BENNETTITALES FROM THE GRISETHORPE BED (MIDDLE JURASSIC) AT CAYTON BAY, YORKSHIRE, UK

Middle Jurassic fossil plants from the Grisethorpe Bed at Cayton Bay and Grisethorpe Bay, Yorkshire, UK, are preserved in a soft claystone, and plant mesofossils recovered by sieving reveal excellent details of external structure. Studies of these mesofossils complement previous work on macrofossils from the Grisethorpe Bed and allow the plant fossils in this classic flora to be studied in a similar way to those preserved in Cretaceous mesofloras. Bennettitales, a key group in discussions of how angiosperms may be related to other seed plants, are especially well represented among mesofossils from the Grisethorpe Bed. Abundant bennettitalean leaves, scale leaves, and fragments of pollen and ovulate organs provide new information on these extinct plants. In particular, a specimen of Williamsoniella coronata (presumed aborted) shows only weak differentiation between interseminal scales and ovules and provides further evidence of homology between these structures.