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.

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