This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A remarkably diverse fossil ecosystem in central Colombia that preserves an unusual overlap between survivors of older Jurassic groups and newer Cretaceous lineages has led researchers at McGill University and the Centro de Investigaciones Paleontológicas (CIP) to recognize a new pattern of large-scale evolutionary transition, one that does not include mass extinctions. Based on their research on the Paja Formation, Ph.D. graduate Dirley Cortés and professor Hans Larsson of the Department of Biology propose the concept of a "biotic inflection," a period when many evolutionary lineages on the brink of extinction coexist with newly emerging groups that later diversify.
The researchers said they believe the extreme biodiversity and biological transition found in this formation were probably facilitated by a rare convergence of environmental conditions that included greenhouse temperatures, high sea levels, nutrient-rich coastal waters and new marine connections between the eastern Pacific and early Atlantic oceans through what is now Colombia. They noted that these are many of the same factors that drive biodiversity today. "The Paja Formation records an extraordinary process in the history of life, when a 'perfect storm' of environmental factors we know to promote ecological complexity coincided with ancient lineages that were about to disappear.
At the same time, new groups were beginning to flourish," Larsson said. The research is published in the journal Frontiers in Ecology and Evolution. The team identified the pattern in the Early Cretaceous Paja Formation near Villa de Leyva, Colombia, where the CIP houses most of its fossils.
"This geological formation has produced an exceptionally rich fossil record that includes giant marine reptiles like long-necked plesiosaurs and marine crocodile relatives, as well as turtles, sharks, crustaceans and others," Cortés explained. "Together, these animals formed the Paja Biota, one of the most ecologically complex marine communities found to date." The researchers had already estimated the Paja Biota's food web in a previous study and discovered it was one of the most complex to have ever evolved, with a high diversity of apex predators. Additional fossil sampling, more precise dating and comparisons with deposits elsewhere in the world will be needed to test how widespread the biotic inflection pattern was and when similar events may have occurred in Earth's history.
"I think we've discovered a new model of global biodiversity change. Now we'll need to see just how widespread this could be in Earth's history and how we can quantify its impacts," Larsson said. Dirley Cortés et al., The Paja Formation of Colombia records uniquely high biodiversity during a biotic inflection in an Early Cretaceous Gondwanan marine ecosystem, Frontiers in Ecology and Evolution (2026).
DOI: 10.3389/fevo.2026.1848892 Journal information: Frontiers in Ecology and Evolution Swati Mestri holds a bachelor's degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space. Full profile → Bachelor's in mathematical biology, Master's in creative writing.
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