A new species of Pararaucaria from the Lower Cretaceous of Shandong province (Eastern China): Insights into the evolution of the Cheirolepidiaceae cone

Abstract

Pararaucaria, a genus of the extinct conifer family Cheirolepidiaceae, was previously identified from permineralized fossils. This genus reflects important changes in the phylogeny and evolutionary biology of Cheirolepidiaceae. We describe a new species of Pararaucaria (Pararaucaria laiyangensis) from the Lower Cretaceous of the Laiyang Formation in Shandong Province, eastern China using standard paleobotanical descriptions and micro-computed tomography techniques. P. laiyangensis consists of small seed cones with helically arranged bract-scale complexes, isolated ovuliferous scales, and associated scale-leaf foliage with obvious cuticle structures. Bract-scale complexes consist of separated bracts and ovuliferous scales with one seed and three distal lobes. Cuticles consist of haplocheilic and monocyclic stomata arranged in longitudinal rows all over the surface. We assigned the phylogenetic relationship of P. laiyangensis within Cheirolepidiaceae based on the parsimony analyses, and highlight the homology of ovuliferous scales in Pararaucaria and Araucaria according to the comparison with ovuliferous scale structures of all major conifers. Moreover, this species increases our understanding of the dominant tree element of the Laiyang fossil forest, providing the first evidence for ovulate cheirolepidiaceous cones in Asia based on the global distribution of Cheirolepidiaceae reproductive organs.