Current research

The following subjects are currently under investigation. General topics and preliminary results are mentioned as well as the state of progress 

Miocene holoplanktonic molluscs from the Maltese archipelago

More than a hundred sediment samples of up to 20 kg, taken from Maltese Cenozoic deposits (Lower Globigerina Limestone Member to and including Greensand Formation) yielded 85 species of holoplanktonic molluscs (Gastropoda, ‘Heteropoda’ and ‘Pteropoda’), 16 of which had to be classified in open nomenclature or with a query. Of the 85 species nine belong to the Pterotracheoidea, 66 are Thecosomata (Euthecosomata), five are Thecosomata (Pseudothecosomata) and another five are Gymnosomata. The following species are introduced: Protatlanta kbiraensis sp. nov., Carinaria maempeli sp. nov., Heliconoides wardijaensis sp. nov., Limacina ernstkittli sp. nov., Creseis curta sp. nov., Styliola schembriorum sp. nov., Johnjagtia baharensis sp. nov., Clio merijni sp. nov., C. vilis sp. nov., Cavolinia gatti sp. nov., C. microbesitas sp. nov., Diacrolinia pumilionis sp. nov., Gamopleura pilula sp. nov., Peracle amberae sp. nov., P. grebneffi sp. nov., Genus Clionidarum ignotus sp. nov., Genus Clionidarum imdinaensis sp. nov., Genus Clionidarum phosphoritus sp. nov., Genus Clionidarum tripartitus sp. nov. and Genus Clionidarum tumidulus sp. nov. An extensive description of sampled localities in Malta and Gozo is given. In the systematic part synonyms, descriptions, locality listings and discussions are given for all species. The recognized holoplanktonic mollusc assemblages are applied in a chronostratigraphical interpretation of the various rock units (Chattian to Tortonian) and are the basis for a biostratigraphical zonation for the Maltese Archipelago, based on pteropod species, constructed in comparison with similar zonations valid for the North Sea and Aquitaine basins. An extensive comparison with published and unpublished pteropod occurrences elsewhere in the Mediterranean realm results in a preliminary pteropod biozonation valid for the entire Mediterranean (Late Oligocene-Early Pleistocene). In an appendix some notes are given on fossils other than holoplanktonic molluscs obtained from the analyzed samples.

Submitted (October 2010) to Museo Regionale di Storia Naturale, Bolletino.

Late Quaternary to Recent holoplanktonic Mollusca (Gastropoda) from bottom samples of the eastern Mediterranean Sea: systematics, morphology

Holoplanktonic molluscs of 62 bottom samples and the sieving residues < 0.6 mm of a single gravity core, were evaluated. The total number of species found in all samples together is 49 (Pterotracheoidea 11, Janthinidae 2, Limacinoidea 5, Cavolinioidea 16, Cymbulioidea 8, Gymnosomata 5, incertae sedis 2).

Results obtained from the residues of bottom samples only give information about which species have been present in the roughly estimated interval 'Late Pleistocene to Holocene, Recent included'. The gravity core samples were previously dated on the basis of planktonic Foraminifera, comprising the interval of latest Saalian to Holocene, and some more detailed information on the vertical distribution of the species could be obtained. Construction of a 'palaeoclimatological curve', as done by numerous earlier authors, was not attempted. In the systematic part a neotype is designated for Atlanta keraudrenii Lesueur, 1817, and a lectotype for Steira lamanoni Eschscholtz, 1825, making both taxa to junior synonyms of Atlanta peronii Lesueur, 1817. Clio pyramidata f. tyrrhenica nov. f. is introduced. For many species morphological details and questions concerning systematics and/or nomenclature are discussed, in various cases also related to the desired position of a taxon at species, subspecies, or infraspecific level.

Submitted to Bollettino Malacologico.

Further holoplanktonic molluscs from the Fiji Islands

Additional to the material from the Fiji Islands discussed in an earlier paper (Janssen, 1999b) on the Buton fauna (Indonesia) a collection of heteropods and pteropods was made available by the late Mr Andrew Grebneff (Dunedin, New Zealand). This material contains interesting new information on the Cenozoic Pacific assemblages.

Publication expected 2012.

Pliocene holoplanktonic Mollusca from the Mediterranean area

A considerable material is available from various localitities in Italy, France and Spain. Long term project ! Publication will take several years. Material recently made available from the Estepona area (Málaga, Spain) was published separately.

Publication ?

Cainozoic pteropoda from the North Sea Basin

A substantial material, both from outcrops and boreholes, housed in many public and private collections is studied gradually. Manuscript (2001) comprising over 50 pages already, but only part of the material is sufficiently investigated yet. Numerous species of pteropods, biostratigraphical results, long distance correlations ...

Publication .... ????