Iberopora bodeuri GRANIER & BERTHOU 2002 (incertae sedis) from the Plassen Formation (Kimmeridgian–Berriasian) of the Tethyan Realm

Microproblematica are microfossils whose suprageneric taxonomic status is unknown. Many microproblematica display an encrusting way of life and can therefore be included in the group of “micro-encrusters” that during the Upper Jurassic were conspicuous components of microbial carbonate crusts (e.g. LEINFELDER et al., 1993; SCHMID, 1996; DUPRAZ & STRASSER, 1999, 2002). These forms are widespread in shallow water platform carbonates where they show more or less pronounced facies sensitivity: that is they can be used in the characterization of certain carbonate palaeoenvironments. However, in contrast, they are only rarely useful for biostratigraphic purposes. In a recent Iberopora bodeuri GRANIER & BERTHOU 2002 (incertae sedis) from the Plassen Formation (Kimmeridgian–Berriasian) of the Tethyan Realm


INTRODUCTION
Microproblematica are microfossils whose suprageneric taxonomic status is unknown.Many microproblematica display an encrusting way of life and can therefore be included in the group of "micro-encrusters" that during the Upper Jurassic were conspicuous components of microbial carbonate crusts (e.g.LEINFELDER et al., 1993;SCHMID, 1996;DUPRAZ & STRASSER, 1999, 2002).These forms are widespread in shallow water platform carbonates where they show more or less pronounced facies sensitivity: that is they can be used in the characterization of certain carbonate palaeoenvironments.However, in contrast, they are only rarely useful for biostratigraphic purposes.In a recent

Iberopora bodeuri GRANIER & BERTHOU 2002 (incertae sedis) from the Plassen Formation (Kimmeridgian-Berriasian) of the Tethyan Realm
Felix SCHLAGINTWEIT contribution, the new microproblematicum Iberopora n. gen.with the type-species Iberopora bodeuri n.sp.was reported from the Berriasian of Portugal by GRANIER & BERTHOU (2002).An adequate description (without generic, species diagnosis) was presented, but little information was provided concerning other occurrences, or facies, and stratigraphic data.As only one reference (the type region) was cited in the synonymy, almost nothing is known about its palaeogeographic distribution.In this discussion regarding Upper Jurassic to Lower Cretaceous material from the Northern Calcareous Alps of Austria and already published in part (SCHLAGINTWEIT & EBLI, 1999) the species was refered to as "Krustenproblematikum" SCHMID, 1996).Here we summarize the available data to provide more complete information concerning this so far poorly known taxon.

GEOLOGICAL SETTING OF THE ALPINE OCCURRENCES
After the drowning of the Upper Triassic shallow water carbonate platform of the Austroalpine shelf (e.g.TOLLMANN, 1985), several lithologies representing deeper water sediments prevailed during the lower and middle Jurassic as, for example, condensed sequences of red and grey limestones and radiolarites (e.g.BÖHM, 1992;GAWLICK, 2000).The reinstallation of a shallow water facies known as the Plassen Formation began in the Kimmeridgian and persisted only into the Lower Cretaceous (Berriasian) in accordance with a proposed model of a compressional regime related to the Late Kimmerian or Eohellenic orogeny (GAWLICK et al., 1999).For a long time it was generally accepted that these shallow water carbonates were deposited on uplifted slide-masses of Hallstatt Limestones with transgressive conglomerates at the base (e.g.TOLLMANN, 1987;STEIGER & WURM, 1980;MANDL, 2000).New investigations have shown that this model cannot be applied to the typelocality Mount Plassen in the Austrian Salzkammergut or to the Krahstein in the Styrian Salzkammergut (SCHLAGINTWEIT et al., 2003b).The deposition of shallow water carbonates in the central NCA began on rising thrusts (e.g.Trattberg Rise) caused by the closure of the Tethyan Ocean and by Late Jurassic nappe

Abstract
Iberopora bodeuri GRANIER & BERTHOU 2002, formerly known as "crust problematicum" (SCHMID, 1996) is described from the Plassen Formation (Kimmeridgian-Berriasian) of the Northern Calcareous Alps (NCA).Here, it occurs either as an incrustation on corals/stromatoporoids or it forms nodular masses ("solenoporoid morphotype").It is typically found in the fore-reef facies of the platform margin, and (upper) slope deposits where autochthonous dasycladales are absent.Water turbulence appears to control the morphological development of Iberopora.Thus, flat crusts appear in less agitated settings.The crusts are almost always accompanied by calcareous sponges/sclerosponges and abundant micro-encrusters, mostly Koskinobullina socialis CHERCHI & SCHROEDER and "Tubiphytes" morronensis CRESCENTI.The stratigraphic range of Iberopora known to date is Oxfordian-Berriasian.In addition to the Northern Calcareous Alps, it has been reported from the epicontinental area of NW-Germany, the northern margin of the Penninic and Tethyan ocean (Slovakia, Switzerland, Spain, Poland, Portugal) and the southern Tethyan domain (Greece, Romania, Yugoslavia).Until other morphological elements (e.g.reproductive organs or protoconch) are found, its systematic position remains uncertain.Currently, it is considered questionably to be an ancestral rhodophyceae or acervulinid-like foraminifera.
In these deposits, the incertae sedis microfossil Iberopora bodeuri GRANIER & BERTHOU has been detected at the Plassen, Krahstein and Trisselwand localities.It is noteworthy that, according to findings at the type-locality and the Trisselwand (SCHLA-GINTWEIT & EBLI, 1999), the Jurassic-Cretaceous boundary can be fixed approximately as within this ultimate marginal facies.
In the following paragraphs, information on the three mentioned localities (Fig. 1) is summarized, along with mention of previous works, data on biostratigraphy and the microfacies of the samples containing Iberopora bodeuri.
At this locality, Iberopora bodeuri GRANIER & BERTHOU (Pl. 1, Fig. 3) is extremely rare and has so far not been found in the platform margin facies of the high-energy Labyrinthina shoals of Upper Kimmeridgian age.The lack of Iberopora there is obviously linked to the absence of prominent coralpatches.Iberopora bodeuri has been occasionally observed in bioclastic upper slope deposits (bioclastic packstones with echinoid remains) that rest on coralbearing limestones at the summit of Mount Plassen.The coralline facies contain foraminifera such as Coscinophragma aff.cribrosa (REUSS) and rarely Trocholina sp. and Protopeneroplis ultragranulata (GORBATCHIK).Dasycladales are represented by Anisoporella ?jurassica (ENDO) and Terquemella ?concavaBERNIER.From the reconstructed synoptic profile, the sample with Iberopora bodeuri can be placed in the lower Berriasian (for further details see SCHLA-GINTWEIT et al., 2003a).SCHLAGINTWEIT et al. (2003b).
Their age is latest Tithonian-Berriasian.Here, only crustose layers of Iberopora bodeuri on fragments of "reef "-builders have been detected, not the nodular masses found at the Krahstein locality.This observation, however, may simply be sampling error.Besides the aforementioned microencrusters, limestones with I. bodeuri contain microbolitic crusts and also the calcareous sponges/sclerosponges with Neuropora lusitanica TERMIER, Peronidella sp. and Cylicopsis sp.

Description
The "skeleton" of Iberopora bodeuri is composed of tiny bubble-like superimposed cells occurring in layers parallel to the substratum.The size of the individual cells ranges from 0.015-0.03mm in width to 0.01-0.02mm in height.The cell (or chamber) wall is a thin micritic envelope; no connection whatsoever between adjacent or superimposed cells has been detected.Thin sparitic layers that occur more or less regularly intercalated in the "skeleton" are a determining characteristic (e.g.Pl. 1, Figs. 2, 5).According to GRANIER & BERTHOU (2002), these "bands of calcite" reach a thickness of up to 0.05 mm.The distance between layers ranges from 0.28 to 0.4 mm.Scrutiny of these "sparitic bands", shows that they are not continuous, but are typically interrupted by small vertical intercalations of "normal" micritic cells (see for example fig. 3 in GRANIER & BERTHOU, 2002).
Characteristically, the upper part (in the direction of growth) is smooth whereas the lower part is irregular, sometimes tapering to form tooth-like shapes.It must also be noted that no sharp boundary (such as the cell wall as in sporangia of coralline algae) exists between the sparitic layers and the micritic cells.
In the Alpine Plassen Formation, Iberopora bodeuri occurs as two morphotypes, one crustose, the other nodular masses.In both morphotypes, no structural differentiation, e.g. a juvenile basal or an adult stage, has been found.The crustose type when attached to larger bioclasts such as corals or "stromatoporoids" may consist of just a few cell/chamber layers (Pl.2, Fig. 5) or attain thicknesses usually ranging between 0.2 and 0.4 mm (Pl. 1, Fig. 2).The other form of typical appearance is nodular masses, the "solenoporoid" morphotype of SCHLAGINTWEIT & EBLI (1999).A digiform branching of the nodules (known for example from Marinella lugeoni PFENDER, see LEINFELDER & WERNER, 1993) has not been observed.The nodules can reach sizes of up to 23 mm in width and up to 17 mm in height (Pl. 1, Fig. 5).The "solenoporoid morphotype" has been observed exclusively in biosparitic limestones, thus indicating water energy as an important ecofactor, its relative strength controlling whether growth is nodular or crustose.Note, however, that the above mentioned sparitic layers occur in both the crustose and nodular morphotypes.No incrustations have been observed between cell layers of Iberopora with any other microencruster except Koskinobullina socialis CHERCHI & SCHROEDER (see also remarks).The surface of the nodular masses, however, may show incrustations by bryozoa or foraminifera.

Discussion
Although it had been figured in the literature (see synonymy), GRANIER (1987) and SCHMID (1996) were the first to pay particular attention to this microproblematicum.The latter described it from the Kimmeridgian of the Lusitanian Basin of Portugal as "crust problematicum".SCHMID (1996 -p.205) remarks on a possible relationship with red algae because of similarities with Lithoporella.The red algae Lithoporella, e.g.L. melobesioides (FOSLIE) has palisade-like, subparallel cells (about 0.046x0.018mm) forming monostromatic layers.Occasionally large conceptacles (up to 0.45 x 0.25 mm) occur (e.g.POIG-NANT & DU CHAFFAUT, 1970;POIGNANT, 1985).Thus Lithoporella differs distinctly and markedly from Iberopora.Some species of coralline red algae have been reported from the Late Jurassic (e.g.IMAI-ZUMI, 1965;JOHNSON & KASKA, 1965) but several authors have expressed serious doubts with respect to the stratigraphic attribution and taxonomic relationships of these taxa (see AGUIRRE et al., 2000).That there is obviously no thallus differentiation speaks against the assignment of Iberopora to "ancestral corallines".Coralline algae are composed of rectangular cell patterns but in Iberopora these cells are superimposed and do not form coaxial rows.Marinella lugeoni PFENDER also shows no thallus differentiation.Recently, the genus Norithamnium under the rhodophyceae, Order Corallinales, was introduced by SENOWBARI- DARYAN et al. (2002) from Upper Triassic reefal limestones.In contrast, SCHMID (1996) also suggests possible affinities of Iberopora with the Palaeozoic cyanobacteria Sphaerocodium (syn.: Rothpletzella), though nonseptate, fan-like arranged and branching filaments typical to Sphaerocodium are lacking (see MAMET, 1991 -p. 428).
GRANIER & BERTHOU ( 2002) offer yet another aspect of the relationship.They note similarities with Solenomeris ogormani (DOUVILLE) (= Acervulina ogormani acc. to MOUSSAVIAN & HÖFLING, 1993), long interpreted as a Solenoporacean alga, now regarded as an encrusting foraminifera (see PERRIN, 1992).Note that the flexibility of growth in Iberopora that creates either crustose layers or nodular masses is in fact also present in acervulinid foraminifera.Validation of evidence for this interpretation, cautiously favoured by GRANIER & BERTHOU (2002), would be the identification of a juvenile stage with embryonic apparatus.As a function of alternations in growth rates, Acervulina ogormani develops layers of small and flat chamberlets intercalated between larger, more rounded chambers (e.g.MOUSSAVIAN & HÖFLING, 1993 -pl. 2, fig. 7).These are indeed somewhat similar to those of Iberopora bodeuri.The main difference is the "wall of hyaline, optically radial calcite, coarsely perforate" of the Acervulinidae (see LOEBLICH & TAPPAN, 1988 -p. 596).These authors state that representatives of the acervulinidae are known from Palaeocene and younger strata.Last but not least, HELM et al. (2003) mention similarities in the structure of Iberopora to those of Wetheredella that may indicate a cyanobacterial origin.

Remarks
The association with Koskinobullina socialis CHER-CHI & SCHROEDER has been mentioned by SCHMID (1996), HELM & SCHÜLKE (1998), DUP-RAZ & STRASSER (1999), SCHLAGINTWEIT & EBLI (1999) and GRANIER & BERTHOU (2002).It is noteworthy that the association with the latter has been observed only in the encrusting, not the nodular morphotype sensu SCHLAGINTWEIT & EBLI (1999).This, however, can also be incidental (a sampling effect).HELM & SCHÜLKE (1998 -p. 86, 98), note transitions between the small chambers of Koskinobullina and "Krustenproblematikum" and a gradational transition between the fossil structures of both taxa.According to these authors (p.98), "these circumstances suggest a colonial plasticity within "Krustenproblematikum" (a small chambered morphotype of Koskinobullina socialis)".The totally different wall structure -calcitic hyaline and perforated in Koskinobullina and microcrystalline calcitic (micritic) in Iberopora bodeuri, however, contradicts such an interpretation.The co-occurrence of two discrete taxa of encrusting organisms in the Upper Jurassic "reefal" facies is probably due to their flourishing in the same favourable environment.Accordingly, the common encrustation can be regarded as another example of biomuration as discussed by CHERCHI & SCHROEDER (1985 -p. 368) for colonies of K. socialis interbedded with corallinacean algae in Middle Cenomanian limestones: "When the colonies are very large, the rhodophycean thalli are, in general, not able to cover the whole surface.In this case, the lateral extension of the rhodophyceans is frequently hindered by overgrowing individuals of K. socialis".It appears most probable that the immuration of K. socialis by Iberopora bodeuri follows the death of the former since it could no longer feed when totally encapsulated by the latter.For further discussion see VOIGT (1970) for a Maastrichtian example involving a foraminifera and a worm-like organism.

Palaeoecology
The lithology and microfacies in which Iberopora bodeuri is found, along with the associated biota, permit the following inferences regarding its palaeoecology.In the Alpine Plassen Formation, I. bodeuri has been found in facies indicating a hard substrate: corals, stromatoporoids or calcareous sponges requiring fixation.Where the platform margin-facies is represented by Labyrinthina shoals as in the Upper Kimmeridgian of Mount Plassen, Iberopora has not been detected.The facies in which I. bodeuri is found can be considered as seaward portions of coral-patches ("Fore-reef ") and upper slope deposits with an association of corals, stromatoporoids and calcareous sponges.Also the co-occurrence of otherwise discrete microbial crusts is worth mentioning.In conclusion, I. bodeuri obviously was not as dependent on light penetration as were dasycladacean green algae (up to -20 m, e.g.MASSE, 1988), and furthermore it has been detected in facies where strictly photophile dasycladales are absent.Where fragments of them do occur under these conditions they are to be regarded as redeposited and allochthonous.In this connection, similarities to modern Cenozoic coralline algae can be drawn (e.g.ADEY, 1976;WRAY, 1979).Together with other microencrusters it occurs in the so-called "Tubiphytes-Koskinobullina association", typically found at the transition from shallower to deeper water facies (SCHMID, 1996 -p. 214).In the Upper Jurassic of Portugal this characteristic association has been referred by SCHMID (1996 -fig. 143) to an inner to middle ramp environment.In NW-Germany it occurs in coral reef facies and according to HELM et al. (2003), I. bodeuri is a pioneer organism that avoids cryptic niches inside coral reef facies thus suggesting a certain dependence on light.In summary, the occurrence of I. bodeuri is facies-dependent and it occurs mainly in reefal (outer infralittoral) and upper slope facies (upper circalittoral -see MASSE, 1988).

Germany
In the Süntel Mountains of NW-Germany I. bodeuri occurs in a coral-microbialite reef of Oxfordian age: the Solenopora biostrome facies sensu HELM & SCHÜLKE (1998).This facies -a parautochthonous biostrome -occurs "above and laterally adjacent to the reef core".Here I. bodeuri is usually intergrown with Koskinobullina socialis CHERCHI & SCHROEDER.HELM (1997) considered that early lithification of the Koskinobullina socialis/"Krustenproblematikum" agglomerates must be assumed because of the presence of borings in its walls.These borings also exist in the Alpine material of the Plassen Formation.

Switzerland
I. bodeuri was reported and figured by DUPRAZ & STRASSER (1999, 2002) from the Oxfordian of the Switzerland Jura Mountains.It occurs in the so-called Röschenz Member that stratigraphically includes the major part of the bifurcatus Zone (Upper Middle Oxfordian) and the lowermost part of the bimammatum Zone (Upper Oxfordian) (DUPRAZ & STRASSER, 1999 -fig.2).Again, the occurrence with the enigmatic encruster Koskinobullina socialis CHERCHI & SCHROEDER was observed in coral-microbialite patch-reefs.Although rare in this habitat when compared with the occurrence of other microencrusters -serpulids, "Tubiphytes" or nubeculariid foraminifera, Koskinobullina-"Krustenproblematikum" occurs most frequently in framestone facies with branching corals.

Slovakia
Here, it occurs in the Stramberk Limestones (Tithonian) of the Outer Flysch Carpathians.It was figured by ELIAS & ELIASOVA (1986 -pl. 8) as Archaeolithothamnium sp.These redeposited boulders came from a former reef belt with corals and calcareous algae typical of reefal/platform margin facies such as Teutloporella socialis PRATURLON and Nipponophycus ramosus YABE & TOYAMA.Iberopora bodeuri is also common in the Stramberk Limestones of the Polish part of the Outer Carpathians (pers.comm.Dr. B. KOLODJZIEJ, Krakow).(1996) was the first to pay particular attention to this encrusting microfossil incertae sedis from the Kimmeridgian.Hesitating to introduce a new taxon, SCHMID (1996) called it "Krustenproblematikum" (crust problematicum) and reported it as generally rare, sometimes with Koskinobullina socialis in mixed coralsiliceous sponge facies and coral-microbolite facies.Another occurrence is from one oncoid formed in a shallow lagoon.In the Lusitanian basin it was recorded as Mikroproblematikum 1 by FÜRSICH & WERNER (1991).Here it is associated with microbial crusts containing a diverse association of microencrusters, and coralline sponges (WERNER et al., 1994 -fig. 10).
The occurrences of Iberopora bodeuri GRANIER & BERTHOU (see synonymy) have been plotted on a palaeogeographic map of the Oxfordian adapted from STAMPFLI et al. (1998) modified to include results from GAWLICK et al. (1999).The map (Fig. 2) shows that this species existed on both shores of Tethys.All occurrences known are in a belt of about 15 to 40º northern latitudes.

CONCLUSIONS
Iberopora bodeuri GRANIER & BERTHOU is a microfossil incertae sedis known from limestones ranging in age from Oxfordian to Berriasian.These limestones were deposited in ramp or carbonate platform environments of the Western Tethyan domain.It is a typical facies sensitive microorganism that occurs in reefal, fore-reefal and upper slope environments where it is associated with a diverse assortment of microencrusters and metazoans (corals, stromatoporoids, and calcareous sponges).

Fig. 2
Fig. 2 Occurrences of Iberopora bodeuri GRANIER & BERTHOU in the western Tethyan realm (simplified palaeogeographic reconstruction of plate boundaries based on STAMPFLI et al., 1998, with integration of the results of GAWLICK et al., 1999).