Sprecher
Beschreibung
Highly allochthonous plant megafossil assemblages from Bearreraig, Skye, offer a rare opportunity to study the well preserved anatomy of several Middle Jurassic tracheophytes. Deposited in fully marine stenohaline conditions offshore from multiple river discharges, the 14 plant-bearing horizons spanemphasized text ~110 m (5 MYr) of early Aalenian to early Bajocian strata. They have yielded ~16 disarticulated organ-species that represent a minimum of nine whole-plant species: one equisetalean (one pyritised axis), four filicalean ferns (frequent fusainised pinnae, occasional rachises), one cycad (rare permineralised leaves, seeds), one bennettite (rare permineralised leaves), and at least two conifers (common permineralised leafy shoots, insect-bored woody axes, wood fragments; rare cones). Calcitic nodules enclosing the plant megafossils also contain diverse assemblages of well preserved miospores (dominantly bisaccates), and representatives of many major groups of contemporaneous marine biota, collectively establishing Bearreraig as the reserve Aalenian–Bajocian stratotype. Detailed palaeobotanical descriptions of permineralised organs have thus far encompassed the two cycadophyte leaves (Nilssonia tenuinervis, Otozamites mortonii) and two coniferous ovulate cones belonging to new genera of Cupressaceae that were subjected to XRT examination. Scitistrobus duncaanensis is assigned to subfamily Cunninghamioideae, whereas Pyrostrobus gerontostorros – the subject of ongoing research – is tentatively assigned as a stem-group to the more derived subfamily Sequoioideae, constituting by far its earliest known member. Both cones exhibit charred exteriors and the accompanying fern fossils are reliably fusainised, suggesting that periodic wildfires caused low-temperature crown-fires in an open coniferous forest while wholly consuming the fern-dominated understorey.