the route of urban fossils in the City

Paris stone-like facades, Spanish and French slate tiles, domes of all shapes and sizes, stained glass, mansards, oak floors, artistic ornamentation and ironwork. The palaces, buildings and residences of Buenos Aires -built between the late 1800s and the early decades of the 1900s- have some or all of these characteristics in common.

In addition, rocks and stones make up part of the covering of these constructions for which materials that had been traveling by boat were used, from different places in Europe, like the Alps and the Mediterranean; and even from India or the Middle East.

Along with these rocks and stones, they also “traveled” Fossil remains that can still be seen today in the foyer and in the main room of the Colon Theaterin the entrance hall of the House of Culture, and also in the Palace of the National Congress and in the Bicentennial Museum. The Savoy Hotel, the Basilica of San José de Flores, the Meteorological Column of the Botanical Garden also have traces of species that inhabited the Earth millions of years ago.

They are there, visible to everyone, but they usually go unnoticed. How did they arrive? From where? Can you tell how old they are? What type of organism were they?

The paleontologist Horacio Padula gave some clues to know where to see and find them: “In the Teatro Colón and the Meteorological Column of the Botanical Garden, for example, you can see bivalves; like the clams, cockles or mussels that we know today. But these bivalves, which were the main reef-forming organisms in the Cretaceous Period -now this function is fulfilled by corals-, they had very particular shapes: one of the valves was conical and was the one that rested on the ground, while the other valve was flat and formed a kind of lid.”

Padula is deputy operational manager of Heritage and Archeology, an area whose purpose is the development of activities aimed at advising, surveying, registering and preserving the tangible heritage of the City. The organization depends on the Heritage Operational Management and the General Directorate of Heritage, Museums and Historic Center.

Explain that this group of bivalves are known as rudists; They appeared in the Upper Jurassic (began 163.5 million years ago and ended 152.1 million years ago) and disappeared at the end of the Cretaceous (a period that ended 66 million years ago) along with the great extinction of the dinosaurs.

Fossils are not only found in palaces and ancient buildings. They can also be found on the paths surrounding the Galileo Galilei Planetarium, in Palermo: in addition to seeing distant planets and stars through telescopes, you can see ammonites. What were they? “Cephalopod mollusks, similar to current octopuses and squids, but lived inside a shell. Precisely this shell is the part that has been fossilized,” says Padula.

And it provides a curious fact: they were cosmopolitan, that is, they could be found in all the seas of the world. They inhabited the planet from the Devonian Period (began 417 million years ago and ended 354 million years ago, it is the third period of the Paleozoic Era) until the great extinction of the Cretaceous.

During the pandemic, a paleontologist made an unprecedented discovery also on the paths of the Planetarium: he found bones of a fish unique to the region. This is a new species from the Jurassic of Neuquén. The rock was extracted and will soon be presented as a scientific novelty. It is worth clarifying that this province has a huge number of deposits; There are frequently findings from research, but also chance findings. As happened a few days ago, when a boy found the hind leg of a herbivorous dinosaur.

There are riots too on the floor of the Cenotaph to the Fallen in Malvinas, in Plaza San Martín; at the Teatro Colón; and at the Savoy Hotel, at Callao 181. At the entrance of this establishment, you can see a dozen of them.

As said, the House of Culture -former Diario La Prensa-, has traces of nummulites in its coverings: “They were unicellular marine organisms that lived between the upper Paleocene and the lower Oligocene (belonging to the Paleogene Period, between 65 and 40 million years before the present). The shell is what is preserved as a fossil and could reach 5 centimeters in diameter. It looked like a coin, which is why it is informally known by this name. what was the entrance of the carriages, along with others remains of coral skeletons, sponges, bryozoans and bivalves, among others”Padula says.

and share with Clarion another curiosity: the same fossil abounds in the rocks of the pyramids of Egypt. “So it is also an urban fossil there since it is part of a construction,” concludes the paleontologist.

Ezequiel Vera is also a paleontologist, researcher and works at the Bernardino Rivadavia Argentine Museum of Natural Sciences, in Parque Centenario. His expertise is fossil plants and he is definitely curious about the entire universe linked to this topic. On his social networks he made a publication that surprised many X users and received thousands of likes: he visited the shopping center in the Saavedra neighborhood for the first time, the DOT, and found tiles full of fossils.

His post had many messages. Some asking for more data about the fossils; others were incredulous, not understanding how the fossils had gotten there; Some took the opportunity to share photos of coverings that once caught their attention, such as the stairs of the Central Military Hospital, or sidewalks in the suburban neighborhoods; “And here I thought they were remains of gum and dirt.”someone also commented on the post.

“Extinct fauna and flora have always generated interest in people. It is a striking topic, it provokes a lot of curiosity. And on the other hand, in the case of these fossils, They are there, in plain sight, by hand, they are part of the places we move through all the time and I think this also arouses attraction,” Vera told Clarion.

Always willing to disseminate and communicate about this universe, he has just opened an account (@fosilesurbanos) to map the fossils of Buenos Aires and the entire country. People can upload photos and location.

There are three types of rocks that have been commonly used in construction: igneous, sedimentary and metamorphic. Regarding the former, Padula explains that they have greater hardness and resistance than others. The sedimentary ones were also cheaper and are where the largest number of fossils are seen. The metamorphic ones also have a lot of presence in the City. Each one, with its texture and color characteristics, adds beauty to the coatings.

How do these sedimentary rocks come to have fossil remains? In the work “Urban fossils, paleontology between buildings and streets”, Padula and the doctor in Geological Sciences Dario Lazo, detailed that rocks are formed by the accumulation and consolidation of sediments deposited on an extensive surface, such as the bottom of a sea ​​or a lake. The organisms that lived in those places ended up being buried by sediments and, if the circumstances were favorable, they were preserved over time, giving rise to fossil remains. Identifying them allows us to know the age of the rock and the characteristicsfor example, if it was submerged in fresh or salt water, in deep water or on the coast.

The Recoleta cemetery is another site with a large concentration of fossils and Heritage and Archeology began working on a survey and on a map that can geolocate them. Thus they would provide a new tourist attraction to the historic Buenos Aires holy field and the one that concentrates an authentic heritage collection of small-scale constructions: vaults, tombs and pantheons.