Polyphysaceae fertile caps in Hungarian Sarmatian sediments

Three fragments of reproductive caps have been discovered in the Sarmatian limestones of Tinnye (Hungary). They are assigned to the genus Acetabularia (Polyphysaceae, formerly Acetabulariaceae). Two of these fragments are quite well preserved with nine rays each. One specimen bears distinct spines at the outer ends of long rays, whereas another one has short rays with rounded outer ends and, possibly, a partially preserved corona. The third fragment is characterized by very elongated rays containing numerous gametangia.


INTRODUCTION
The Polyphysaceae (Dasycladales) studied in this paper were discovered in the Upper Sarmatian Tinnye Formation, defi ned at Tinnye, a village located in the Zsámbék Basin, about 30 km west of Budapest (Fig. 1).Specimens have been found in limestones with oolitic grapestones, microbial features encrustations and crustose foraminifera, within oolitic sandstones series (Fig. 2).Due to rarity of these fossils, their occurrence merits description and illustration.
There is a pattern of large oolitic and bioclastic shoals in the Zsámbék Basin, on top of which bio-constructed facies and encrustations developed.

PALAEONTOLOGICAL DESCRIPTION
Specimens from Tynnie consist of three fragments of fertile caps lying on a limestone surface.Two of them are quite well preserved with nine cap rays fi rmly held together by strong calcifi cation.
Specimen 1 (Fig. 3) Nine cap rays can be observed on this specimen.The entire cap of the living alga was probably composed of 14 rays.The most remarkable feature of this species is the distinct spines at the outer ends of the rays.The gametangia are not visible.
Diameter of the cap: 4.45 mm.Length of the rays: 1.75-2 mm (approximate data because of the poor preservation of the cap central zone).
Specimen 2 (Fig. 4) The fragment of this small cap is composed of nine rays.The estimated initial number of rays is 14 or 15.Cap rays are short.Their outer ends seem more or less rounded but it is not pos-sible to confi rm this because of the poor preservation of the peripheral outline of the cap.For the same reason, it is difficult to know if the circular swelling, located at the proximal ends of the rays, in the central area of the cap, is a partially preserved corona.Longitudinal sections of three rays show 5 to 8 hemispherical cavities corresponding to the location of the gametangia.There are only 2 to 3 laterally juxtaposed game tangia in the widest part of the ray.The estimated number of gametangia inside each fertile organ is 8 to10 (but may be 16-20 if gametangia were arranged in 2 superimposed planes, that are diffi cult to determine on the specimen).
Specimen 3 (Fig. 5) The third specimen is composed of fi ve very partially preserved cap rays.It looks different from the previous one: rays are elongated and contain numerous rounded gametangia, probably more than 40 in each organ.There are 4 to 5 laterally juxtaposed gametangia in the widest part of the ray.Approximative length of the rays: at least 2.6 mm.Maximum width of the rays: at least 1.1 mm (only 2 rays can be measured).

GENERIC ATTRIBUTION
We adopt here the generic concepts recently defi ned by BERG-ER et al. (2003), after a detailed study of the phylogeny and evolution of cap development in living Polyphysaceae (formerly Acetabulariaceae).Using a combination of morphological, developmental and molecular characteristics, the authors consider Acicularia as "…completely identical in its morphology with Acetabularia" and show that earlier stages of cap development are very similar in both genera.The only difference concerns the calcifi cation: gametangia are embedded into a lime matrix in Acicularia, whereas gametangia are uncalcifi ed and free in Acetabularia, but the authors demonstrate that lime-embedding of gametangia is in fact, a late developmental event of maturing caps.Therefore, they assign the living Acicularia species (A.schenckii) to the genus Acetabularia.
Fi gu re 3: Specimen 1 -external view of a partially preserved cap.
Fi gu re 1: Location of the Zsámbék Basin.
Acetabularia, containing A. acetabulum, characte rized by "congenitally fused cap primordia".There is no mention of the calcifi cation in these defi nitions.So, Acetabularia is now the only genus of the Recent Polyphy saceae (formerly Acetabulariaceae) including species bearing fertile caps with gametangia embedded into a lime matrix (Fig. 6).If palaeontologists adopt these new generic concepts, it would be coherent to assign all fossil species of Acicularia to the genus Acetabularia.This is why the three fertile caps studied in this paper are considered as Acetabularia.
Associated rays forming caps are also known in the following genera: -Orioporella MORELLET & MORELLET, characterized by its hollow caps with perforated walls and partially calcifi ed gametangia; -Chalmasia SOLMS-LAUBACH, with strongly calcifi ed gametangia but which are free inside the rays; -Parvocaulis BERGER et al., with uncalcifi ed ga metangia.Another feature may be observed in these genera (Fig. 6): the presence of lower and upper coronae in Acetabularia, a corona only on the upper side of the cap in Parvocaulis and Chalmasia.But this morphological characteristic is almost never observed on fossils, even when the specimens Fi gu re 4: Specimen 2 -external and internal views of a partially preserved cap.
Fi gu re 5: Specimen 3 -location of gametangia inside two cap rays.
Fi gu re 6: Some features of caps in present-day Polyphysaceae (data from VALET, 1969;BERGER & KAEVER, 1992;BERGER et al., 2003;BERGER, 2006).may be entirely isolated from the sediment (GENOT, 1987).The corona zone is often badly preserved and when the specimens are lying on a limestone surface, only one side of the cap can be studied (MORELLET, 1939).This is the case for specimen 2.

COMPARISONS
Polyphysaceae fertile caps have already been discovered in Sarmatian limestones from Hungary, near Ecseg (BODA, 1959).The author assigned to a new species, Acicularia conica, different specimens which, in fact, belong to distinct species (see the discussion in BUCUR et al., 1993).Among these specimens, two of them are reproductive caps lying on a limestone surface (ibid., pl.44, fi g. 1-2).The most complete specimen is an entire cap composed of 25 rays.The rays look much more elongated, compared with our specimens 1 and 2. Unfortunately, the comparison cannot go further because the outline of the caps is badly preserved and the internal aspect of the rays remains unknown.
The presence of spines at the distal ends of the rays, observed on specimen 1, is known in present-day species, such as Acetabularia crenulata LAMOUROUX, A. dentata SOL-MS-LAUBACH (Fig. 7a) and A. kilneri AGARDH (Fig. 7b).But this is the only common feature with the Sarmatian caps: the rays are much more elongated in A. crenulata and A. kilneri (VALET, 1969;BERGER & KAEVER, 1992;BERGER, 2006).
Specimen 2 bears, at the centre of the cap, a fragment of a circular swelling which might be a corona.Despite the exceptional occurrence of this feature on fossils, it has already been possible to describe a rather well preserved corona on Sarmatian Acetabulariaceae from Romania (GÉNOT et al., 2002) with the characteristic protuberances (ibid., pl.III, fi g.2) on which branched sterile hairs develop in living representatives.These protuberances are unknown on the Hungarian specimen.Concerning the cap rays, only one Romanian specimen (ibid., pl.III, fi g.1) has similarities with specimen 2: short rays containing a small number of gametangia.

CONCLUSION
Hungarian specimens from Tinnye probably belong to Acetabularia, because of the strong calcifi cation fi lling the spaces between the gametangia.This type of calcifi cation is unknown inside the fertile caps of the other genera of Poly physaceae.
Concerning the specifi c attribution of these three specimens, we consider that is not possible, with a so small number of partially preserved fossil caps, to determine if they may be assigned to previously described species or if they correspond to new ones.Thus, more samples would be necessary to precisely establish the morphological features of these species, so as to avoid future confusion in the literature.