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

Images created with AI (ChatGPT Image creator, 2025). 

Ancient Sand Dollars Reveal a Lost Caribbean Ecosystem: New Findings from South-Central Cuba

The fossil record offers glimpses into ancient worlds, and a new study on Clypeaster echinoids from Cuba’s Damují Formation provides valuable insights into the Caribbean’s past. These fossils, dating from the Late Eocene to Early Oligocene, represent some of the earliest known occurrences of this genus in the region.

The research, conducted in Rodas, south-central Cuba, extends the known temporal and geographical range of Clypeaster, a genus of sand dollars that still thrives in tropical and subtropical oceans today. While previous studies focused on Oligocene and Miocene specimens, these newly examined fossils fill a gap in our understanding of how echinoids evolved and dispersed during a critical period of climatic transition—the Eocene-Oligocene boundary.

The geological context of the Damují Formation suggests that Clypeaster lived in a diverse marine environment, alongside large foraminifera, corals, and small fish. The presence of these fossils indicates that warm, shallow-water reef systems persisted in the Caribbean despite global cooling trends at the time. This challenges previous assumptions that echinoid diversification in the region occurred later, during the Miocene.

The study also raises intriguing questions about the role of the Caribbean as a migration corridor for marine life during the Paleogene. Were these Clypeaster populations early colonizers, or did they represent a more ancient lineage persisting through climatic shifts? Future research, including detailed morphological analyses and comparisons with other fossil sites, may help unravel the evolutionary pathways of these echinoids.

By documenting these fossils, this study contributes to our understanding of past ecosystems and the biogeographical history of echinoids. It also underscores the importance of Cuba’s fossil record in reconstructing ancient marine environments and refining our models of species distribution during critical periods of Earth’s history.

This work was made possible through the contributions of coauthors Carlos Rafael Borges-Sellén, Alberto F. Arano-Ruiz, Johanset Orihuela, and Yasmani Ceballos-Izquierdo, whose efforts in fieldwork, analysis, and writing were fundamental to this research. The full paper is available for download here.

The study is published in POEYANA, a peer-reviewed open-access journal (ISSN: 2410-7492, RNPS: 2403) that has been a cornerstone of zoological research in Cuba, the Caribbean, and the Neotropics since its founding in 1964. Originally established at the former Institute of Zoology of the Cuban Academy of Sciences, POEYANA is now edited by the Institute of Ecology and Systematics under the Ministry of Science, Technology, and Environment (CITMA). With over 500 published articles spanning more than five decades, the journal continues to serve as a platform for scientific contributions from Cuban and international researchers in the field of natural sciences.