Abstract
BackgroundFossil evidence of ginkgophyte ontogeny is exceedingly rare. Early development in the extant Ginkgo biloba is characterized by a series of distinct ontogenetic stages. Fossils providing insights into the early ontogeny of ancient ginkgophytes may be significant in assessing the degree of relatedness between fossil ginkgophytes and G. biloba.ResultsAn assemblage of seedlings from the early Middle Triassic of France is assigned to the ginkgophytes based on leaf morphology. The specimens represent an ontogenetic sequence consisting of four stages: (I) formation of the cotyledons in the seed and germination; (II) development of primary leaves and taproot; (III) thickening of the taproot and appearance of secondary roots; and (IV) development of the first differentiated leaves and absence of the seed remnants.ConclusionsThe fossil seedlings provide a rare opportunity to examine the early ontogeny of a Triassic ginkgophyte. Germination and seedling development in the fossil are nearly identical to that of the extant gymnosperm G. biloba. We hypothesize that the fossil may be closely related biologically to G. biloba, and that certain developmental processes in seedling development were in place by the Middle Triassic.
Highlights
Fossil evidence of ginkgophyte ontogeny is exceedingly rare
Compressed seedlings attributed to the herbaceous conifer Aethophyllum stipulare have been reported from the Middle Triassic Voltzia Sandstone of France [5], and a conifer embryo with cotyledons has been described from the Upper Pennsylvanian or Lower Permian of North America [6]
We describe an assemblage of 20 compression specimens of seedlings from a single bedding plane in the Voltzia Sandstone
Summary
Fossil evidence of ginkgophyte ontogeny is exceedingly rare. Development in the extant Ginkgo biloba is characterized by a series of distinct ontogenetic stages. Fossil evidence of gymnosperm ontogeny is exceedingly rare and mostly limited to isolated specimens of embryos and/or seedlings [1]. Compressed seedlings attributed to the herbaceous conifer Aethophyllum stipulare have been reported from the Middle Triassic Voltzia Sandstone of France [5], and a conifer embryo with cotyledons has been described from the Upper Pennsylvanian or Lower Permian of North America [6]. The early ontogenetic development of fossil representatives of the ginkgophytes has remained unknown due to a lack of fossils that could be used to reconstruct this process
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