Neogyroporella? gawlicki n.sp., a New Dasycladale from the Upper Jurassic–Lower Cretaceous “Lärchberg Formation” of the Northern Calcareous Alps, Austria

The Upper Jurassic to Lower Cretaceous shallow water platform carbonates of the Northern Calcareous Alps (Plassen Formation, “Lärchberg Formation”) and the resedimented deposits of the latter within basinal series (Barmstein Limestone, Tressenstein Limestone) are currently under re-investigation (SCHLAGINTWEIT et al., 2003; GAWLICK et al., 2005). This shallow water development is directly linked to tectonic activity in the Western Tethyan domain causing early nappe formations (GAWLICK et al., 1999; FRISCH & GAWLICK, 2003). Already in the Middle Jurassic, the geodynamic and sedimentological framework was mainly governed by the closure of parts of the Tethyan ocean leading to the first thrust nappes and the formation of a rise-andbasin pattern (e.g. GAWLICK et al., 1999). Starting in the southern parts of the Northern Calcareous Alps, the compressional tectonic regime governed uplift processes producing shallowing-upwards successions from basinal to external and finally internal carbonate platform deposits. In the same way as there were different Neogyroporella? gawlicki n.sp., a New Dasycladale from the Upper Jurassic–Lower Cretaceous “Lärchberg Formation” of the Northern Calcareous Alps, Austria


INTRODUCTION
The Upper Jurassic to Lower Cretaceous shallow water platform carbonates of the Northern Calcareous Alps (Plassen Formation, "Lärchberg Formation") and the resedimented deposits of the latter within basinal series (Barmstein Limestone, Tressenstein Limestone) are currently under re-investigation (SCHLAGINTWEIT et al., 2003;GAWLICK et al., 2005).This shallow water development is directly linked to tectonic activity in the Western Tethyan domain causing early nappe formations (GAWLICK et al., 1999;FRISCH & GAWLICK, 2003).Already in the Middle Jurassic, the geodynamic and sedimentological framework was mainly governed by the closure of parts of the Tethyan ocean leading to the first thrust nappes and the formation of a rise-andbasin pattern (e.g.GAWLICK et al., 1999).Starting in the southern parts of the Northern Calcareous Alps, the compressional tectonic regime governed uplift processes producing shallowing-upwards successions from basinal to external and finally internal carbonate platform deposits.In the same way as there were different Neogyroporella?gawlicki n.sp., a New Dasycladale from the Upper Jurassic-Lower Cretaceous "Lärchberg Formation" of the Northern Calcareous Alps, Austria Felix SCHLAGINTWEIT basins with cherty sediments ("radiolarite basins"), the new results show that there was not only one, but several independent areas with shallow water carbonates within the former deeper-marine area (e.g.KÜGLER et al., 2003 -fig. 3;FRISCH & GAWLICK, 2003;GAWLICK & FRISCH, 2003 -for further details, and unpubl. data).
Current research should help to increase the precision of existing palaeogeographic and geodynamic interpretations and models.However, there is still a lack of knowledge of the micropalaeontological composition of these platform carbonates, in contrast to the comparably good data base of the Alpine Triassic.In the course of recent biostratigraphic and microfacies analyses of the Alpine "Upper Jurassic" platform carbonates, a Dasycladacean alga, that has already been figured several times from the Northern Calcareous Alps since the early 1990's as Macroporella praturloni DRA-GASTAN, has been recognized as a new species and is established as Neogyroporella?gawlicki n.sp.

GEOLOGICAL SETTING
In the Salzburg Calcareous Alps, near the German-Austrian border, there are several isolated occurrences of shallow water limestones known as the "Lärchberg Formation" (FERNECK, 1962), currently a non-formalized unit.For a long time, these carbonates have been assigned to the Triassic, e.g.Dachstein Limestone, and it was FERNECK (1962) who first recognized their Upper Jurassic-Lower Cretaceous age.He proposed the subdivision of the "Lärchberg Formation" into two parts: a clastic basal complex (Lofer beds or L. member) and the Lerchkogel Limestone.These lithologies have been referred to in the works of FERNECK (1962), DARGA &SCHLAGINTWEIT (1991) andDYA (1992).Another Upper Jurassic carbonate platform evolutionary series in the Northern Calcareous Alps is known as the Plassen Formation, with the typelocality Mount Plassen near Hallstatt in the Austrian Salzkammergut (e.g.TOLLMANN, 1976).In contrast to the latter, the "Lärchberg Formation" partly shows a terrigenous influx unknown from the former.However, detailed discussions on their possible correlation are beyond the scope of this paper.The marly limestones of the "Lärchberg Formation" are characterized by a rich assemblage of Dasycladales together with "stromatoporoids", benthic foraminifera and cyanophycean algae.In some parts, representatives of the protohalimedacean alga Pinnatiporidium (sensu DRAGASTAN et al., 2002) are dominant and can be termed Pinnatiporidium wackestones to floatstones.These lithologies yielded the new Dasycladale Neogyroporella?gawlicki n.sp.detected at the Dietrichshorn and Litzelkogel (Fig. 1).
The marly limestones containing the new alga outcrop near the summit of the Litzelkogel (1625 m a.s.l.), which forms a plateau-like mountain, together with the Gerhardstein (1541 m a.s.l.-Fig.2).Due to sporadic outcrops and vegetation as well as steep flanks bordering the plateau, a lithological profile cannot be provided.According to DYA (1992), the "Lärchberg Formation" of the Litzelkogel-Gerhardstein has a thickness of about 250 m.Neogyroporella?gawlicki n.sp.was figured by DYA (1992 -Profile 11) as Macroporella?praturloni DRAGASTAN (see synonymy below) from the northern part of the Gerhardstein-Litzelkogel plateau.Detailed sampling carried out in recent times, has shown that Neogyroporella?gawlicki n.sp. is missing at the Gerhardstein.Here, the youngest sediments exposed can be attributed to the uppermost Kimmeridgian or lowermost Tithonian due to subaerial exposure (unpublished data).

SYSTEMATICS Order Dasycladales
Tribe Salpingoporelleae Genus Neogyroporella YABE & TOYAMA, 1949 Remarks: As will be discussed below, we tentatively assign our specimens to the genus Neogyroporella YABE & TOYAMA.The genus Neogyroporella with the type-species Neogyroporella elegans has been established by YABE & TOYAMA (1949), from the Upper Jurassic Torinosu Limestone of the Sakawa Basin, Japan.The age of the Torinosu Limestone, previously referred to the Oxfordian-Tithonian interval, has more recently been precisely dated as Tithonian-Berriasian (e.g.OHGA & IRYU, 2003;SHIRAISHI & KANO, 2004).Therefore the exact stratigraphic position of Neogyroporella elegans is not known in detail.Neo- Although never discussed previously, another genus very similar to Neogyroporella is Humiella SOKAČ & VELIĆ (1981), with the type-species Humiella catenaeformis (RADOIČIĆ) from the Neocomian of Southern Herzegovina.In fact, representatives of Humiella are characterized by alternating fertile laterals (ampullae), closed at the tips which are of variable shape (mostly bulbous).In both the original description, and others, "a thin corticular envelope enwrapping the soft parts of the plant" has been proposed by SOKAČ & VELIĆ (1981 -p.104) as the main generic characteristic.This feature has also been remarked for Neogyroporella by YABE & TOYAMA (1949 -"surface is covered by a thin calcareous crust").Later, the main characteristic of Humiella was said to be represented by tiny pores or indentations in the calcareous wall of the laterals with the main axis corresponding to sterile laterals (MASSE et al., 1984;SOKAČ, 1987).In fact, these "pores" or indentations (= "kleine Zähnchen" -OTT & FLAVIANI, 1983) obviously only seldom cut through the whole wall and can therefore be termed "blind pores" as described from the genus Drobnella BARATTOLO, 1998 (Chlorophyta or Charophyta).The existence of such blind pores or real pores, however, is not clearly observed in the specimens from the Northern Calcareous Alps.Due to strong recrystallization the boundary between adja- cent calcite crystals may suggest a finely perforated wall (diagenetic origin!).This uncertainty has been the reason to only tentatively refer these specimens to the genus Neogyroporella.However, if a re-investigation of the type-material of Neogyroporella elegans YABE & TOYAMA shows both types of pores in the calcareous walls, as could perhaps be assumed in, for example, fig. 5 from YABE & TOYAMA (1949) and any kind of corona structure is absent, the genus Humiella would become very close to Neogyroporella or perhaps even a synonym of the former.
Finally, it should be mentioned that the genus Humiella has been included in the tribe Clypeineae with "verticilles espacés" by DELOFFRE (1988).The genus Humiella, however, includes both species with well spaced-out verticals, such as Humiella sardiniensis (OTT & FLAVIANI), or forms with closely packed touching laterals, such as Humiella japodica recently described by SOKAČ (2001) from the Lower Jurassic of Croatia.For the Clypeina species with slightly touching whorls ("overlapping whorls"), the genus Similiclypeina has been established by BUCUR (1993).
Last but not least, the systematic framework becomes more complex as the genus Humiella SOKAČ & VELIĆ has been regarded as a synonym of Sarfatiella CONRAD & PEYBERNES by CONRAD (1982).Sarfatiella, however, is treated as a synonym of Holosporella PIA by BASSOULLET (1987) and by GRANIER & DELOFFRE (1993).The whole brief discussion of current taxonomic incongruencies is not pursued further here; it is just mentioned for completeness, but it also expresses the uncertainties we have in the systematic attribution of these specimens (see also Type-locality: Litzelkogel, Topographic Map of Austria ÖK 92 sheet Lofer, marly limestones cropping out in the area of the summit (Fig. 2).The location of the summit of the Litzelkogel is 12º46' geographic longitude and 47º38' geographic latitude.
Material: One thin-section containing about 30 specimens from Mount Dietrichshorn and several thin-sections each with 2-5 specimens from Mt. Litzelkogel.Holotype: Oblique-tangential section figured on Pl.I, Fig. 5, thin section labelled A-190 (exact location see Fig. 2).The material from the Litzelkogel is stored at the "Institut für Geowissenschaften, Universität Leoben".Isotypes are represented by different sections shown in Pls.I-III.
Diagnosis: Thallus euspondyl, cylindrical with a comparable small main axis and numerous elongated, gently broadening laterals with swollen endings.The laterals, closed at tips, are arranged more or less perpendicular or slightly inclined to the axis.The microstructure of the individual calcified sheaths enclosing the laterals has a fibrous appearance.The whorls are close-set with alternating laterals touching those from adjacent whorls.
Description: Thallus simple and cylindrical.The axial cavity is comparatively small, most frequently comprising 27-30% of the total diameter.The simple, undivided and elongated laterals communicate with the axial cavity by means of narrow connecting pores that broaden gently, then swell into sphere-like distally closed ends.The arrangement of laterals in consecutive whorls is alternating.The main axis and the laterals are each covered with their own thin calcareous envelope.Due to secondary calcification, the laterals are in contact at their proximal parts.At the most distal parts, adjacent laterals are not in contact with each other.The outer part of the thallus is composed of the distal ends of individual laterals of alternating arrangement; the inner surface of the thallus is straight.The laterals are slightly inclined to the axis at an angle between 5 to 15º.
In tangential sections, the laterals appear as a rounded pore meaning that they are neither longitudinally nor transversally compressed.Although cysts have not been observed in our specimens, the swollen laterals suggest a cladosporous type of reproduction.

Remarks:
The species in question has repeatedly been confused with Macroporella praturloni DRAGASTAN (see synonymy).In fact, the laterals with individual calcareous sheets are very similar in tangential sections and also the d/D ratio is the same.M. praturloni, however, is on the whole different from Neogyroporella?gawlicki n.sp.by possessing phloiophorous laterals, open at the tips and distinctly inclined to the axis.Additionally, M. praturloni is much larger than N.? gawlicki n.sp.with a thallus diameter reaching up to several millimetres (see also BUCUR, 1985 -table 1).
The only species to which Neogyroporella? gawlicki n.sp.can be compared to is the type-species N. elegans YABE & TOYAMA.Generally, this new species can be regarded as a "mini version" of the latter.N. elegans is distinctly larger than N.? gawlicki n.sp.(see Table 3).The d and D values do not show any overlapping areas but are distinctly separated from each other.Thus, both species are clearly individual due to their dimensions.In addition, the type-species possess a lower number of laterals (w, see Table 3) which more or less thicken at their proximal parts.In addition, a second taxon has been briefly recorded by YABE & TOYAMA (1949) as Neogyroporella sp. from the same locality as N. elegans.While being distinctly larger than N.? gawlicki n.sp., the number of laterals per whorl (~34) approach the maximum value measured for N.? gawlicki (~26) (see Table 3).

Stratigraphy:
Based on the aforementioned microfossil assemblages and results of previous and recent investigations, the samples containing Neogyroporella?gawlicki n.sp.can be assigned to the Late Tithonian or Early Berriasian.The evaluation of the total stratigraphic range, however, cannot be established reliably and surely needs further data.In this connection it should be mentioned that Neogyroporella?gawlicki n.sp.has not been detected in the samples of the Gerhardstein where the youngest sediments match the Kimmeridgian-Tithonian boundary or the earliest Tithonian.However, the marly limestones containing Neogyroporella?gawlicki n.sp.which crop out at the Litzelkogel summit represent the final part of the exposed succession.

Facies and palaeoenvironmental interpretation:
The marly limestones that crop out around the summit of the Litzelkogel (see Fig. 2  n.sp.may be assigned to a sheltered "back-reef" environment with terrigenous influence (siliciclastic detritus, terrestrial?plant remains).
At the Dietrichshorn locality, the co-occurrence with Zergabriella embergeri (BOUROULLEC & DELOF-FRE) may point to freshwater influences (CONRAD, 1977).Indications of a very shallow water setting with signs of subaerial exposure are indicated by components showing circumgranular cracking sensu ESTEBAN & KLAPPA (1983).
For Neogyroporella elegans, YABE & TOYAMA (1949) did not give comments on the facies or associated microflora and microfauna, but the illustrated figurations show a micritic microfacies (wackestones) indicating a quiet water setting.Thus, the Torinosu Formation does not only comprise reefal facies (SHIRAISHI & KANO, 2004) but also lagoonal facies, as indicated by the occurrence of wackestones with Cladocoropsis mirabilis FELIX (YABE & TOYAMA, 1927).

CONCLUSIONS
Neogyroporella? gawlicki n.sp.represents another species of the so-far poorly known genus Neogyroporella YABE & TOYAMA.It occurs in marly limestones of the "Lärchberg Formation" of Late Tithonian or Early Berriasian age.This terrigeneously influenced lithofacies, rich in calcareous algae has up to now not been recorded from the Alpine Plassen Formation.

Fig. 1
Fig. 1 Generalized geographic sketch map of the localities where the new Dasycladale Neogyroporella?gawlicki n.sp.has been detected.

Fig. 2
Fig. 2 General position of the sample localities with Neogyroporella?gawlicki n.sp. at the Litzelkogel type locality.The sample A-190 contains the holotype.

Table 1 ). Neogyroporella? gawlicki n.sp.
Origin of the name: Dedicated to Prof. H.-J. Gawlick, University of Leoben, in recognition of his stimulating new concepts and ideas concerning the geodynamic evolution of the Alpine Jurassic.