Fossil woods preserved in deposits through the process of permineralization play a crucial role in reconstructing the floristics aspects of ancient forest ecosystems and climatic conditions in deep time. Fossil woods have been widely discovered in terrestrial ecosystems from the dinosaurs ages in the Jurassic and Cretaceous. In China, the fossil woods are mainly documented in the northern China region; however, the records in southern China are relatively poor.

Recently, a new extinct species of conifer wood dated over 100 million years, i.e. Brachyoxylon zhoui was reported by a research team lead by Prof. WANG Yongdong at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) and Dr. JIANG Zikun at the Chinese Academy of Geological Sciences, in conjunction with the other researchers at the Zhejiang Museum of Natural History, Shenyang Normal University, and University of Bonn in Germany. This finding was recently published in the international journal Historical Biology.

The fossil wood specimen was found in the Early Cretaceous Guantou Formation (about 110 Ma) in Yongkang City of Zhejiang Province, which is anatomically different from any reported fossil woods in Zhejiang. Based on comparisons between the present fossil wood material and other relative fossil woods worldwide, a new species of the morphogenus Brachyoxylon, i.e. Brachyoxylon zhoui was established by the research team. The specific name zhoui is dedicated to Prof. ZHOU Zhiyan from Nanjing for his contributions to Palaeonbotany.

The terrestrial sediments, largely deposited during the Early Cretaceous in Zhejiang, contain vertebrate fossils, such as dinosaur bones and eggs, and additionally yield abundant fossil woods. The new fossil wood material is silicified and part of the secondary xylem of the tree. The new species is characterized by distinct growth rings, a mixed type of radial tracheary pitting, araucarioid cross-field pitting, high uniseriate rays, and traumatic resin canals. The quantitative analysis of the growth ring was carried out by researchers, indicating that the forest composition was evergreen with a Leaf Retention Time (LRT) of 3–15 years. Combined with the analysis of sedimentology, palynology and paleosols, researchers assume that the Zhejiang region was dominated by a subtropical to tropical and relatively semiarid climate during the Early Cretaceous.

The discovery of Brachyoxylon zhoui not only enriches the understanding of the fossil forest composition and paleoclimate but also provides the essential evidence to reconstruct the paleohabitats of dinosaurs in the Early Cretaceous of Zhejiang Province.

The study was co-corresponded by Dr. JIANG Zikun at the Chinese Academy of Geological Sciences and Prof. WANG Yongdong at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, other co-authors include Dr. WU Hao at the Zhejiang Museum of Natural History, Associate Professor TIAN Ning at the Shenyang Normal University, and Ph.D. candidate XIE Aowei at the University of Bonn in Germany. 

This research was co-supported by the National Natural Sciences Foundation of China, the Strategic Priority Program (B) of CAS, the State Key Program for Basic Research & Development of Ministry of Science & Technology of China and the State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS).

Reference: Jiang Zikun*, Hao Wu, Ning Tian, Yongdong Wang*, Aowei Xie, 2020. A New Species of Conifer Wood Brachyoxylon from South China and its Palaeoclimatic Implications. Historical Biology, https://doi.org/10.1080/08912963.2020.1755282

The anatomical structures of growth rings, radial tracheary pitting in fossil conifer wood Brachyoxylon zhoui from the Early Cretaceous in Zhejiang Province of China

The anatomical structures of cross-field pitting and xylem rays in fossil conifer wood Brachyoxylon zhoui from the Early Cretaceous in Zhejiang Province of China

The quantitative analysis of the growth ring and paleoclimate of fossil conifer wood Brachyoxylon zhoui from the Early Cretaceous in Zhejiang Province of China