Fossil shark tooth Carcharodon megalodon, USA Collection National Museum of Ireland – Natural History Thomas Clement Thompson, Mrs Reid, wife of Captain Reid of Co. Tipperary, 1799, Watercolour on ivory in a gold pendant, 6.8 x 5.6 cm, Transferred from the National Museum, 1969, National Gallery of Ireland Collection, Photograph © National Museum of Ireland. Photographer: Bryan Rutledge