A new Late Devonian plant assemblage in West Junggar, Xinjiang, China and its floral evolution during the Devonian

Abstract

Mid to Late Devonian witnessed the emergence of the first forest and global flora prosperity on the Earth. West Junggar, a distinct sub-terrain of the Kazakhstan Paleoblock, in which Middle to Upper Devonian plant fossil-rich deposits are exposed, that significantly contribute to our understanding of Devonian plant diversity and flora evolution. In this study, we report a new plant assemblage from the Hongguleleng Formation in the Kekesayi and western Yangzhuang sections of West Junggar, Xinjiang, China. The dominant palynomorphs in this assemblage are retusoid and laevigate trilete spores with occasional scolecodonts. Macroplants of the assemblage consist of tree-like and herbaceous lycopsids. At least two floral turnovers were documented in West Junggar during the Devonian. The first one occurred at the end of the Givetian Age and saw the transformation of the Hujiersite Flora dominated of herbaceous lycopsids, turning into the flora with arborescent plants as typical of the Zhulumute Flora. The second turnover might occur near the Frasnian-Famennian boundary and saw the forest of the Zhulumute Flora shifting into the Hongguleleng Flora with more widely-distributed members.