A groundbreaking discovery in the remote province of Napo, Ecuador, has unveiled the first-ever Mesozoic amber deposit containing exquisitely preserved insects in South America. This remarkable find, dated to approximately 112 million years ago during the Albian stage of the Lower Cretaceous, provides an unprecedented glimpse into the ecosystems of the ancient southern hemisphere at a critical juncture in Earth’s geological history. At a time when the supercontinent Gondwana was fragmenting and diverse reptiles dominated terrestrial habitats, this amber deposit offers a unique window into the lush, humid tropical rainforests that once thrived in the region.
The amber, trapped within the Hollín Formation — a sedimentary sequence rich in organic material and known as an oil source rock — originates from what was once a fluvial-lacustrine (river and lake) environment. Geochemical and palynological evidence suggests that resin-producing trees responsible for the amber were primarily araucariaceous conifers. These evergreen conifers, part of an ancient lineage now scattered across the Southern Hemisphere, exuded resin which, upon fossilization, encapsulated a wide diversity of terrestrial arthropods, preserving them with remarkable fidelity for millions of years.
Among the bioinclusions identified within the amber samples are representatives from at least five orders of insects, including Diptera (flies), Coleoptera (beetles), Hymenoptera (ants and wasps), alongside a fragment of an ancient spider web. The presence of these insects strongly suggests that the palaeoenvironment was a thriving tropical rainforest rich in biodiversity. Notably, the discovery of rare wasp families such as †Stigmaphronidae underscores the uniqueness of this assemblage and offers new avenues for studying insect evolution in Gondwanan ecosystems.
While no plant remains were found within the amber itself, extensive fossilized plant material was uncovered in the surrounding sedimentary rocks. These included spores, pollen grains, and leaf fossils, which collectively reveal a dense forest dominated by ferns, cycads, and early angiosperms, alongside conifers from the Araucariaceae and Cheirolepidiaceae families. This vegetation mosaic paints a picture of a humid, diverse forest environment markedly different from contemporaneous arid regions documented elsewhere in South America, such as the Crato Formation.
Intriguingly, the amber shows two distinct formation types: one formed below ground near the roots of resin-producing plants, which notably lacks inclusions, and another type formed above ground where resin was exposed to the air, capturing insects and other materials. This duality provides insightful data on resin secretion behaviors and environmental conditions influencing amber formation in ancient ecosystems. Furthermore, chemical studies reveal that the amber has undergone maturation and alteration through exposure to oil, a process naturally occurring in source rocks within the Hollín Formation, which is currently exploited commercially.
The ecological implications of these findings are far-reaching. The arthropod community, rich in aquatic and terrestrial components, indicates the proximity of freshwater bodies within this rainforest, consistent with the depositional environment inferred from sedimentology. The presence of chironomid and ceratopogonid fly species—both groups closely associated with freshwater habitats—further supports this interpretation. This composition not only provides insights into the ecological niches of Cretaceous tropical rainforests but also into the evolutionary trajectories of these insect groups in Gondwana.
Adding another layer of complexity to the forest’s ecology, traces of epiphytic and resinicolous fungi have been detected on the fossilized leaves and within resin deposits. This evidence hints at intricate biological interactions, such as fungal symbiosis and decomposition, occurring within the canopy and resin flows of these ancient forests. Such findings offer a tantalizing glimpse into the microecosystems that supported biodiversity and nutrient cycling over a hundred million years ago.
Unlike many northern hemisphere amber deposits from the same era, which often bear signs of frequent wildfires, this Ecuadorian amber shows no evidence of fire activity, reinforcing the interpretation of a persistently humid and relatively stable forest ecosystem. This climate contrast highlights the varied environmental conditions that existed in different parts of Gondwana during the Cretaceous and emphasizes the importance of this discovery in filling geographical and ecological gaps in the amber fossil record.
The collaborative international research team involved in this discovery included experts from institutions across Spain, Ecuador, Panama, Colombia, and Germany. Through detailed analyses combining fieldwork, microscopy, geochemistry, and palynology, the study not only characterizes the amber and its inclusions but also situates the find within a broader paleobiogeographical context. This research paves the way for future excavations that could unveil connections between South American biodiversity and other Gondwanan landmasses such as Antarctica, Australia, and South Africa, where similar Cretaceous amber deposits have been located.
Ultimately, this novel discovery challenges prevailing notions about Mesozoic tropical rainforests in the southern hemisphere and their ecological complexity during the critical interval when flowering plants began to diversify and shape terrestrial ecosystems. The amber and its fossilized inhabitants reveal a richly intertwined forest system thriving in the shadow of continental drift, portending a wealth of untapped knowledge buried within Gondwana’s sedimentary basins.
Ongoing and future research building on these findings holds promise for further decoding the evolutionary history of insects, plants, and fungi during the Cretaceous, shedding light on ancient climatic patterns and biogeographical links that shaped Earth’s biodiversity. This amber deposit from Ecuador stands as a crucial piece of the puzzle in understanding how life on continents fragmented from Gondwana adapted, diversified, and flourished under the lush canopies of primeval tropical forests.
Subject of Research: Not applicable
Article Title: Cretaceous amber of Ecuador unveils new insights into South America’s Gondwanan forests
News Publication Date: 18-Sep-2025
Web References: http://dx.doi.org/10.1038/s43247-025-02625-2
References: Communications Earth & Environment, 10.1038/s43247-025-02625-2
Image Credits: UNIVERSITY OF BARCELONA
Keywords: Earth sciences
