Plant remains from the Middle–Late Jurassic Daohugou site of the Yanliao Biota in Inner Mongolia, China

Abstract

ABSTRACT. A late Middle-early Late Jurassic fossil plant assemblage recently excavated from two CallovianOxfordian sites in the vicinity of the Daohugou fossil locality in eastern Inner Mongolia, China, was analysed in detail. The Daohugou fossil assemblage is part of the Callovian-Kimmeridgian Yanliao Biota of north-eastern China. Most major plant groups thriving at that time could be recognized. These include ferns, caytonialeans, bennettites, ginkgophytes, czekanowskialeans and conifers. All fossils were identified and compared with species from adjacent coeval floras. Considering additional material from three collections housed at major palaeontological institutions in Beijing, Nanjing and Pingyi, and a recent account in a comprehensive book on the Daohugou Biota, the diversity of the assemblage is completed by algae, mosses, lycophytes, sphenophytes and putative cycads. The assemblage is dominated by tall-growing gymnosperms such as ginkgophytes, czekanowskialeans and bennettites, while seed ferns, ferns and other water-or moisture-bound groups such as algae, mosses, sphenophytes and lycophytes are represented by only very few fragmentary remains. The floral composition underlines the Callovian-Kimmeridgian age of the Yanliao Biota. The Daohugou/Yanliao flora is a typical member of the Middle to Late Jurassic Coniopteris-Phoenicopsis assemblage of north-eastern China, differing from the Early Cretaceous Jehol flora. Both floras probably belong to the same cycle of volcanism and sedimentation, although the Daohugou Bed is older than the Yixian Formation. The Yanliao fossil assemblage is placed in a larger palaeo-phytogeographical context and its relationships with Middle-Late Jurassic floras from north-eastern China, north-eastern and eastern Siberia and Japan are evaluated.

How deep is the conflict between molecular and fossil evidence on the age of angiosperms?

“…A general problem is that the proposed Jurassic angiosperms known as isolated reproductive structures (Solaranthus, Euanthus, Nanjinganthus, Xingxueanthus) occur in compression floras that are rich in typical Jurassic ferns, ginkgophytes, cycadophytes, and conifers (e.g. Na et al, 2017;Pott & Jiang, 2017;Fu et al, 2018) but contain no leaves with distinctive angiosperm apomorphies (several orders of reticulate venation, etc. ), whereas those known as nearly whole plants (Schmeissneria, Juraherba, Yuhania) have leaves with no angiosperm features.…”

Palaeoenvironmental reconstruction and biostratinomic analysis of the Jurassic Yanliao Lagerstätte in northeastern China

“…The plants include ferns, caytonialeans, bennettites, ginkgophytes, czekanowskialeans and conifers. Among these, tall-growing gymnosperms are dominant, preserving entire or large fragments of leaves and organs, while water-or moisturebound groups such as ferns are represented by only rare fragmentary remains (Pott and Jiang, 2017).…”

“…Indeed, the Daohugou fossils probably drifted far offshore (Fig. 7B), as indicated by the accompanying plant fossil assemblage including mostly large land plants with minor low-growing waterrelated plants (Pott and Jiang, 2017). The abundance and high fidelity of preservation of insects, however, probably reflects minimal floatation prior to burial.…”

“…The presence of highlands surrounding the lake(s) is supported by extensive fan-delta deposits and the preservation of alpine insects and upland plants in the lacustrine deposits (Liu et al, 2010;Na et al, 2015;Na et al, 2017;Pott and Jiang, 2017). The relatively high abundance of land plant debris in pyroclastic flow deposits and the paucity of epiclasts derived from weathering suggest that the region adjacent to the lake(s) was well vegetated.…”

“…The Middle to Late Jurassic lacustrine deposits in the region encompassing the confluence of Inner Mongolia, Hebei and Liaoning provinces, northeastern China, preserve numerous exceptionally preserved land and aquatic animal fossils (Fig. 1), including various plants (algae, mosses, lycophytes, sphenophytes, ferns, seed ferns, cycadophytes, ginkgophytes and conifers), invertebrates (bivalves, anostracans, spinicaudatans, arachnids and insects) and vertebrates (fish, salamanders, anurans, squamates, pterosaurs, dinosaurs and mammaliaforms) (Huang et al, 2006;Sullivan et al, 2014;Pott and Jiang, 2017), yielding taxa that represent the earliest examples of their respective clades or reveal key evolutionary transitions (e.g. Gao and Shubin, 2003;Ji et al, 2006;Luo et al, 2007;Xu et al, 2009;Lü et al, 2010;Luo et al, 2011;Xu et al, 2011;Huang et al, 2012;Bi et al, 2014;Cai et al, 2014;Xu et al, 2015).…”