Plant mobility in the Mesozoic: Disseminule dispersal strategies of Chinese and Australian Middle Jurassic to Early Cretaceous plants
Abstract Four upper Middle Jurassic to Lower Cretaceous lacustrine Lagerstatten in China and Australia (the Daohugou, Talbragar, Jehol, and Koonwarra biotas) offer glimpses into the representation of plant disseminule strategies during that phase of Earth history in which flowering plants, birds, mammals, and modern insect faunas began to diversify. No seed or foliage species is shared between the Northern and Southern Hemisphere fossil sites and only a few species are shared between the Jurassic and Cretaceous assemblages in the respective regions. Free-sporing plants, including a broad range of bryophytes, are major components of the studied assemblages and attest to similar moist growth habitats adjacent to all four preservational sites. Both simple unadorned seeds and winged seeds constitute significant proportions of the disseminule diversity in each assemblage. Anemochory, evidenced by the development of seed wings or a pappus, remained a key seed dispersal strategy through the studied interval. Despite the rise of feathered birds and fur-covered mammals, evidence for epizoochory is minimal in the studied assemblages. Those Early Cretaceous seeds or detached reproductive structures bearing spines were probably adapted for anchoring to aquatic debris or to soft lacustrine substrates. Several relatively featureless seeds in all assemblages were potentially adapted to barochory or to endozoochory—the latter evidenced especially by the presence of smooth seeds in vertebrate gut contents and regurgitant or coprolitic masses. Hydrochory is inferred for several aquatic plants that notably bear small featureless seeds, particularly aggregated into detachable pods.