Grenana seed-fern (Grenana)

Grenana: Middle Jurassic Ginkgophyte Genus from Central Asia

Fossil deposits in Central Asia have yielded remains of Grenana, a prehistoric member of the Ginkgoaceae family. This genus lived during the Middle Jurassic period, showcasing reproductive traits that connect it to other early ginkgophytes.

The genus is currently monotypic, represented solely by the type species Grenana angrenica, which was described in 1990 by the paleobotanist Samylina.

Taxonomy

Morphology

The architectural characteristics of this genus highlight its affinity with the Ginkgoales, though its vegetative remains were once misidentified. Its structures display a mix of ancestral gymnosperm features.

  • Seed Organs: The seed-bearing structures show a strong resemblance to those of Nehvizdyella, featuring seeds enclosed within a large, protective cupula.
  • Seed Similarity: Aside from the enclosing cupula, the individual seeds themselves closely resemble those of the modern Ginkgo genus.
  • Foliage: The leaves of this plant are petiole-less and dichotomously branched, aligning with the Baiera or Sphenobaiera morphotypes.

Interesting facts

During their initial discovery, the fossilized leaves of this genus were misclassified. Paleontologists originally assigned them to the pteridosperms (seed ferns) before recognizing their true affinity with the Ginkgoales.

Its discovery near Angren in Uzbekistan has provided significant data regarding the paleogeographic distribution of ginkgophytes across Central Asia during the warm, humid Jurassic period.

Geography of distribution

  • Uzbekistan

Sources

  • Samylina, V. A. (1990). Grenana - a new genus of Ginkgoales from the Middle Jurassic of Angren.
  • Zhou, Z. (2009). An overview of fossil Ginkgoales. Palaeoworld, 18(1), 1-22.
  • Taylor, T. N., Taylor, E. L., & Krings, M. (2009). Paleobotany: The Biology and Evolution of Fossil Plants. Academic Press.

Technical Information

External Databases: GBIF