The Early Cretaceous Apple Bay flora of Vancouver Island: a hotspot of fossil bryophyte diversity

摘要

The pre-Cenozoic bryophyte fossil record is significantly sparser than that of vascular plants or Cenozoic bryophytes. This situation has been traditionally attributed to a hypothesized low preservation potential of the plants. However, instances of excellent pre-Cenozoic bryophyte preservation and the results of experiments simulating fossilization contradict this traditional interpretation, suggesting that bryophytes have good preservation potential. Studies of an anatomically preserved Early Cretaceous (Valanginian) plant fossil assemblage on Vancouver Island (British Columbia), at Apple Bay, focusing on the cryptogamic flora, have revealed an abundant bryophyte component. The Apple Bay flora hosts one of the most diverse bryophyte assemblages worldwide, with at least nine distinct moss types (polytrichaceous, leucobryaceous, tricostate), one complex thalloid liverwort, and two other thalloid plants (representing bryophyte or pteridophyte gametophytes), which contribute a significant fraction of biodiversity to the pre-Cenozoic fossil record of bryophytes. These results (i) corroborate previous observations and studies, indicating that the preservation potential of bryophytes is much better than traditionally thought; (ii) indicate that the bryophyte fossil record is incompletely explored and many more bryophyte fossils are hidden in the rock record, awaiting discovery; and (iii) suggest that the paucity of the pre-Cenozoic bryophyte fossil record is primarily a reflection of inadequate paleobryological capacity.