Occurrence of the earliest gigantopterid from the basal Permian of the North China Block and its bearing on evolution

Abstract

Gigantopterids are a morphological group consisting of a number of enigmatic fossil plants with angiosperm‐like leaves and reticulate venation that are of uncertain systematic affinity. Gigantopterid plants were abundant and a characteristic floral element in the Late Palaeozoic Cathaysian floras. However, in China, their oldest occurrence was much later than that in North America (Artinskian) and Indonesia (Asselian to Sakmarian). Here, we document the gigantopterid Gigantonoclea cf. mira from basal Permian (Asselian) strata in the North China Block that represents the oldest unequivocal evidence for the gigantopterids. The foliage is characterized by complex venation composed of four orders, small isodiametric meshes, and intercalary subsidiary veins arising directly from the rachis, being a distinctive morphological type of leaf venation. In addition, a nonmarginal feeding trace is detected on the lamina, extending the earliest record of plant–animal interaction between gigantopterid plants and arthropods to the earliest Permian. Our new observations show that the venation characters of Gigantonoclea mira and Gigantonoclea cf. mira more closely resemble Gigantopteris dictyophylloides than other members of gigantopterids including the evolutionary Callipteridium sequence to which it was previously assigned.

Influence of temporally varying weatherability on CO<sub>2</sub>–climate coupling and ecosystem change in the late Paleozoic

“…Notably, the CO 2 decline across the Carboniferous-Permian boundary into the 10-Myr nadir and early Permian peak in O 2 :CO 2 also corresponds to the evolution and radiation of glossopterids and gigantopterids (McLoughlin, 2011;Zhou et al, 2017), with increasing vein density in the former (Fig. 3a-c; Srivastava, (1991)).…”

A new gigantopterid genus from the late Permian of the Daha Coalfield, Tibetan Plateau and its implication on plant-insect interactions

“…For example, recent research documenting the genus Gigantonoclea in the earliest Permian Asselian Stage of North China contradicts Asama's growth retardation theory in which this seemingly advanced genus occurs in the fossil record significantly earlier than its suggested ancestors (Zhou et al 2018).…”

“…Early accounts placed all gigantopterids in the genus Gigantopteris, but Koidzumi (1934) was first to recognize their morphological differences and re-classified them into five subfamilies and eight genera (Koidzumi 1934(Koidzumi , 1936. Up to now, over 20 genera have been established within the gigantopterids (see Zhou et al 2018 for recent review).…”

“…Although some accounts of gigantopterid plants include details of epidermal (Wang 1999;Yao and Liu 2004;DiMichele et al 2011), anatomical (e.g., Mamay et al 1988;Li et al 1996;Taylor 1998, 1999) and alleged reproductive features (e.g., Li and Yao 1983b;Zhu and Zhang 1995;Wang 1999), their systematic affinity remains uncertain. Current evidence suggests that gigantopterids are not a monophyletic group but share convergent traits of megaphyllous leaves with multi-ordered net venation (Glasspool et al 2004a(Glasspool et al , 2004bDiMichele et al 2011;Zhou et al 2018). In terms of their morphology, several distinct evolutionary pathways have been proposed within gigantoperids involving a theory termed "Growth Retardation" in which gigantopterid leaves were assumed to have evolved by the fusion of segments of more simple leaves into larger leaves with more complex venation patterns (Asama 1959;Shen et al 1977;Booi et al 2009).…”

“…From that region abundant well-preserved leaves were systematically described and classified into 36 species from 12 genera based on their leaf architecture and venation patterns. For instance, in the simple-meshed leaves of Gigantonoclea (Koidzumi), those with fern-like compound architecture with apically fused laminae which fit the original diagnosis of the genus were maintained in Gigantonoclea sensu-stricto, whereas those with petiolate compound architecture with apically separated leaflets or simple leaves and axillary buds present were transferred to Pinnagigantonoclea Yang and Monogigantonoclea Yang respectively (Yang 2006;Zhou et al 2018). Similar categories have also been applied in the double-meshed leaves of Gigantopteris where those with petiolate compound architecture and an apical leaflet were transferred to Pinnagigantopteris Yang, while those with simple leaves and axillary buds present were transferred to Monogigantopteris Yang (Yang 2006).…”