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Seafood in the Utah desert

Biodiversity patterns, palaeoecology and functional diversity across the "Great Ordovician Biodiversification Event" in the Basin and Range Province, USA

The "Basin and Range" province in the southwest of the USA is popular among fossil collectors. In the US federal state of Utah there are excavation parks: 50 US dollars for three hours of searching for fossils, souvenirs included. Hundreds of fossils can quickly be found in the mechanically excavated rock deposits. Richard Hofmann, paleontologist from the Museum für Naturkunde Berlin, prefers to follow less well-trodden paths for his project.

Hofmann is investigating the "Great Ordovician Biodiversification Event" (GOBE), a sudden increase in species diversity among marine organisms such as crustaceans and arthropods at the beginning of the Ordovician. In this phase of the Palaeozoic from about 490 million years ago to about 450 million years ago, a shallow shelf sea covered the southwest of what is now North America. Approximately 1000 metres of sedimentary rocks with numerous fossils reveal the ecological history of the various marine habitats. In the rugged ridges and valleys of Utah, deposits from different periods are easily accessible.

Species boom in the sea

"I want to find out what happened in the ecosystems and why the diversity of marine species tripled or even quadrupled," says Hofmann. Factors that might have driven the formation of species are shifts in the continental plates, which created new habitats, or climate change.

However, Hofmann is investigating another phenomenon. Competition, for food sources, for instance, as an interspecies factor is more difficult to prove than the effects of environmental changes, which can often be detected in the deposits. But effects of competition become apparent when comparing several ecosystems. In the sea, these include tidal zones, river deltas, reefs, or deeper seafloor.

If animals within such a habitat use the same food sources, such as different species of mussels that filter food from seawater, then over time some species would give way to competitive pressure. Species communities of neighbouring ecosystems would thus diverge. Starting from the relatively uniform marine fauna at the beginning of the Ordovician, their diversity would increase more than the diversity of species within the ecosystems.

Fossil scouts with local knowledge

Hofmann tests his hypothesis of competition as a diversity factor on the basis of hundreds of fossils he finds during his excavations in the Utah desert. The deposits from this time are clearly stratified and one can dig through an almost uninterrupted contemporary history of the Ordovician.

He is supported by two local naturalists: Kevin Bylund and Jim Jenks. He has been working with them for almost ten years and has been able to find many rich sites with their help. There is also a sofa available for the German paleontologist when he is not camping in the desert.

Funding

German Reasearch Foundation -  DFG