New record of the conifer wood taxon Brachyoxylon from the Middle Jurassic in southwestern China, and a global survey of paleobiogeography of the Mesozoic Brachyoxylon occurrences

Abstract

Fossil wood is one of the most important proxies for terrestrial vegetation composition and continental paleogeographical reconstruction in Earth's history. The conifer wood Brachyoxylon is commonly found in Mesozoic deposits in Europe, Africa, South America, and Antarctica with more than one hundred known occurrences to date. However, only few occurrences (∼5%) are so far documented in China of East Asia. Here, we describe a fossil wood specimen from the Middle Jurassic Upper Shaximiao Formation at Yongxin of Chongqing City in southeastern Sichuan Basin, China, exhibiting typical Brachyoxylon anatomy with mixed radial tracheid pitting and araucarioid cross-field pitting. According to the characters of radial tracheid pitting, cross-field pitting, and ray height, the wood is recognized as Brachyoxylon trautii (Barale) Philippe 1995. To better understand the paleobiogeography of the Mesozoic Brachyoxylon, a global survey of its occurrences is performed, which shows that Brachyoxylon was globally expanding over time with the widest geographic distribution in the Cretaceous.