The Shallow Benthic Zonation is one of the most important achievements of biostratigraphy in the last twenty years. Here we summarize the state of the art in the field of Larger Benthic Foraminifera (LBF) and sketch the main lines of research that are improving the precision and usefulness of this scale. The goal of updating the zonation requires a wealth of data coming not only from biostratigraphic investigations but also from paleoenvironmental analyses, biological knowledge, rigorous taxonomic determination, and understanding of paleobiogeography. The papers collected for this special issue are contributions to this broad research program.

The Monte Postale section (Bolca, northern Italy), one of the most famous Lagerstätten of the Eocene, has been investigated to reconstruct the sedimentary succession and to determine both the larger foraminiferal and the calcareous nannofossil biozones. The results allowed us to ascribe the Monte Postale limestones to the Shallow Benthic Zone 11 and to the calcareous nannofossil Zone CNE 5-?6 (= NP 13-?14a). The direct correlation of the SB and CNE Zones is consistent with the current biostratigraphic schemes and allows assignment of the deposition of the succession to the interval between 50.7 and 48.9 Ma, in the late Ypresian (early Eocene). According to the available biostratigraphic data, the uppermost portion of the Monte Postale section should correlate with the Pesciara limestones.

The first identification of Biplanispira in Armenia is of great interest due to the rarity of this genus outside of the Indo-Pacific bioprovince. In the Western Tethys, it had been recorded only from Spain. In the Urtsadzor section of Southwest Armenia, matrix-free specimens of pellatispirids are abundant, allowing a detailed study of their morphology. The aim of this work is therefore the morphological, systematic, and stratigraphic analysis of the genus Biplanispira. The Biplanispira specimens found in Armenia are identified as B. absurda, although they differ from type specimens from Borneo by smaller size of the primary chambers in second and third whorls, higher and more regular spire, larger pillars and development of spiral lateral chamberlets in subequatorial position. The same features are observed in most specimens of B. absurda described from Spain and permit the recognition of two subspecies: B. absurda absurda, distributed in the Indo-Pacific and B. absurda cataloniensis (Matsumaru 1999), found in Armenia and Spain. In Armenia, the stratigraphic range of Biplanispira is restricted to the Bartonian subzones SBZ18B-C in the shallow-water zonation and Priabonian zones E14 and NP19 in the planktonic zonations. The systematic position of pellatispirids between the families Calcarinidae and Nummulitidae is discussed, being closer to the former.

Morphological characters in equatorial sections of planispirally enrolled larger benthic foraminifera were quantified using growth-independent and growth-invariant characters. While the embryonal apparatus (nepiont) is growth-independent, the subsequent chambers change size and shape during growth. Using specific growth stages for grouping (classification) of specimens hinders comparison between species with different growth modes. Here, constants of mathematical functions developed to describe the growth of specific characters are used as growth-invariant attributes. Time, the independent variable, is measured in these functions either by chamber number or revolution angle as a proxy for growth. The complete chamber sequence is not necessary for fitting growth functions: a representative number of chambers enables the equations to be defined. Incompletely preserved tests can thus be used and compared. In addition to former growth-invariant characters previously developed for larger benthic foraminifera, equations describing chamberlets and their change during growth provide a general solution for geometrical reconstruction of tests in equatorial sections. This relieves the need to sort specimens into morphologically-based classes for comparison, which can aid in phylogenetic and paleobiogeographic understanding.

Megalospheric specimens of Heterostegina from four localities in Western and Central Cuba were morphometrically investigated using test characters, which are described by 15 growth-independent and growth-invariant attributes that enable complete test reconstruction in equatorial sections. The species Heterostegina cubana, H. ocalana, and Heterostegina sp. indet. were classified by nonmetric multidimensional scaling and cluster analysis. Discriminant analysis yielded significant separators between species such as the perimeter ratio of the first chamberlets, the decrease in chamberlet length from the previous spiral to the marginal side, the chamber height at the spiral side of the previous whorl, and the proloculus size. Based on a further discriminant analysis, specimens of H. ocalana from different localities, including specimens from Panama, are strongly separated by the number of operculinid chambers, the extension grade of the marginal spiral and the backward bend of chambers, documenting paleogeographic differences and apparent evolutionary trends such as the reduction of the number of operculinid chambers.

In Cuba, Heterostegina is represented by H. cubana and Heterostegina sp. indet. in the Bartonian to lower Priabonian (calcareous nannofossil Zones NP 16-NP 17), while Heterostegina ocalana ranges from Priabonian (nannofossil Zones NP 17 to NP 19-20/CP 15) to probably lower Oligocene (Rupelian) in the lower and middle part of the planktic foraminiferal Zone O 1 (P 18) and in the middle part of the calcareous nannofossil Zone NP 21 (CP 16).

The carbonate system studied represents an under-investigated sedimentary record formed in the western end of the Tethys during the Chattian relatively warm climate regime. These platform carbonates are examined with respect to rock fabrics, biostratigraphy, biostratinomy, paleoecology, and sequence stratigraphy. Dominant carbonate producers include scleractinian corals and echinoids, but the most prolific were symbiont-bearing benthic foraminifera and coralline algae. The presence of Miogypsinoides complanatus and Miogypsinoides formosensis indicates a late Chattian age (Shallow Benthic Zone 23). The depositional profile is consistent with a homoclinal ramp. The absence of a barrier margin and thus, of a lagoon, facilitated the transport and re-working of biogenic components throughout the platform. As a result, facies are rather homogeneous corresponding to a rudstone mainly formed by benthic foraminifera and coralline algae, which passes basinwards to deeper ramp to hemipelagic deposits rich in echinoids and planktonic foraminifera. Within this dominant facies, only subtle and gradual lateral variations on the relative abundance or absence of certain skeletal components or species are recognized, comprising two end members. A proximal biofacies of benthic foraminifera and coralline algae including corals in growth position, fragments of green algae, and seagrass dwellers where Eulepidina, Nummulites, and Operculina are absent, and a distal biofacies where corals, green algae, and seagrass dwellers are not present, but Eulepidina, Nummulites and Operculina are common. Carbonate deposition was controlled by long-term relative sea-level fluctuations including a Rupelian?–late Chattian transgression, a late Chattian regression, which ended in subaerial exposure of proximal ramp carbonates, and a latest Chattian to early Miocene transgression. The Chattian carbonate platform was finally drowned around the Oligocene/Miocene transition.

This study focuses on an Oligocene succession dominated by larger foraminifera and coralline algae in the Benitatxell Range (Prebetic Domain, southeastern Iberian Peninsula). The foraminiferal assemblage, studied in thin sections, and interpreted as Shallow Benthic Zone 23, late Chattian, includes: Austrotrillina asmariensis, Nephrolepidina spp., Eulepidina dilatata, E. elephantina, E. raulini, Amphistegina bohdanowiczi, A. mammilla, Operculina complanata, Nummulites cf. vascus, N. aff. kecskemetii, Heterostegina assilinoides, Spiroclypeus blanckenhorni, Cycloclypeus mediterraneus, Miogypsinoides formosensis, Postmiogypsinella aff. intermedia, Neorotalia viennoti, Risananeiza pustulosa, and Victoriella conoidea.

The Rebaldí section, a succession of late Oligocene limestones 3 km north of the Benitatxell section, shows a similar association with Peneroplis thomasi, A. asmariensis, M. complanatus, Neorotalia viennoti, N. lithothamnica, Heterostegina aff. assilinoides, Spiroclypeus blanckenhorni, Cycloclypeus mediterraneus, A. bohdanowiczi, and Risananeiza pustulosa; it is interpreted as the early part of SBZ 23. This section also contains Praebullalveolina aff. oligocenica, described from the early Rupelian of Turkey, and Schlumbergerina alveoliniformis, previously interpreted as Burdigalian-Recent.

Prior to this work, Cycloclypeus mediterraneus was considered to go extinct and be replaced by C. eidae at the SBZ 22B-23 boundary. However, its presence in the Benitatxell and Rebaldí sections extends its range to the late Chattian in the Eastern Betics and indicates an asynchronous extinction in the Tethys. The presence of Amphistegina mammilla Fichtel and Moll 1798 in late Chattian deposits from the western Tethys contradicts the currently accepted hypothesis that places its origin in the Indo-Pacific province in the early Miocene, from where it would have migrated into the Parathethys during the middle Miocene. In addition, the biogeographic range of P. thomasi, A. asmariensis, and P. oligocenica is extended to the westernmost part of the Tethys.

Morphometric characters of equatorial sections of larger benthic foraminifera have been widely applied to define species for both biostratigraphic and evolutionary studies. In order to test the hypothesis that some of the observed morphological differences may reflect environmental conditions rather than evolutionary changes, we applied morphometric analysis to equatorial sections of megalospheric Heterostegina depressa tests from the reef slope of Sesoko-Jima, NW-Okinawa. Only living specimens were analyzed, thereby eliminating any postmortem alteration of the distribution of H. depressa along the water depth gradient. The analyses clearly differentiated two morphogroups corresponding to two megalospheric generations: gamonts with significantly larger proloculi and schizonts with smaller proloculi. Due to their asexual reproduction strategy, schizonts dominate in high-energy shallower environments. After a transition zone between 35 to 55 m, where both generations are present, schizonts are replaced by gamonts deeper on the slope. Both generations retain the characters of their initial tests regardless of depth. Where both megalospheric generations co-occur, the change in proportion of generations with depth results in an environmental morphological trend that matches apparent fossil evolutionary trends. These results are important for understanding relationships among fossil Heterostegina species, where continuous changes in morphological characters of the initial test part are interpreted as evolutionary trends.