2023-11-03 22:45:26
A paleontological find in the Argentine province of La Rioja reveals more than 70 footprints, left by small animals 15 million years ago, in a period known as the Miocene.
Researchers, based on the analysis of fossil footprints, have managed to identify the basic characteristics of a fauna of small and diverse animals that lived at that time.
“At that time, in the geological period known as Miocene, the fauna was very varied and unique, since South America was isolated from other continents, as Australia is today,” he explains, in dialogue with the CTyS-UNLaM Agency, Verónica Krapovickas, work leader and CONICET researcher at the “Don Pablo Groeber” Institute of Andean Studies (IDEAN, UBA-CONICET).
The team says that, among other things, the discovery made it possible to identify various species from that time. “We found tracks of a dynomid rodent that could measure up to a meter in length. There were traces of macrauchenids, which are extinct mammals that have no current evolutionary relatives, but, due to their size and shape, they would be comparable to guanacos. There were also footprints of giant sloths that measured up to 6 meters, and of jumping mammals, very similar to today’s rodents,” explains Martín Ezequiel Farina, member of the team whose study is published in the academic journal Journal of South American Sciences.
The researchers also identified, from the study of the footprints, small freshwater turtles and large ratite birds, similar to rheas.
By finding all the footprints on a single surface, scientists can infer that all these animals lived together, since the time involved in the formation of this surface is very little, possibly weeks. “Therefore, we are sure that these animals were part of the same community and the same ecosystem. In the case of footprints, it is much more direct or easier to know that the animals coexisted,” remarks Krapovickas, a member of the Argentine Paleontological Association (APA).
For the project director, the finding also stands out in relation to the time of the records. “The footprints are between 15 and 12 million years old, which we know through absolute U-PB radiometric dating. “This is a scientific method that is used to determine the exact age of rocks and minerals, taking advantage of the radioactive decomposition of uranium into lead and calculating the time that has passed since the materials were formed,” says the CONICET researcher.
Thus, these traces, the researchers say, speak of a fauna from an age about which much less is known than about the previous and subsequent ages, such as the Early Miocene and the Late Miocene.
The area where the fossil footprints have been found. (Photo: the research team)
There are so many variables involved in paleontology that interdisciplinary views become essential. “Both in the field study and in the subsequent data analysis, this aspect is vital. The new discovery, for example, was thanks to the work of a group of geologists who work in the area studying what the environments were like at that time. They gave us the information and based on their work we planned our trip,” he mentions. For example, Farina.
Furthermore, the volume of data and the breadth of computer tools that exist was such that the researchers decided to include in the work team a mathematician from the University of San Andrés and an engineer from the University of Erlangen, Germany.
“Together with them, we are establishing novel work areas, until now little explored, to investigate how animals moved in the past. An interdisciplinary work is not only richer, but it also allows you to explore other aspects of your field and ask questions that would never have occurred to you,” argues Krapovickas.
In this sense, researchers say that paleontological work begins, logically, with the search for fossil-bearing sites. “In the first instance, the inspection of geological maps is the trigger to locate the strata of the age of interest, as well as the consultation of historical bibliography. Many times, the exchange with colleagues is key to visiting new places and prospecting,” summarizes Rocío Vera, member of the team.
Once the destination is chosen, the organization of field work begins. “Experiences are as variable as the places where you work. The trip, transportation, stay, accessibility to the site, the way of working in the field with fossils and even the eating styles depend on the place where you work,” as Vera explains. “In the case of fossil footprints, field work is somewhat simpler than the extraction of corporeal fossils; However, the most work is done on site with the analysis of the surfaces that carry fingerprints.”
With the footprints, not only the shape they present is analyzed, but also their quality of preservation, the sediment where they are kept and the sedimentary structures that may be present, among other criteria. Measurements are also taken of both tracks and scrapes, which can be indices of the animals’ body characteristics, such as body length and width.
Since the extraction of fossil footprints is often difficult, taking photographs and making molds, with plaster or silicone, are key for subsequent laboratory study. “And, in the same laboratory, three-dimensional models can be made from photographs taken in the field, and these models are very helpful when analyzing the characteristics of the footprints that escape observation in the field. Three-dimensional scans can be made from the molds to obtain these models,” concludes Vera. (Source: Nicolás Camargo Lescano / CTyS-UNLaM Agency)
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