Diversity of Early Permian ginkgophyte-like foliage from the Lodève basin, France
Résumé
In 1875, Saporta described seed-bearing organs from Autunian (earliest Permian) deposits of Lodève, France, that he assigned to a new genus and species, Trichopitys heteromorpha. Following Florin’s work (1949), this genus has been regarded by most authors as the archetype of ginkgoalean ovulate structures and one of the oldest bona fide evidence of ginkgophytes in the fossil record. While there is a general consensus that ginkgophytes originated in the Late Paleozoic, the exact timing of this apparition is uncertain. Most of our knowledge comes from compression/impressions of leaves reported in Permian -and even Pennsylvanian- deposits from all around the world. However in the absence of associated reproductive structures, the affinities of these ginkgophyte –like leaves remain uncertain and the long and complex taxonomic history of most taxa further clouds the situation. Several morphogenera have been reported in the early Permian, including four (Baiera, Ginkgophyllum, Ginkgoites, and Sphenobaiera) that were reported from the Lodève Basin by Doubinger (1956). While there are undeniable morphological overlaps between some of these genera, it makes no doubt that several distinct morphotypes of ginkgophyte-like leaves were already present by the Early Permian. In this study, we use collection material dating back to Saporta’s time and more recently discovered specimens to synthetize and discuss the diversity of ginkgophyte foliage in the Early Permian deposits of the Lodève Basin that have yielded Trichopitys. Several different morphotypes are recognized (Fig. 1) and compared with previously described taxa. Some specimens correspond to taxa previously reported in the basin, such as Ginkgophyllum or Baiera (e.g., Fig.1. A-C), while other are more comparable to Esterella, a genus previously reported in the Late Permian of France and Germany (Boersma & Visscher, 1969; Bauer et al., 2013; e.g., Fig. 1 D). We show that the diversity of ginkgophyte-like foliage was indeed already high in the Early Permian, which supports the idea that gingkophyte diversification happened earlier than can be detected by reproductive structures only.
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REFERENCES:
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