2024-02-13 15:45:04
From the period from 80 million years ago to 66 million years ago, there are hardly any insect fossils.
A group of Argentine paleontologists led by Fernando Novas, a researcher at the National Scientific and Technical Research Council (CONICET) at the Argentine Museum of Natural Sciences (MACN), found, among others, microscopic remains of butterfly larvae and scales, and fragments of heads and jaws of larvae of close relatives of mosquitoes that coexisted with dinosaurs in southern Argentina 70 million years ago. These are one of the few records of this antiquity worldwide.
While they were carrying out an expedition to make the most complete characterization possible of the ecosystem in which the dinosaurs lived, and reconstruct how the environment changed in the last million years of the Cretaceous period in an area of the province of Santa Cruz in which they already Valuable discoveries had been made, an interdisciplinary group of scientists from CONICET was surprised to find the first fossil remains of insects that lived in Patagonia shortly before the last mass extinction. There are very few records of this antiquity worldwide.
“For the time interval in which we are working – between 80 and 66 million years – the remains of fossil insects are practically non-existent, and in the region they can be counted on the fingers of one hand. In fact, most records of the presence of South American insects from the late Cretaceous are based on indirect evidence such as galleries or nests, and not on corporeal remains like those we found. There were also no previous records of aquatic insects,” renowned paleontologist Fernando Novas, CONICET researcher at the Argentine Museum of Natural Sciences (MACN) and leader of the expedition carried out in the Chorrillo Formation, located about 30 meters away, told the CyTA-Leloir Agency. kilometers south of the town of El Calafate.
“The Chorrillo Formation is one of the few in our country, and I would say in the world, that provides evidence of beings as varied as dinosaurs, mammals, birds, frogs, fish, snails, plants and, now, insects,” emphasized Novas, who considers that it is essential to investigate the entire ecosystem of the time and not just the most outstanding or gigantic ones.
“The dinosaurs did not live alone, but accompanied by a very wide range of organisms: in addition to animals and plants, there were also microscopic beings such as bacteria and viruses. We have to understand the integrity of this prehistoric biota,” added Federico Agnolín, CONICET researcher at the Laboratory of Comparative Anatomy and Evolution of Vertebrates (LACEV) of the MACN.
The team, led by Ezequiel Vera, a CONICET researcher in the Paleobotany Division of the MACN, found remains of insects from different groups. Among them, larvae and butterfly wing scales; fragments of heads and jaws of chironomid larvae (relatives of mosquitoes but do not feed on blood); remains of a mayfly larva (distant relative of modern dragonflies); and other indeterminable remains of arthropods. “We were mainly surprised by the extraordinary degree of preservation, as well as the diversity of the available remains consistent with different body parts. “We did not expect to find such a microscopic world!”, highlighted Vera.
Reconstruction, from fossil remains, of a lepidoptera, a group to which butterflies and moths belong. (Image: LACEV).
Although the objective of the expedition was to characterize the ecosystem, Vera recognized that the discovery of the insects was pure chance: the team of paleobotanists had collected about 60 rock samples, which they treated with acids to extract the organic matter and thus recover pollen grains and fern spores. “While they were examining them under the microscope, they began to see jaws, heads with eyes and hair, various types of legs and other very strange structures that did not belong to any plant, but clearly to insects,” Novas described. Palynologist Valeria Pérez Loinaze, Conicet researcher at the MACN and co-author of the work, clarified: “After the initial surprise, a methodical search for these remains was carried out and a large quantity was obtained.”
Based on this discovery, specialists in fossil insects Julieta Massaferro, from the Program of Studies Applied to the Conservation of Biodiversity CENAC/APN, from Bariloche, were summoned; and Oscar Gallego and Mateo Monferrán, from the Center for Applied Ecology of the Litoral, in Corrientes, who determined in detail the different types of insects found.
Another interesting contribution of the discovery has to do with the fact that it offers new evidence of the relationship between the fauna of the Australasian area and that of the southern tip of South America. It happens that the team led by Novas considers that the remains of aquatic insects are consistent with the presence of mammals related to the current Australian platypus, which lives in rivers and lakes and its diet includes snails and insects like those discovered in Chorrillo. In fact, last year another member of the team, paleontologist Nicolás Chimento, published the discovery at that same site of a small molar of a mammal very similar to the platypus.
“We do not know what type of ecological interaction would have existed between the dinosaurs, butterflies, chironomids and mayflies that we have found, but we can make an image of the platypus swimming among water lilies and capturing insects and snails similar to the one observed today in the Australian streams and lakes,” commented Novas.
Beyond knowing the environment in which the giants of the past lived, researchers also want to understand what effect the mass extinction at the end of the Cretaceous period had on the Earth’s ecosystems. “We know that the large dinosaurs disappeared forever, as did flying and marine reptiles, other groups of vertebrates and invertebrates, and plants. But we are still not clear how these biotic changes were related to each other,” Agnolín said. And he concluded: “The discovery of fossil remains that we present allows us to learn about some groups of insects that lived in the extreme south of Patagonia at that time and add data to evaluate the effects of the last mass extinction in the region.”
But that is not all. The experience of Argentine scientists can also be a warning to their colleagues around the world: they now know that when searching for plant remains in rocks they can also find animal records preserved in three dimensions, something that had not been taken into account until now. (Source: CyTA-Leloir Agency)
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