Jurassic Ferns from the Girón Group: A Window into Ancient Tropical Ecosystems

A new study published in the Journal of South American Earth Sciences opens a small window on the flora and environmental conditions of tropical South America during the Late Jurassic. 

The paper, "Jurassic fern Piazopteris from the Girón Group, Colombia: A taxonomic and paleoenvironmental evaluation," presents the discovery and analysis of six fossil fern specimens from the Eastern Cordillera of Colombia, helping expand a bit of knowledge of Jurassic plant life in the paleo-Caribbean region.

The fossils were collected from the carbonaceous mudstones of La Honda Creek, part of the Girón Group—an important but underexplored sedimentary unit that preserves traces of Mesozoic terrestrial ecosystems. The ferns are tentatively identified as Piazopteris cf. branneri, a member of the now-extinct genus of the Matoniaceae. Piazopteris once thrived in humid, equatorial climates.

What makes this study particularly compelling is its multidisciplinary approach. Using thin-section petrography, scanning electron microscopy (SEM), and carbon geochemistry—including total organic carbon (TOC) and stable isotope (δ¹³Corg) analyses—the researchers aproximated the depositional environment and climate context of these fossils. The results point to a low-energy, swamp-like setting with significant organic accumulation, likely influenced by a humid, tropical to subtropical climate. The geochemical data not only support this interpretation but also provide a valuable window into the carbon cycling and preservation conditions of Jurassic terrestrial environments.

The genus Piazopteris is a biostratigraphically and paleoecologically relevant genus, typically associated with Jurassic-Cretaceous floras of Gondwanan affinity. The occurrence of Piazopteris cf. branneri in Colombia contributes to a growing record of Jurassic ferns in South America and provides important taxonomic refinements for this group, which has often been misidentified or found poorly preserved.

Importantly, this work also underscores the scientific potential of the Girón Group as a paleobotanical archive. While the Girón Group has been recognized for its sedimentological and tectonic significance, its paleontological potential remains vastly underutilized. This new contribution highlights the need for further research, particularly stratigraphic refinement, paleobotanical and geochemical work in this region.

This study was carried out by a multidisciplinary team of geologists and paleontologists from several institutions in Colombia and abroad, including the Universidad Industrial de Santander (UIS), Florida International University (FIU), and research institutes focused on stratigraphy and paleontology. The collaboration brought together the fields of sedimentology, paleobotany, geochemistry, and microscopy to advance understanding of Jurassic floras in tropical settings. 

Special thanks go to all who helped make this discovery and research possible.

Citation:

Torres-Parada, J.M., Orihuela, J., Alarcón Gómez, C.M., Diaz Villamizar, J.S., Gómez-Coronado, J.S., Márquez-Prada, J.J., Lizarazo-Pabón, J.A., Patarroyo, G. (2025). Jurassic fern Piazopteris from the Girón Group, Colombia: A taxonomic and paleoenvironmental evaluation. Journal of South American Earth Sciences, 158, 105488. https://doi.org/10.1016/j.jsames.2025.105488

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