Mastixioid fruits (Cornales) from the early Eocene London Clay Flora: morphology, anatomy and nomenclatural revision

Following on the seminal works of Reid and Chandler in 1933 and Chandler in 1961, morphology and anatomy of fossil mastixioid fruits from the early Eocene London Clay of southern England were reanalyzed with the benefit of new methods in comparison with extant genera of Mastixiaceae and with other fossil representatives from Europe and North America. The species named Mastixia cantiensis E.Reid et M.Chandler was based on a heterogeneous assemblage of specimens, all representing Mastixiaceae, some of which truly represent Mastixia whilst others correspond to Diplopanax and Mastixiopsis The holotype of M. cantiensis E.Reid et M.Chandler corresponds to extant Diplopanax rather than Mastixia. Therefore, this species is moved out of Mastixia and is treated as Diplopanax cacaoides (Zenker) comb. nov. Nine species of mastixioid fruits are currently recognized in the London Clay flora: Mastixia parva E.Reid et M.Chandler, M. cf. oregonensis (R.A.Scott) Tiffney et Haggard, Diplopanax cacaoides, Tectocarya grandis (E.Reid et M.Chandler) comb. nov., Mastixiopsis nyssoides Kirchh., Exbeckettia mastixioides (E.Reid et M.Chandler) gen. et comb. nov., Lanfrancia subglobosa E.Reid et M.Chandler, Portnallia bognorensis M.Chandler, and Langtonia bisulcata E.Reid et M.Chandler. These include the oldest known representatives of the genera Diplopanax, Tectocarya and Mastixiopsis and contribute to our understanding of the former morphological diversity and palaeobiogeography of the Mastixiaceae.