A new Miocene deep-sea chiton and early evidence for Teredinidae-sustained wood-fall communities

Abstract

Deep-sea wood-falls are important biodiversity hot spots for insights on chemosynthesis-based communities. The study of deep-sea wood-fall-related palaeocommunities from the Neogene of north Italy shed light on interesting associations from the Miocene of Torrente Cinghio (Tortonian) and of Moncasale di Casina (Langhian). The most common components of this association are typical chemosynthetic/wood-fall molluscs, such as the gastropods Homalopoma sp. and Pseudonina bellardii, the bivalves Idas sp. and shipworms, and the chiton Leptochiton lignatilis n. sp., which belongs to a genus typical of recent sunken woods in tropical waters. The new species described is compared with other fossil and recent congeners, especially with those sharing the same kind of tegmental sculpture, fully covered with randomly or quincuncially arranged granules. An overview of the sunken wood-related chitons is provided. Surprisingly no taxa of the boring bivalves of the family Xylophagidae, whose species have been known to be fundamental for sustaining this kind of deep sea chemosynthetic ecosystem, were found in the studied site; however, other boring Teredinidae bivalves have been abundantly recovered. This suggests that, conversely to what has previously been observed on sunken wood communities, Teredinidae may be viewed as a counterpart for the maintenance of deep-sea wood-fall ecosystems.