Rediscovery of a lost Lagerstätte: a comparative analysis of the historical and recent Mare aux Songes dodo excavations on Mauritius

The Mare aux Songes (MAS), Mauritius, Mascarene Islands, is best known for the remarkable quality and quantity of macro- and micro-fossil remains, including those of the iconic Dodo Raphus cucullatus. It remains the most productive oceanic island fossil locality in the Indian Ocean, and is considered an integrated vertebrate bone Konzentrat-Lagerstätte. Fossil remains were first discovered in September 1865, again in the 1890s and early 1900s, but all without contextual data. The discovery of additional fossil remains in 2005 initiated an international, interdisciplinary research programme in 2006, which resulted in the first contextual analysis. However, it became clearly apparent that the nineteenth- and early twentieth-century fossil collections differed both in taphonomy and in age from late twentieth- and twenty-first-century excavations, and that it was likely that each represented a different depositional setting. Here, we provide evidence for the genesis of the MAS and show that two different fossil deposits were indeed present, each differing significantly taphonomically. Furthermore, the historical material represents a younger, seasonally desiccated, lake-shore accumulation with age range from ca. 1600 yr bp to sub-recent, whereas the 4200-year-old twenty-first-century material is more associated with a deeper, lacustrine environment.