Life-position succulent Euphorbia L. fossils buried in Pleistocene explosive volcanic deposits from Tenerife, Canary Islands, Spain

Great volumes of tephra released during past Plinian volcanic eruptions catastrophically entombed the flora and vegetation developing in the surrounding region, facilitating their preservation as fossils. Currently, the study of such examples is focused on the continental Palaeozoic and Mesozoic record. However, on oceanic islands, volcanic in nature, sub-Plinian to Plinian eruptions occurred, although their palaeobotanical potential has been less studied. This is the case of Tenerife Island (Canary archipelago), where plant fossils associated with pyroclastic deposits from the Las Cañadas volcano ( ca. 3.5 Ma-present) are known, but never studied in detail. These deposits occur abundantly in the south face of the island, where currently, under the influence of a xeric Mediterranean climate, succulent Euphorbia scrubs and shrublands grow. Fossils associated with these vegetation types are unknown for the Canary Islands. Here we report the first evidence of in situ Euphorbia canariensis L. stem fossils preserved within pyroclastic deposits from the 312 kyr Diego Hernández Formation (Las Cañadas Volcano), in the southeast of Tenerife Island. The taphonomy indicates that the plants were covered by a wet and plastic ash-fall and buried in situ by pumice-fall deposits. Later decay led to the preservation of the stems as external moulds. These can be assigned to E. canariensis due to stem morphology, the presence of cyathia, and by cuticular characters. The present work highlights the unique volcanic taphonomy and the rare preservation of succulent plants as in situ fossils, pointing to its importance to understand past lowland xeric ecosystems of the Canary archipelago.