly in the middle of a cylinder along its total length is improbable (compare with the same con- sideration for Anchicodium, in the section on phylloid algae, Fig. 5). This also accounts for the large specimens shown in Figs. 8A and 9D, or very long specimens, or variously bent specimens. If a bent specimen of a small cylinder is cut in random thin-sections, we would fi nd interruptions in the lon- gitudinal section with tapering on both sides of the part that bends away from the cutting plane. (b) In all thin-sections studied, we never observed a rounded/circular transverse section with a central medulla and radially arranged cortical fi laments provided by cylin- drical segments. The sometimes assymetric appearance of the cortices, i.e. different thicknesses on oppsite sides in sec- tions, suggests a phylloid of reduced width comparable to a belt or plate. Thus, in oblique longitudinal sections the median plane is not centreed as would be expected when referring to a cylindrical morphology. Furthermore, several fl attened- ovoid transverse sections recovered, support the inferred mor- phology (Figs. 14K–M). (c) The characteristic debris of Gosavisiphon is com- posed of fragments consisting only of unilateral cortices. This type can be explained by the less well calcifi ed median, facilitating preferential damage/breakage along this plane of the algal phylloids. Apart from this, these fragments are also formed by the lateral formation of new phylloids and their easy disintegration (see Fig. 14, for explanation). (e) The wavy segments can morphologically directly be compared with the so-called phylloid algae. Besides the general morphology being totally different from Halimeda, the internal structure also shows differences. First of all, the often total lack of a central medullary zone is striking, whereas in Halimeda this zone can (differing from one species to the other) make up more than 3/4 of the seg- ment diameter, consisting of multiple longitudinally arranged medullary fi laments. Only in Halimeda cryptica COLIN- VAUX & GRAHAM and Halimeda pygmaea VERBRUG- Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 41 GEN, LITTLER & LITTLER, is the medulla composed of a single fi lament (COLINVAUX & GRAHAM, 1964; VER- BRUGGEN et al., 2007). Finally, Halimeda is anchored in the sediment by means of a rhizoidal holdfast (Fig. 4A); Gos- avisiphon in contrast represents an alga with a fl at prostrate thallus portion with rhizoidal outgrowths fi xed to biogenic hard substrates. Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI, 1998) comb. nov. Figs. 8–12, 14E–F, K–M 1985 Halimeda sp. – HÖFLING, pl. 11, fi gs. 7–9 1993 Halimeda sp. – MOUSSAVIAN, HÖFLING & HERM, pl. 4, fi g. 3 Figure 8: Microfacies with Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI) from the Lower Gosau Subgroup of the Northern Calcareous Alps. A) Left: Mixed siliciclastic-carbonatic tempestitic layers intercalated in the Hofergraben Marls with abundant, chaotic oriented algal plates appearing as dark, brownish curves forming a fl oatstone facies. Locality Hofergraben, east of the village of Gosau; stratigraphy Upper Santonian, sample HG 3D. Right: Same fi guration, specimens of Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI) are coloured in orange. B) Left: Brownish marly limestone (bioclastic packstone to fl oatstone) with one curved specimen. Noth-Klamm, Gosau of Gams, Upper Turonian. Right: same fi gured specimen of Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI) coloured in orange. C) Wacke- to fl oatstone with branching thallus of the dasycladale Thyrsoporella eisenbachensis SCHLAGINTWEIT & LOBITZER (T) and plate of Gosavisi- phon (G). Eisenbach locality; stratigraphy Middle Turonian, sample EB-9B. D) Close-up view of C showing plate of Gosavisiphon. A B C D Geologia Croatica 63/1Geologia Croatica 42 Figure 9: Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI) from the Upper Santonian Hofergraben Marls, mixed siliciclastic-carbonatic tempestite layers (A–D) and the Late Turonian Lower Gosau Subgroup of the Nothklamm, Gams (E–F). A) Four plates in parallel arrangement/orientation, sample HG-3B. B) Specimen showing a sparitic, probably monosiphonal medullary zone from which in a perpendicular manner cortical siphons of several orders originate, sample HG-3B. C) Specimen with extremely reduced to lacking medullary zone; note elongated and distally widening primary siphons (utricles), sample HG-3D. D) Long algal plate with fused plate parallely at longer distance (above) showing a little darker colour. E) Long, slightly undulating algal plate with unilateral cortex; note sparitic central line, sample HG-3D. F) Detailed view from E showing tapering and change of orientation of the cortex. A B C D E F Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 43 1998 Halimeda paucimedullaris n. sp. – SCHLAGINT- WEIT & EBLI, pl. 1, fi gs. 1–3, 6; pl. 2, fi gs. 1–2 2003b Halimeda paucimedullaris SCHLAGINTWEIT & EBLI – SCHLAGINTWEIT & LOBITZER, pl. 1, fi gs. 1–3 2004 Halimeda paucimedullaris SCHLAGINTWEIT & EBLI – SCHLAGINTWEIT, pl. 1, fi g. 3 Diagnosis: See diagnosis of the monotypic genus. Description: The alga is well calcifi ed with sparite fi lled siphons and an intersiphonal part showing a light-brownish, more seldom slightly yellowish appearance. The thallus is differentiated into a basal prostrate portion and an erect part. It was found encrusting biogenic substrates such as metazoan skeletons (e.g. stromatoporoids) or fragments of rudistid shells (Fig. 12). The crustose part (thicknesses mostly from < 0.1 mm to 0.4 mm) directly follows the substrate surface, often for lengths of several millimetres; in this connection, small rhizoidal outgrowths of the crusts may enter existing hollows (observed up to ~ 0.5 mm in depth), such as skeletal pores. Depending on the geometry of the substrate pores, these rhizoidal outgrowths may be straight or strongly bent in order to completely fi ll the former. Smaller shell debris can also become totally encrusted on all sides. These exam- ples were observed without the erect part; it must remain open, whether this is due to breakage or it being a special morphotype lacking an erect part. In many cases, the crusts are diagenetically obliterated appearing as a dark brownish mass with poorly preserved internal features; a central spar- itic line and fi ne cortical siphons, however, are discernible. Within the crusts, the sparitic line, interpreted as a strongly reduced medullary zone (?monosiphonal), can be either at the base just between the substrate and the algae (?acting as cement) or more or less in the central part. In the fi rst case, only a simple monolateral cortex is present with siphons per- pendicular to the substrate and dividing in growth direction. Alternatively, a cortex, developed on both sides (bilateral cortices) is present. Commonly, the algal thallus becomes erect, bending away from the substrate mostly gradually with low inclination. Then another plate may attach that grows in the opposite direction; the length of the attaching plane be- tween the two plates is variable; in any case a thin sparitic crust interpreted as extracellular cement is developed. Often ends or margins of the plates seem to be broken leaving only remnants with unilateral cortices, which together with the fact that the observed plate arrangements seem to be some- how incomplete (missing of whole attaching plates), means that the three-dimensional thallus architecture is unclear. More rarely, individual plates may also bend away from the substrate in a perpendicular manner. The plates (or phylloids, or thallus membrane) maybe more or less straight (at least along longer portions, Fig. 10a) but more often irregularly bent also showing constricted and swollen areas (e.g. Figs. 10G–J). The plates vary in thick- ness from 0.2 mm to 0.68 mm averaging 0.4 mm (n = 30); the greatest observed length is 2.1 centimetres (Fig. 10A). At the Eisenbach locality, very small plates with thicknesses around 0.1 mm were observed, that somehow due to their microfacies, can be interpreted as phenotypic variations (Figs. 8C–D). Anyway, the total biometric ranges can be re- garded as certainly obscured by breakage and diagenetic processes (e.g. compression). Normally, a central sparitic line, that could be interpreted as a monosiphonal medulla, is present. In parts where new plates are attached, this zone moves toward the margin and fi nally forms the outer zone of the one plate and concurrently acts as the base of the at- taching plate where a monosiphonal cortex develops (Figs. 11A–C). In these portions a multilateral (or tri-lateral) cor- tex is present (see Fig. 14 for explanation), meaning a bilat- eral cortex from the attached plate and a monolateral cortex from the fusing plate, being in contuity with the siphonal branching direction, is visible in thin-sections. Remarks on calcifi cation: In the investigated thin-sec- tions, not only Gosavisiphon but also the accompanying da- sycladalean algae namely Neomeris mokragorensis RADOI- ĆIČ & SCHLAGINTWEIT, or in the tempestite layers of the Hofergraben marls also Trinocladus tripolitanus RAINERI and Jodotella koradae (DIENI, MASSARI & RADOIĆIČ) show the same characteristic light brownish appearance (see SCHLAGINTWEIT, 2004, Pl. 1) (Fig. 13). This so-called 'brown calcifi cation'may represent either primary calcite or aragonitic relicts (see discussion in MASSE & BUCUR, 2002, p. 160). Recent dasycladalean algae develop essen- tially aragonitic skeletons (e.g. BERGER & KAEVER, 1992); whereas in fossil species the original crystalline phase and microstructure have been destroyed by diagenetic re- crystallization (e.g. overview in DE CASTRO, 1997, p. 165). Well preserved isolated dasycladalean thalli that have re- tained their original aragonite were reported by GÉNOT (1980, 1985a, b) from the Tertiary of the Paris Basin. Excep- tions with skeletons of radial fi brous (?calcitic) crystals or dark micritic skeletons may also exist (e.g. CONRAD & VAROL, 1990). Hence, for the time being, a relict aragonitic preservation is put up for discussion. The reason for the di- agenetic history allowing this peculiar kind of brownish pres- ervation of originally aragonitic algae in the Late Cretaceous Lower Subgroup is not known; perhaps factors including continental infl uences and fl uctuations in the salinity and Mg/Ca ratio could have played a role (e.g., RIES, 2006). It is noteworthy, that Miocene to Pleistocene representatives of Halimeda with aragonitic skeletons also show a light to dark brownish appearance in thin-sections (see DRAGAS- TAN et al., 2002). Older representatives of Halimeda, how- ever, show recrystallized, sparitized segments (e.g. BAS- SOULLET et al., 1983), like the majority of the skeletons of fossil dasycladaleans. This should be highlighted with thick and dark-grey letters same manner as on page 43 Remarks on Calcifi cation: From all observations made in the investigated thin-sections from different localities, a hypothetical reconstruction of the thal- lus of Gosavisiphon, with interpretation of variously oriented sections, was made (Fig. 14, except B). It shows that Gos- avisiphon was an epilithic alga growing on hard substrates such as metazoan skeletons or rudistid shells, occurring in Geologia Croatica 63/1Geologia Croatica 44 Figure 10: Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI) from the Randobach, Pass Gschütt area, Upper Santonian (A–E) and the Upper Turo- nian of Noth-Klamm, Gams (F–J). A) Straight to slightly undulating thallus of more or less constant thickness with rounded tip (see detail B), central sp- aritic line (monosiphonal medulla) in the centr (C) or excentric, random (D) and beginning of breakage at the opposite side (see detail E); total length of specimen is 2.1 cm. sample 1791. G–J Curved plates; note varying thickness in (G) and (J), lateral protuberance (arrows in I) with three-layer cortices in the area of a lateral protuberance (close up view of protuberance is shown in (F); plate outline in red). Median plane in (I) is marked in yellow. A B B C C D E F D G H J I Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 45 Figure 11: Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI). A–C Detailed views of laterally fused plates with three- (A, C) and two-layered corti- ces; note the same orientation of the cortices in (B). D, F) Portion of a plate with excentric position of monosiphonal medulla marked in orange, plate outline in red (F, detailed view of D three orders of siphons). E, G) Plate with two swelings (arrows) separated by a constricted portion (G, detailed view of E, white rectangle). H) Mixed siliciclastic-carbonatic microfacies of the Hofergraben tempestite layers with extraclasts (dark), dispersed shell fragments and a fragment of Gosavisiphon gen. nov. in the centre. I) Close up view of (H) (Black rectangle) showing unilateral cortex with comparable long cylindro- conical siphons of diff erent orders (1, 2). J) two fused fragments showing opposite orientation of cortices. A B C D E F G H I J Geologia Croatica 63/1Geologia Croatica 46 soft-bottom substrates, differentiated into a basal prostrate and an erect main part (Fig. 14A). The basal attached part directly follows the contours of the substrate surface, also infi lling small depressions of the latter. In the prostrate part of the thallus, a thin sparitic layer between the unilateral cor- tex, with siphons dividing in direction away from the sub- Figure 12: Basal encrusting part of Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI), Upper Turonian, Noth-Klamm, Gosau of Gams (A–E) and Up- per Turonian of Pletzachalm (F–G). A Crust upon stromatoporoid skeleton, internal siphonal structure barely recognizable. B Crust fragment fi xed to a cavity within the basal substrate. C Specimen fi xed to a stromatoporoid skeleton (dashed line); solid line: upper crust surface. Note the infi lling of the in- traskeletal pores and the erect bending away from the substrate; Crust-sediment boundary solid line, rhizoidal crust outgrowths within the skeletal pores in dashed line. D Specimen fl at encrusting a rudistid shell. E Crust fragment fi xed to substrate; internal siphonal structure well recognizable. F–G Crust fragments fi xed to pelecypod shells. A B C D E F G Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 47 strate, can be observed and interpreted either as monosipho- nal medulla or extracellular cement (Fig. 14D). Then, the alga bends away from the substrate either continuously at a low angle or more abrupt forming the erect part where new fused plates, separated by a thin sparitic line or zone and in- terpreted as extracellar cement/mucilage, occur. Within these fused parts a tri-lateral cortex (Fig. 4G) occurs composed of the unilateral cortex of the basal attached part and the bilat- eral cortex of the newly formed plate. Breakage and displace- ment of the algal plates occurred preferentially along these attachment zones commonly producing fragments with uni- lateral cortices of typical cylindrical to cylindroconical, long and parallel arranged siphons of several orders and reduced intersiphonal spaces (Fig. 14E). An equivalent thin sparitic zone separating adjacent and laterally fused plates also oc- curs in the central part of the plates (?monosiphonal me- dulla?), from which cortical siphons arise in both directions. Depending on the plane of section, the thin central sparitic zone doesn’t always appear centreed (Fig. 14J), is also ob- servable in the parts where plates fuse, and can occupy a random position. The plates are bent along the longitudinal axis and irregularly twisted in the plane of compression (Fig. 14H). As the plates may reach a length of several centime- tres, there are of course several millimetre long straight por- tions. At the slightly swollen tips, the development of a small medulla consisting of several medullary siphons can be ob- served (Fig. 14F); these could also be terminal cortical si- phons. Finally, it must be stressed that it is unkown whether the laterally fused plates all belong to one algal thallus or are just different specimens that use other algal plates as a sub- strate instead of metazoan skeletons or rudistid shells. The fact, that in the fused zones, the internal structure of the main plate changes, can be taken as an indication as being parts of one and the same specimen. Comparisons: The characteristic features of the new genus Gosavisiphon as already discussed also account for its type-species. For instance, the special feature of Gosavisi- phon paucimedullaris with the isolated cortical fragments was also reported from Boueina marondei FLÜGEL (= Hali- meda marondei acc. to DRAGASTAN et al., 1999 = Hali- meda cylindracea acc. to DRAGASTAN et al., 2002) from the Upper Triassic of Thailand (FLÜGEL, 1988). In this spe- cies, post-mortem disintegration was facilitated by a »dis- tinct break in the calcifi cation« between the medulla and the outer cortex. In Boueina marondei, however, the medulla is of comparable width amounting to more than half of the cy- lindrical segments, thus, being totally different from Gos- avisiphon paucimedullaris. Stratigraphy: Specimens of Gosavisiphon paucimed- ullaris (SCHLAGINTWEIT & EBLI) were detected in the Lower Gosau Subgroup within the Middle Turonian to Upper Santonian interval. Within the Branderfl eck Formation it was observed within olistolites of Middle/Late Cenomanian to Early Turonian age. The observed stratigraphic range of Gos- avisiphon is therefore Middle/Late Cenomanian – Santonian. It is most likely that this time interval does not represent its total stratigraphic range, especially at its upper boundary when neritic settings disappeared within the Gosau Group. Palaeoenvironment: Gosavisiphon paucimedullaris grew in sheltered palaeoenvironments of partly sandy uncon- solidated mud associated with calcareous green algae Hali- Figure 13: Brownish calcifi cation in dasyclada lean algae (A–C) and alga incertae sedis (D) asso ciated with Gosavisiphon paucimedullaris (SCHLAGINT- WEIT & EBLI) associated in the tem pestite layers of the Hofergraben, Gosau. A) Jodotella koradae (DIENI, MASSARI & RADOICIC). B) Trinocladus tri- poli tanus RAINERI. C) Neomeris mo kragorensis RADOICIC & SCHLAGINTWEIT. D) Oro seina ple- tza chensis SCHLAGINTWEIT & EBLI (O). A B C D Geologia Croatica 63/1Geologia Croatica 48 me da sp., Neomeris mokragorensis RADOIČIĆ & SCHLAG- INTWEIT, Dissocladella? pyriformis SCHLAGINTWEIT, Terquemella? intermedia PIA, Terquemella? n. sp., Oroseina pletzachensis SCHLAGINTWEIT & EBLI, Thyrsoporella ei- senbachensis SCHLAGINTWEIT & LOBITZER (only at the Eisenbach locality) and benthic foraminifera Vidalina his- panica SCHLUMBERGER, quinqueloculinids, cuneolinids, Tetrataxiella? fl oriformis SCHLAG INTWEIT & SANDERS, gastropods, ostracods and remains of land plants. Within this facies, fi ne grains of pyrite may be present within chambers of benthic foraminifera or algal pores. Gosavisiphon also oc- curs in fl oatstones with debris of rudistids and stromatoporoids (Noth-Klamm, Gams locality). The monotypic assemblage from the tempestite beds within the Santonian Hofergraben Marls, are high-energy accumulations where the plates of Gosavisiphon may show parallel arrangement/orientation (Fig. 9A). These tempestites most obviously accumulated some distance from the original low energy habitat of the alga. It is noteworthy, that epibionts or encrustations were never observed on the algal plates of Gosavisiphon. The mi- crofacies and the accompanying microfauna and fl ora ac- count for a sheltered, terrestrially infl uenced lagoonal setting of presumably nutrient-rich waters, where rudistid bios- tromes occur in lateral association. The strata containing Gosavisiphon paucimedullaris generally follow the basal clastics (conglomerates, breccias, sandstones) of the trans- gressive Lower Gosau Subgroup. 5. CONCLUSIONS Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, being a non-segmented platy siphonous green alga, repre- sents the type-species of the so far monospecifi c new genus Gosavisiphon. It represents a pluricentrimetric Cretaceous seaweed (macroalga) that is so far only known from the Up- per Cretaceous of the Northern Calcareous Alps. It fl our- ished in soft-bottom, terrigeneous infl uenced lagoonal envi- ronments, attached to biogenic hard substrates. The known Figure 14: Hypothetical reconstruction, thin-section interpretation of Gosavisiphon paucimedullaris (SCHLAGINTWEIT & EBLI) (A, C–M), used cortex no- menclature compared to the Permian Anchicodium (B) (explanation in the text). A, C–D, G–J Reconstructions; E) Thin-section showing several series (1–3) of branching fi laments in the cortex. F) tip of a plate. K–M Transverse sections of plate, M) with lateral fusion. A B C D E F G H J I K L M Felix Schlagintweit: Gosavisiphon gen. nov. based on Halimeda paucimedullaris SCHLAGINTWEIT & EBLI, 1998: a remarkable macroalga... Geologia Croatica 49 stratigraphic range is Middle/Upper Cenomanian to Santo- nian. For reasons of pragmatism and taxonomic simplifi cation Gosavisiphon is tentatively placed in the family Udo teaceae and can be excluded as a candidate for the Hali medaceae. With its membraneous architecture it can generally be com- pared with the non-systematic 'phylloid algae' with their dis- continuous appearance in the Late Palaeozoic (Late Carbon- iferous–Early, p.p. Late Permian) and Late Triassic (Norian) reefal platform margin deposits. In contrast to Late Palaeo- zoic aragonitic phylloid algae that were in most cases strongly altered by diagenesis, the specimens of Gosavisiphon exhibit many clearly discernible internal features. With these new fi ndings and interpretation, the stratigraphic record of phyl- loid algae with siphonous internal structures becomes much broader, again witnessing a huge gap in the Jurassic–Lower Cretaceous interval. This offers further possibilites for future discussions, for instance about the phylogeny of the calcar- eous green algae as some Late Palaeozoic phylloid algae were already compared with a few extant taxa of the Udo- teaceae by some palaeontologists. The fi ndings of ovoid fl attened segments of Halimeda sp. in the Middle/Late Turonian of the Lower Gosau Sub- group are the oldest records of this morphological type al- lowing direct comparisons with extant representatives of the genus. So far, comparable segments were not known prior to the Early Tertiary with Halimeda eocaenica MORELLET & MORELLET. Middle/Upper Triassic to Early Cretaceous representatives referred to Halimeda show cylindrical seg- ments with circular cross sections and can, in my opinion, not be directly compared with extant species of Halimeda. This interpretation is completely different from previous as- sumptions, not accepted by all subsequent workers, that the fi rst appearance of the genus is from the Late Permian. Based on the segment morphology as one of the main important features of fossil representatives, the fi rst Halimeda s. str. seems to appear around the Lower/Upper Cretaceous bound- ary, substantiated by the Turonian fi ndings. ACKNOWLEDGEMENT Many thanks to Harald LOBITZER (Bad Ischl), Diethard SANDERS (Innsbruck) and Michael WAGREICH (Vienna) for providing the thin- sections analyzed in the present study. Baba SENOWBARI-DARYAN (Erlangen) and Ioan BUCUR (Cluj-Napoca) are thanked for kindly providing photographs of Anchicodium and allowing their illustration. The picture of modern Udotea has been provided by Tonći GRGASOVIĆ (Zagreb). The reviewers Ivan GUŠIĆ (Zagreb) and Baba SENOW- BARI-DARYAN (Erlangen) are thanked for their detailed reviews and helpful remarks. REFERENCES AGASSIZ, L. (1880): Report on the Florida reefs.– Memoirs of the Mu- seum of Comparative Zoologie at Harvard College, 7, 1–61. BAARS, D.L. (1992): Kansaphyllum, a new Late Pennsylvanian phyl- loid algal genus.– Journal of Palaeontology, 66, 697–701. BASSOULLET, J.P., BERNIER, P., DELOFFRE, R., GENOT, P., JAF- FREZO, M., POIGNANT, A.F. & SEGONZAC, G. 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