# Colombian Fossils Reveal a "Biotic Inflection": Evolution Turned Over Without a Mass Extinction

*2026-11-12 23:00 UTC · Science · 1 min read*

> A McGill-led study of the Early Cretaceous Paja Formation finds old and new marine lineages overlapping in one rich ecosystem, suggesting major transitions need no mass extinction.

Researchers led by McGill University and Colombia's Centro de Investigaciones Paleontológicas have described a previously unrecognized pattern of evolutionary change, based on fossils from the Early Cretaceous Paja Formation near Villa de Leyva. They call it a "Biotic Inflection": a period when older lineages approaching extinction overlap with newer groups that are just starting to diversify, with no mass extinction in between.

The assemblage, named the Paja Biota, preserves survivors of older Jurassic groups alongside newer Cretaceous lineages, including giant marine reptiles and sharks. It is considered one of the most ecologically complex marine communities found to date.

The authors attribute the richness to a rare mix of conditions: greenhouse temperatures, high sea levels, nutrient-rich coastal waters and new marine links between the eastern Pacific and the early Atlantic. They say more fossil sampling and more precise dating are needed to learn how widespread the pattern is.

## Sources

- [sciencedaily.com](https://sciencedaily.com/releases/2026/11/261106174535.htm)
- [eurekalert.org](https://www.eurekalert.org/news-releases/1149826)

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TechTools News · https://techtools.cz/tools/news/article/2680-colombian-fossils-reveal-a-biotic-inflection-evolution-turned-over-without-a
Česká verze: https://techtools.cz/tools/news/clanek/2754-fosilie-z-kolumbie-odhaluji-biotickou-inflexi-evolucni-obmena-probehla-bez