A new extinct conifer Brachyoxylon from the Middle Jurassic in southern China: Wood anatomy, leaf phenology and paleoclimate

Abstract

The Jurassic System in the Sichuan Basin of eastern Asia is represented by the extensive development of massive thick red beds, mainly composed of purplish-red sandstones and mudstones. Abundant invertebrate and vertebrate fossils have been recovered from these Jurassic red beds. However, fossil woods are much less documented. Here, we describe fossil woods from the Middle Jurassic Shaximiao Formation at Qijiang of Chongqing City in southeastern Sichuan Basin, China, obtaining typical Brachyoxylon anatomy with mixed radial tracheid pitting and araucarioid cross-field pitting. Owing to a novel combination of radial tracheid pitting, cross-field pitting and ray height, a new species, Brachyoxylon qijiangense Xie, Wang et Tian sp. nov. is recognized here. Based on the tree mean sensitivity and leaf retention time analysis, along with the comparison with other invertebrate and leaf fossils in the Shaximiao Formation, the new fossil woods bearing true growth rings with abundant, well-formed earlywood and extremely narrow latewood indicates that B. qijiangense sp. nov. was an evergreen tree growing in a warm and humid climate with mild seasonality during the Middle Jurassic in Qijiang, probably in a flooding-disturbed, streamside condition.