The stratigraphic distribution of larger benthic foraminifera and other microfossils recognizable in thin sections has been investigated in three stratigraphic profiles (Son Maina, S'Heretat and Cuevas de Artà) along the Lower Jurassic shallow-water carbonate platform succession (Es Barraca Member) of the Llevant Mountains in the Mallorca Island. Here, the microfossil assemblage contains abundant benthic foraminifera and calcareous algae, including the microproblematic Thaumatoporella parvovesiculifera (Raineri) and the typical Liassic species Palaeodasycladus mediterraneus (Pia), which has allowed a better age constraint of the succession. Four consecutive biozones (scheme of Septfontaine 1984) have been recognized based on the stratigraphic distribution of imperforate foraminifera, which are documented by the first time in the Balearic Basin: Biozone A (interval Zone) is characterized by the occurrence of small Siphovalvulina sp. and Mesoendothyra sp. and some Lituosepta ancestors. Biozone B (lineage Zone), whose base is marked by the first occurrence of L. recoarensis Cati and the top by the first appearance of primitive forms of Orbitopsella. Biozone B/C1 transition, characterized by the presence of very primitive forms of Orbitopsella. Finally, Biozone C1 (lineage Zone) marked by the first occurrence of Orbitopsella aff. primaeva (Henson) but still with L. recoarensis. This distribution of foraminiferal zones is consistent with a Sinemurian age for the Es Barraca Member, with its top very unlikely penetrating into the Pliensbachian. The proposed biostratigraphic scheme is comparable with those established for other western Tethyan margins such the High Atlas of Morocco and the Betic Cordillera in southern Spain. The reconstruction of the depositional transect across these profiles shows the progressive lost of the upper biozones towards the northeast, evidencing the existence of significant hiatuses in some sections of the Llevant Mountains domain, and allowing to infer an intra-Pliensbachian early stage of platform fragmentation and erosion, or alternatively non-deposition, probably coeval with progradation of deltaic siliciclastics to the northwest part of the Mallorca island. The new biostratigraphic data presented here highlights the need to review and clarify the current stratigraphic scheme established for the Lower Jurassic of Mallorca.

Pal~iont. Z.

AasTgACr: The harder-island system that connects Jerba Island to the Tunisian coastline is composed mainly of carbonate biodasfie sands. Wellpreserved tests of dead epiphytic forantim'fera are abundant on the foreshore and backshore, but they are scattered and poorly preserved on the shoreface, where very fine sand-size eolian quartz, peloids, and broken bioclasts are the main components. The reason for this paradoxical pattern is that most epiphytic foramialfera are very easily removed as suspended load by store-generated currents and concentrated on beaches, washover fans, and small eolian dunes, kilometers away from their" original life environment. Similar bioaccnmulations are common in the fossil record and have often been interpreted incorrectly as prolific biocoenuses.

The microgranular/agglutinated imperforate larger foraminifera (ILF, chiefly "lituolids") of Mesozoic shallow marine carbonate shelves are a polyphyletic group of K-strategists, ecologically homogeneous inhabitants of the photic zone (nutrient poor) and hosting symbionts as their larger porcelaneous recent equivalents. They contrast with deeper water "lituolid" taxa and other deeper marine dwellers (hyaline perforate and planktonics r-strategists). They are narrowly linked to the carbonate platform history and evolution, birth and demise (correlated to paleotectonics or sea-level variations), and global climatic or volcanic events, OAE, etc.2. General principles used in evolutionary sciences can be applied to decipher some morphological pathways among foraminifera through time to reconstruct phylogenetical arborescences, e.g., embryology (heterochronies of development), recapitulation law (Haeckel), size increase (Depéret), parallel evolution, and biostratigraphy.3.Iterative evolution is the main mode of morphological variation through time and biostratigraphy helps to reconstruct the time repartition of diverging advanced homeomorphic taxa and their distinction. The new characters are issued from a constant, more tolerant stock of smaller and simpler primitive atavic forms by the transformation of previous structures or the addition of new ones. Advanced homeomorphic taxa are temporarily preserved and their morphological innovations linked probably to (epi)genetic constraints and symbiotic history increasing their energy efficiency in a rather stable (but cyclical) environment.4.Morphological innovations appear slowly during the Jurassic and more rapidly (and frequently) during the Cretaceous following a probable saltative and allopatric mode of evolution during favorable periods after main environmental crisis, anoxia, and sea-level changes. The Cretaceous is a time of great diversification (adaptive radiation of microgranular lituolids and larger porcelaneous tests).5.Morphological changes at a scale of one or two stages in one evolutive bioseries (general trend: size and internal complications increase) cannot be linked to global events or other abiotic factors (e.g., the orbitopsellids in the Pliensbachian) but are rather driven by internal epigenetic factors related to algal symbiosis and coevolution. The constancy of the model (text Fig. 8.2) through time in variable clades could be explained that way. The structural incompatibility between pseudokeriotheca/alveolae within the wall and marginal microstructures (radial partitions or hypodermic network) could be explained by a biological incompatibility of bacterial symbionts to live aside with larger microalgae as dinoflagellates. Local discontinuous events like cyclic (metric) parasequences are common on carbonate platforms but have no apparent influence on morphogenesis or population composition.6.Conversely, global environmental crises affect deeply the larger foraminifera (chiefly advanced larger tests) and population compositions at a higher taxonomic ...

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