A new gnetalean macrofossil from the Lower Cretaceous of the Laiyang Basin, eastern China

Macrofossils of Gnetales have revealed high morphological diversity in the Mesozoic, and most of them have been found in northeastern China. However, this diversity almost entirely disappeared in the Late Cretaceous causing a bottleneck effect in Gnetales with extraordinarily low levels of genetic and structural diversity. Here, we describe a new species, Laiyangia compacta gen. et sp. nov., with unusual female spikes from the Early Cretaceous of the Laiyang Formation in Shandong Province, eastern China. This species is the first record of a gnetophytes from the Laiyang Formation. It is similar to Liaoningia, Chengia and Liaoxia in possessing compact female spikes with no observable nodes and internodes and multiple pairs of fertile bracts, but differs from all known species by its more compact female spikes and plumper seeds. This new species expands our knowledge about the diversity of early gnetophytes in the Lower Cretaceous, and we determined the phylogenetic relationship of L. compacta within Gnetales based on the maximum parsimony analysis. Moreover, our new macrofossil displaying additional morphological and epidermal microstructural characters provides further evidence of the early evolution of female reproductive organs of gnetophytes and the palaeoclimate of the Laiyang area in the Early Cretaceous. © 2024 Kunming Institute of Botany, Chinese Academy of Sciences