A new species of Elatides from the Lower Cretaceous in Shandong province, Eastern China and its geographic significance

Abstract

Elatides, an ancient extinct conifer, is of great significance for studying the composition of forest vegetation in the Northern Hemisphere during the Mesozoic. A new Elatides species, Elatides laiyangensis sp. nov., has been described and diagnosed from the Lower Cretaceous Laiyang Formation in Shandong Province, China. The details of the gross morphology and cuticular structure of the new species have been studied. The significant characters of the studied fossils can be concluded as follows: the seed cones are ovate or round, and the middle part of the cone is the widest. It tapers slightly near the apex; the bract–scale complexes are numerous, broad–ovate or triangular–ovate, helically and imbricately arranged on the cone axis and compactly in each other, with an acuminate and slightly curved inward apex; the epidermal cells on the apex and middle part of bracts are irregular polygonal, and long–rectangular or long–rectangular on the side edge and basal; and the stomata complexes are predominantly on the apex and middle part of the adaxial surface. These features are much similar to those of the extant Cunninghamia, which provides further support for a phylogenetic relationship between Elatides and Cunninghamia. Since the morphological (macrostructure and microstructure) features of this species differ from any known species in the fossil records, it can be considered as a new species of Elatides. Associated leafy branches are also comparable to those of Cunninghamia lanceolata in shape and cuticular structure. The geographical distribution of Elatides through time is closely related to the prosperity-decline of the genus, geological events in Mesozoic and the trends of global paleoenvironmental change. Therefore, it can be inferred that this genus may possess high sensitivity to climate change, especially to temperature. Furthermore, the occurrences of Elatides seed cones and foliage shoots from the Laiyang Basin provide new information on the geographic distribution of Elatides in China, which indicates that Shandong should be the adaptive way through which the genus was transported from Hebei (Northern China) to Zhejiang and Fujian (Southern China).