Architectural complexity of marine crustacean burrows: unusual helical trace fossils from the Miocene of Mallorca, Spain

Abstract

[eng] Unusual helical trace fossils occur in Tortonian shelfal calcarenites in the island of Mallorca. Their morphology may be either simple (ichnogenus Gyrolithes) or, more commonly, consist of two concentric helical burrows (ichnogenus Lapispira). They bear a very characteristic pelleted lining and are associated and probably connected to Thalassinoides and Ophiomorpha burrow systems very abundant in the same unit. These features allow interpreting that the tracemaker was a thalassinidean shrimp. The complex and compound nature of these trace fossils is comparable to that seen in other modern and fossil crustacean burrow systems and it reflects the behavioural plasticity of the architects.