Conference Agenda

The Cretaceous was a period of high insect diversity, including numerous orthopteran lineages of which several have become extinct. Five Orthoptera taxa stand out in the fossil record due to their high species number: the Hagloidea, Elcanoidea (lagoon crickets), Locustopsoidea, Grylloidea (crickets) and Tridactyloidea (pygmy mole crickets). The Cretaceous orthopteran fauna is particularly well represented by multiple lagerstätten from around the globe. Especially the Brazilian Crato Formation and amber from Myanmar have yielded numerous discoveries. In our contribution we compare the diversity of Orthoptera found in the Crato Formation and Myanmar amber, especially with respect to the Elcanoidea, Locustopsoidea and Tridactyloidea. Of these three, Locustopsoidea were the dominant group in the Crato Formation by far, whereas they are completely absent from Myanmar amber. Contrary, here the other two groups appear to have been much more diverse. Possible causes for this phenomenon are discussed.

For multiple arachnid groups, such as pseudoscorpions (false scorpions), schizomids (dwarf whip scorpions) and ricinuelids (hooded tick spiders), there were multi-million-year gaps in the fossil record between their first occurrences during the Palaeozoic and fossil findings from the Cenozoic. Cretaceous amber deposits contributed significantly to filling these gaps, though these amber deposits only allow assessing geologically short time intervals. Amber from Myanmar (Burmese amber) is particularly important due to the high arachnid diversity encountered therein. It has allowed us to prolong the known temporal range for extinct groups such as the Uraraneidae (ancient spider-like organisms) or other direct relatives.

In this presentation, we review some recent findings of our own working group and of other researchers, such as the earliest known occurrences of certain arachnid groups and implications for the evolution of these groups, as well as ecological implications. While certain arachnid groups show significant evolutionary development during the Mesozoic, probably in context with the development of angiosperms, forms living in hidden ecosystems such as organic soil or bark seem to have remained in an evolutionary stasis. Problematic aspects of amber-related research are also discussed.

Advanced social behaviour, or eusociality, has been a crucial evolutionary innovation, enabling colonies of ants, termites, social wasps, and bees to achieve ecological dominance over solitary species throughout the Cenozoic. Advanced sociality depends not only on cooperation and division of labor among nestmates, but also on sophisticated communication systems. In this study, we present independent evidence suggesting that Cretaceous ants, preserved in 100-million-year-old amber, were already highly social, based on their chemosensory adaptations. We examine the micro sensory organs of fossil specimens, using original imaging of amber microinclusions, while previous interpretations of fossil ant sociality were often based on individuals preserved nearby. Our analysis revealed an array of antennal sensilla associated with alarm pheromone detection and nestmate recognition, showing distinctive similarities to those in extant eusocial ants. These findings provide direct morphological support for the presence of complex chemical communication and sociality in stem-group Cretaceous ants.

Vitalii Syniehubka

V.N. Karazin Kharkiv National University, Geology department

Keywords: Cenomanian, Turonian, ostracoda, Ukraine.

A number of ostracods of the genus Cythereis Jones, 1849 have been described in the middle Cenomanian and early Turonian deposits of Western Ukraine. The studied deposits were formed in marine basins with different depths and types of bottom substrate. Analysis of ostracod remains made it possible to determine the upper and lower sublittoral zones in both Cenomanian and Turonian deposits. In this way, it was possible to observe the same species of ostracods of the genus Cythereis Jones, 1849 in different palaeoecological conditions.

It was possible to establish that representatives of the genus Cythereis Jones, 1849 have a wide morphological variability in the studied sediments. Against the background of changes in the depth of the sea basin during the Cenomanian-Turonian, patterns of the appearance of morphological adaptations in ostracods depending on the type of bottom substrate are observed. The observed adaptations during the late Cenomanian begin to consolidate and affect speciation from the early Turonian. At the same time, it was possible to collect a large collection of juvenile forms of ostracods of the genus Cythereis Jones, 1849. This made it possible to qualitatively describe the ontogenesis of ostracods and on this basis to construct phylogenetic lines. Analysis of the phylogenetic line made it possible to establish two periods when active dispersal and formation of new species of the genus Cythereis Jones, 1849 were observed.

The use of x-ray microcomputed tomography (micro-CT) for the creation of tridimensional models of fossils has become increasingly common in the last decades. These models allow researchers from all over the world to not only have access to high-resolution images of fossils that would be otherwise difficult to study, but to also observe them in many different angles and easily make different kinds of measurements. For microfossils, which are usually only illustrated at high resolution in a few specific views, micro-CT scanning provides an opportunity for the creation of detailed models to aid in the analysis of different species, particularly of rarer ones. Here we divulge an initiative to create a tridimensional atlas of non-marine ostracods of the lower Cretaceous of Brazil, chosen due to their great relevance for the biostratigraphy of that time period. A total of 152 species have been scanned through micro-CT at the LMPT lab of the Federal University of Santa Catarina (UFSC). Specimens from all selected species have been collected, with 104 having been borrowed from the Naturmuseum Senckenberg, 26 from the Bundesanstalt für Geowissenschaften und Rohstoffe, and 10 belonging to the collection of itt Oeaneon. An illustrated atlas with these 3D models will be made, containing also their taxonomic description, stratigraphic range, biogeography, and scanning electron microscopy images, to provide a complete picture of each specimen. We hope through this project to provide a useful tool for studies involving non-marine ostracods from this important geological period.

Torreites has received only moderate attention throughout the years since its establishment by R.H. Palmer (1933), following its first description from Cuba by Henri Douvillé (1927) nearly a century ago, as Hippurites (Vaccinites) sanchezi. At first glance, Torreites is a peculiarly shaped Late Cretaceous hippuritid rudist bivalve currently subdivided into seven species and based on comparably few and incomplete (type) specimens. Intriguingly, its paleobiogeographic extent is limited to the Caribbean and Arabian provinces – without any other record in the European and North African Neotethys, Pacific, or elsewhere. Therefore, the timing of settlement in the Caribbean and Arabian provinces, respectively, has great potential in understanding circum-equatorial rudist dispersion patterns between the two distant areas.

This highlights the need of a more detailed taxonomic description and morphological understanding of the genus Torreites. This study presents a detailed taxonomic and statistical analysis of close to 300 specimens of Torreites from the Lower Campanian of Saiwan, Sultanate of Oman. The figure of species included in this study by far outnumbers the few dozen globally described specimens, allowing an unprecedented estimation on phyletic relation of the four ‘Arabian’ species. First results reveal a larger interspecific variability than previously assumed that suggests the merger of several of the Arabian species. Furthermore, updated chronostratigraphy of Torreites-bearing strata and refined surface current models narrow the mode of dispersal around the Late Cretaceous equatorial oceans.