A fly (Diptera: Nematocera) of the family Chironomidae (non-biting midges) trapped in a studied amber sample. Credit: Mónica Solórzano-Kraemer
The most extensive deposit of insect-containing amber ever uncovered in South America has been dug out of a quarry in eastern Ecuador.
The fossilised tree resin was formed 112 million years ago (mya) during the Cretaceous Resinous Interval (125–72 mya), a period characterised by extensive resin production by conifers.
New analysis of the materials has revealed the identity of the trapped insects and surrounding fossilised matter, providing new insights into the biodiversity and ecosystems of the southern hemisphere’s supercontinent Gondwana.
A beetle (Coleoptera: Tenebrionoidea) of the family Tetratomidae (polypore fungus beetles) trapped in a studied amber sample. Credit: Enrique Peñalver
“While common in the Northern Hemisphere, amber containing terrestrial arthropod inclusions had not previously been reported from the Mesozoic of South America,” write the authors of the study published in the journal Communications Earth & Environment.
“Here, we report the major occurrence of such amber from the early Albian (~112 Mya) Hollín Formation in Ecuadorian Napo region.”
The researchers found amber which formed underground around the roots of resin-producing plants as well as 60 samples of aerial amber – formed when resin becomes exposed to air.
Pieces of aerial amber found in the Genoveva Quarry, in Archidona, Napo Region, Ecuador. Note their stalactite-like, drip-like structure. Credit: Mónica Solórzano-Kraemer
It’s the second kind which can feature organisms that became trapped in the sticky resin, providing researchers a window into the past to study organisms which would not otherwise survive in the fossil record.
Microscope examination revealed 21 ‘bio-inclusions’ which included bugs from 5 insect orders – including Diptera (flies), Coleoptera (beetles), and Hymenoptera (which includes ants and wasps) – and a fragment of spider web.
The researchers also identified a wide variety of plant fossils in the surrounding rock samples, including spores, pollen, and other remains.
A fly (Diptera: Brachycera) of the family Dolichopodidae (long-legged flies) trapped in a studied amber sample. Credit: Mónica Solórzano-Kraemer
Together their analysis indicates the amber formed in a humid, low-latitude forest in the north-western part of Gondwana.
“This discovery and the associated plant remains in the amber-bearing rocks, enhance our understanding of the Gondwanan arthropod fauna and flora inhabiting forests along its western margin during a time interval of major ecosystem transformation,” the authors write.
“Future fieldwork exploration in the Hollín Formation of the Napo region [of Ecuador] is expected to yield new fossil bioinclusions which may improve our understanding of the biogeographic relationships between the South American fauna and flora and those of other Gondwana regions, such as Antarctica, South Africa, Australia and New Zealand, where amber is also present and need to be investigated.”
Pieces of amber in situ in level G1 of the Genoveva Quarry, Ecuador. This level, approximately 70 centimetres thick, contains thousands of amber pieces. Credit: Xavier Delclò