Face to Face with the Giants of the Pampean Plains

Methods

Summary

First, we will travel to General Guido, transporting all the necessary equipment. To do this, we will create a list of all the supplies and tools we’ll need based on previous fossil extraction and cleaning experiences. To ensure our planning is accurate, we will consult colleagues with extensive experience in similar projects.

Once on site, the most challenging part to clean is the inner side of the shell. To access it, we need to turn the shell over using heavy machinery (e.g., backhoes, forklifts). This process will be carried out with the help of technicians and engineers from the General Guido Department. Once the shell is flipped, it will be emptied, and both the sediment and the skeletal remains will be carefully removed. As the bones are extracted, we will document the original position and location of each one.

After the shell is emptied, it will be reinforced internally using special adhesives and resins. This will ensure that the fossil does not collapse under its own weight and can withstand the external preparation and analysis to follow. For the external preparation, we will begin by carefully removing the protective plaster to expose the fossil. Any exposed areas of the shell will be immediately cleaned and reinforced to prepare them for the next steps. Then, areas still covered in sediment will be cleaned using carbide tips, spatulas, and small brushes, and subsequently stabilized using special adhesives. Special emphasis will be given to the preparation of the head, in order to discover and later reconstruct the possible facial armour of these animals.

Once each part is separated and cleaned, we can proceed with the study. Each bone and part of the carcass will be examined in detail under magnification, paying particular attention to abnormal anatomical features such as rough textures, swellings, and marks. The formers may correspond to the insertion of soft tissue structures such as a trunk, while swellings and marks could preliminarly indicate infections or reactions to bites of parasitic insects.

We will also take thin sections of bone (less than 1 mm thick) for histological analysis to study bone structure. This will help confirm the nature or cause of observed anomalies. For instance, the presence of Sharpey’s fibers in roughened areas would support the hypothesis of a trunk. Another goal of histology is to corroborate whether the individual suffer or not parasitic infections.

Additionally, small bone samples (less than 1g) will be taken for isotope analysis. By measuring oxygen and carbon isotopes, we can infer the types and quantities of plants consumed—such as succulents, grasses, or shrubs.

Finally, all these results will be compiled into a scientific paper presenting new findings about this animal. We will also share the results with the General Guido community through public talks, workshops, and lectures. The goal is to promote appreciation of local heritage and inspire young people to pursue science.

Challenges

The first and most significant challenge will be achieving a correct preparation of the shell. Therefore, it is crucial to obtain all the necessary supplies for cleaning and reinforcing the shell. Additionally, the cleaning process will not be done all at once; instead, the shell will be gradually consolidated as it is cleaned to prevent collapse. Once the shell is emptied, it will be reinforced with special adhesives.

Another potential challenge is transporting the specimen to Buenos Aires. To prevent fractures, each piece will be carefully wrapped in special fabrics and nets to ensure safe delivery to the museum.

In terms of research, the main concern is the possibility that some analyses may not yield expected results. For instance, anomalies in the bones (roughness and swellings) were observed during extraction. However, as is often the case in science, histological and isotopic analyses can sometimes produce inconclusive or ambiguous results. To mitigate this, we plan to conduct multiple tests of the same analysis. Our budget accounts for at least three repetitions per analysis to ensure the reliability of the results.

Pre Analysis Plan

Anomalous structures will be described and photographed in detail, and then compared with published cases. For example, in the case of roughness caused by infections resulting from insect bites, similar examples in other glyptodonts (as well as in both fossil and extant animal) swill be researched in the literature. Similarities and differences will be examined in both their external anatomy and histological features. Our hypothesis is that these rugosities were caused by flea bites.

For the possible presence of a trunk, the distribution of the marks and areas of swollen bone will be documented. These structures will be compared with living animals that have trunks, such as elephants or tapirs. Histology will be key to compare the microanatomy of these species with that of Panochthus. The analysis will also be replicated with animals that lack trunks, such as deer or armadillos. These comparisons will be based on published information and, if necessary, on histological sections of specimens housed in the Mammalogy Collections of the Museum of Natural Sciences. Our hypothesis is that Panochthus possessed a short trunk or snout.

Similarly, thin sections of the long bones will be used to determine the age and growth rate of the individual. These results will be compared with previously published data to identify similarities or differences with smaller close relatives. Our hypothesis is that, due to its larger body size, Panochthus grew at a faster rate than species such as Glyptodon.

Regarding facial armour, the distribution and shape of osteoderms (bony plates embedded in the skin) on the skull will be documented during the preparation process. These osteoderms were observed preliminarily during the excavation. Their anatomy will be described in detail, with particular attention to their spatial arrangement along the face. This potential facial armour will be reconstructed and compared with documented cases in related taxa (e.g., Glyptodon). Our hypothesis is that these osteoderms formed a true protective shield over the animal’s face.

Finally, after sampling and isotopic analysis, the values of carbon (δ¹³C) and oxygen (δ¹⁸O) in the samples will be evaluated. The δ¹³C values may reflect the types of plants consumed, since plant groups leave different isotopic signals depending on their photosynthetic pathway. For example, δ¹³C values between -9‰ and -15‰ would suggest a diet composed primarily of grasses. Likewise, δ¹⁸O values can provide insight into the prevailing climate conditions, with higher values generally indicating hotter or drier environments.