Urban geology: A rostroconch in Hoofddorp

Stephen K Donovan (The Netherlands) Part of my job is to provide service teaching for the University of Leiden. The university lacks a geology department, but my colleagues and I provide tuition in stratigraphy and palaeontology for life science students at the undergraduate and masters degree level. One of my favourite practical classes is a building stones tour of a part of Leiden that is rich in Mississippian (Lower Carboniferous) limestones, which are packed with fossils. These have been used for facing stones, external stairs and paving slabs. Many have been in place for some hundreds of years and many have been etched by slow solution by rainwater as a result. Common fossils include crinoid columnals, tabulate and rugose corals, brachiopods, and molluscs (Donovan, 2016; van Ruiten and Donovan, in review). These are most commonly seen in two dimensions and random sections, a different view of life to what the life scientists are usually accustomed. One group of fossils in these rocks were a mystery until recently, but we now know they are sections through rostroconchs (Donovan and Madern, 2016, p. 349), an extinct group of Palaeozoic molluscs. Rostroconchs were formerly considered to be an ancient group of bivalves and they are certainly bivalve-like in appearance, but lack an articulation of interlocking teeth and a ligament. That is, the shell is a univalve, a one-piece structure. I had only seen the sections of rostroconchs in building stones in Leiden. It was therefore gratifying, shortly after publication of these fossils, to … Read More