How long does it take for life to recover after a mass extinction event? According to a new study, it takes at least ten million years before the diversity of living species achieves a similar level to that seen before the mass extinction event. This is according to findings by an international team of scientists who studied fossils from a group of planktic creatures known as foraminifera, or “forams”.

Forams are single-celled microscopic creatures that ooze their way around their tiny worlds. Paleobiologist Karen Wetmore, who was the invertebrate and microfossil collections manager at the University of California Museum of Paleontology for ten years, estimates there are approximately 4,000 foram species alive today (more here).

Forams are primarily marine creatures: most live on or in seafloor sediments, whilst others float around in the water column at various depths. A few species are found in freshwater or brackish environments, and a very few are non-aquatic soil-dwelling species (ref). Most forams create shells out of calcium carbonate (like clams and other shelled animals) or from sediment particles that they’ve cemented together. The shape of these shells are unique to each foram species and can be quite elaborate and beautiful to behold. It’s these structures that can become fossilized.

In this study, paleobiologist Christopher Lowery, a postdoctoral fellow who studies forams at the Institute for Geophysics at the University of Texas at Austin, and his collaborator, paleobiologist Andrew Fraass, a Research Associate in the School of Earth Sciences at University of Bristol, who also is a foram expert, compared the physical complexity of foram fossils and their overall diversity.

“Foraminifera are useful at the species level because of their superior fossil record, so we’ve been able to look at this process in a closer way than anybody else,” said Dr. Fraass in a press release.

When the dinosaurs were wiped out, foram populations were also devastated, but a few species managed to survive. Dr. Lowery and Dr. Fraass studied foram fossils from a time period covering roughly 20 million years, beginning around the end of the Cretaceous mass extinction and extending through the ensuing recovery, to determine how long it took these minibeasts to recover their species diversity (Figure 1).