New high-resolution microfossil record from a clay succession in the US Gulf Coastal Plain reveal more accurate age estimates for the critical Eocene–Oligocene transition (EOT), a global climate event marked by the rapid expansion of the first permanent Antarctic ice sheet 34 million years ago. These data suggest a coeval major increase in sedimentation rate. Future isotopic and palaeoecological work on this core can be more precisely integrated with other global records of the EOT.

Changes in morphology during development can have profound impacts on an organism but are hard to quantify as we lack preservation in the fossil record. As they grow by adding chambers, planktic foraminifera are an ideal group to study changes in growth in development. We analyse four different species of Jurassic foraminifers using a micro-CT scanner. The low morphological variability suggests that strong constraints, described in the modern ocean, were already acting on Jurassic specimens.

We used organic-walled microfossils to better define the Plio–Pleistocene transition (2.56 Ma) that is associated with the intensification of the Northern Hemisphere glaciation. The disappearance of species around 2.75 Ma reflects an ecological response accompanying the Greenland ice sheet growth. A strong regionalism marks the Labrador Sea and suggests cooler conditions than elsewhere in the North Atlantic, although our zone boundaries are contemporaneous with the eastern North Atlantic.

To better understand radiolarian evolution and taxonomy, two middle Cambrian specimens recovered from Australia were studied using micro-CT. Analyses of their 3-D models revealed for the first time their skeletal architecture constructed of spicules. Insertion of an artificial sphere into their shells indicates that they may have secreted their spicules one by one during cell enlargement. The timing of skeletal genesis may be an important factor influencing the morphology of early radiolarians.

Diatom assemblages in seasonally sea-ice-covered areas of the Sea of Okhotsk, a marginal sea of the western North Pacific, were investigated. We have selected diatom taxa relating to sea-ice coverage by comparing diatom assemblages in sea-ice, sinking-particle, and surface-sediment samples. The results of the study provide fundamental information for the reconstruction of past sea-ice cover based on ice-algal diatoms in sediments in the Sea of Okhotsk and the North Pacific.