# Ancient Colombian Fossils Reveal New Evolutionary Model Researchers identify a Biotic Inflection where declining and emerging species coexist peacefully. - **Source:** [Latest Science News -- ScienceDaily](https://brifing.si/source/0eef8637-6c5b-4e79-8f5b-6c9c6b36cf16) - **Published:** 2026-11-08 - **Topic:** [science](https://brifing.si/c/science) - **Original article:** - **On Brifing:** https://brifing.si/s/ec17d8c7-e530-4217-af5e-8cc928b4f6cf ## Evolutionary Transition Discovery Researchers from McGill University and the Centro de Investigaciones Paleontológicas identified a unique evolutionary pattern in Colombia's Paja Formation. This site preserves an unusual mixture of Jurassic lineages nearing extinction alongside emerging Cretaceous groups. The findings challenge the traditional view that major biological transitions must be driven by widespread mass extinction events. ## Defining Biotic Inflection Biology professor Hans Larsson and researcher Dirley Cortés introduced the term Biotic Inflection to describe this phenomenon. It represents a specific turning point where older, declining animal groups coexist with newer, diversifying lineages. This model suggests that ecosystems can undergo profound changes through periods of high diversity rather than sudden, catastrophic collapse. ## Environmental Drivers of Diversity The coexistence of these diverse groups was likely supported by specific environmental conditions in the ancient ocean. Warm greenhouse temperatures, elevated sea levels, and nutrient-rich coastal waters created a stable habitat. These factors, combined with new ocean connections between the eastern Pacific and early Atlantic, fostered a highly complex marine ecosystem. ## The Paja Biota Complexity The Paja Formation provides a detailed record of the Paja Biota, an exceptionally complex community of prehistoric marine life. Fossils found in this region include giant long-necked plesiosaurs, marine crocodile relatives, turtles, and sharks. These species formed an intricate food web featuring a high variety of apex predators occupying the highest levels. ## Analyzing Ancient Feeding Relationships Previous studies reconstructed the feeding relationships among the animals within the Paja Biota to understand their interactions. The analysis revealed that the ecosystem supported an unusually large number of apex predators simultaneously. This complexity makes the formation a vital resource for studying how ecosystems shift as evolutionary groups decline and emerge. ## A Perfect Ecological Storm Larsson describes the conditions at the Paja Formation as a perfect storm of environmental factors that promote ecological complexity. By coinciding with the decline of ancient lineages and the rise of new ones, these conditions allowed for a rare snapshot of transition. Many of these environmental influences still shape global biodiversity today. ## Future Research and Validation While the Biotic Inflection model offers a new way to understand biodiversity, researchers emphasize that more evidence is required. Future work will focus on identifying similar patterns in other geological formations worldwide. Accurate dating of fossils and broader comparative studies will help determine how common this evolutionary transition model truly was. ## Significance of the Findings This discovery provides a potential new framework for interpreting Earth's history of biodiversity change. By quantifying the impacts of these transitions, scientists hope to better understand the mechanisms behind ecological shifts. The research was supported by multiple organizations, including the Natural Sciences and Engineering Research Council of Canada and the Smithsonian. ## Sources covering this story - https://www.sciencedaily.com/releases/2026/11/261106174535.htm — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._