Small vertebrates and screen-washing
Methods and collections
Revealing overlooked biodiversity
Excavating a fossil site does not automatically reveal all its fossils. Recovering tiny teeth, scales and bone fragments often begins with collecting the sediment itself.
The method in practice
Samples are labelled with their provenance. After suitable preparation, they are washed through sieves of different mesh sizes. The resulting fractions are dried and sorted under a stereomicroscope. Selected remains are identified, retained and sometimes counted to compare assemblages.
At Angeac and in regional comparisons
At Angeac, screen-washing complements the collection of large fossils, revealing fish, amphibians, small reptiles, mammals and other organisms. After drying, the different fractions are sorted under a stereomicroscope. Each batch retains its provenance label: a tiny tooth loses some of its scientific value if its original layer is unknown.
What this research reveals
Collection methods influence the results. Mesh size, sediment volume and the layers sampled all affect what is recovered. These factors help explain why a group may appear rare and how an inventory expands when the scale of collection changes.
Specimens and data
Sieving reveals very different vertebrates
Small remains include choristodere vertebrae and tiny theropod teeth. Choristoderes are a reptile group distinct from crocodiles and lizards.
Enlarge each plate to examine labels, specimen identifiers and scale bars.
People and expertise
Romain Vullo and Joane Pouech study small vertebrates and their assemblages. Excavators and sorting teams connect sediment sampling with examination and cataloguing.
Further reading
Overview reference: Dinosaures, les géants du vignoble (2017), p. 96–99, 122–123, 166–169.
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