Early Oligocene Calocedrus (Cupressaceae) from the Maoming Basin, South China, and its paleogeographic and paleoclimatic implications

摘要

The genus Calocedrus Kurz is characterized by flattened branches covered with decussate and dimorphic leaves.In this study,we describe fossil foliage of Calocedrus discovered in the Shangcun Formation (early Oligocene) of the Maoming Basin,South China.The fossils have wedge-shaped branchlet segments and scale-like strongly dimorphic leaves,similar to the fossil species Calocedrus lantenoisi (Laurent) Tao.There have been no detailed studies of the morphological features and cuticle structures of C.lantenoisi.Therefore,a newly emended diagnosis of the species C.lantenoisi is given based on a detailed study of leaf morphology and cuticular characters exhibited by the Maoming fossils.This is one of the earliest fossil records of Calocedrus in the world,providing additional evidence for the early biogeographic history of this genus and supporting the inference that eastern Asian Calocedrus is primitive among all the living species.The extant species of Calocedrus are mainly distributed in mountainous regions.On the basis of the "nearest living relative" analysis,we propose that the Maoming Basin was adjacent to a mountainous region during the early Oligocene.