Spiny ammonites Acrioceras Puzosianum and Crioceras Curnieri, France (Alpes de Haute Provence), Lower Barremian (125 million years), 20xx14 cm (block), 10.5 and 7 cm (height of the two ammonites)

The unrolled ammonites are the most characteristic fossils of Provence, where 80% of the world's species are found. The spines of these ammonites must have played a direct role in protecting them from the large marine predators of the time. The term "uncoiled ammonite" is used for any ammonite whose shell deviates from the "classic" coiling according to a spiral plan with contiguous turns, which is the most frequent mode of development. Long considered an evolutionary degeneration, scientists are now realising that these new shell forms were in fact attempts to adapt to environmental and climatic variations. The aesthetics of these rare specimens make them true natural sculptures.