They find in Colombia the first flat-toothed shark in America – Science – Life

Who is not afraid of a close encounter with the sharp teeth of a shark? In popular culture, films such as those by Steven Spielberg managed to create for these animals a reputation—largely undeserved—of fearsome man-eating monsters with an arsenal of knives capable of ripping and tearing apart people’s limbs. However, not even current sharks have a special predilection for including mammals as small as humans in their diet, nor have they always had those distinctive teeth that you know in their 400 years of life and evolution on the planet.
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Although it is difficult to imagine, hundreds of millions of years ago there were also sharks with flat teeth, like pieces of dominoes. Its fossil traces had been found by scientists in European and African countries, and now for the first time there is a confirmed record of one in American territory, more precisely in Colombia, in the municipality of Zapatoca, in Santander.

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It is also a new species, described by Dr. Edwin Cadena, paleontologist and director of the Earth System Sciences program at the Universidad del Rosario, together with his colleague from the University of Zurich, Switzerland, Dr. Jorge Carrillo. A work that is published today in the international public access journal PeerJ, and that once again puts the eyes of paleontologists around the world on the contributions that Colombia has been making to this science in recent years.

baptized as Strophodus rebecae this particular shark lived about 135 million years ago in the sea that covered what is now Colombia, during the geological period known as the early Cretaceous. A world dominated by dinosaurs and large marine reptiles.

Dr. Edwin Cadena on a field trip in Zapatoca.

His description was achieved thanks to numerous teeth that Cadena had collected over the years during his fieldwork in Zapatoca, where he is from. Once he and Carrillo considered that they had a sufficient arsenal of similar pieces, they decided to ‘put their teeth’ into the matter, confesses Cadena, who has also participated in important discoveries in Colombian territory, such as that of the Titanoboa cerrejonensiswhich is considered the largest snake in the world, and the Desmatochelys Padillaithe oldest sea turtle on record.

“We started to realize that just like with humans, we don’t need to have a skeleton to be able to tell if it’s a new species or not. We have had hominid species defined only with the jaw and teeth, our dental chart is unique in a certain way and the same happens with certain groups of animals, such as these sharks, that the teeth are very particular”, explains Dr. Cadena.

In addition, because it is almost the only piece that those who study this type of animal have, the rest of the skeleton does not exist in the fossil study of most ancient sharks because there is no ossification. In this case the teeth become key pieces to define a new species, as

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cardigan stropodus

Sample of one of the flat teeth of the new species of shark.

tracks around the world

To reconstruct the identity and history of this shark, Cadena and Carrillo started from the analysis of the samples they had collected. “The advantage is that we had many pieces, an interesting statistical population where we could see the variation of the characteristics of the teeth and say if they were consistent or not. We had teeth that were even broken and they allowed us to see inside naturally, what the variation of the dentin (the tissue that is immediately under the dental enamel), the enamel or the root was like, ”says the paleontologist Cadena.

This allowed them to know in depth the population of this Colombian shark to be able to compare it later with the record that has been made of its foreign relatives in other scientific publications and with collections in Germany, Switzerland and Austria. Thus, they determined that some characteristics of the teeth they were studying, such as the shape of the cusps or protruding tips, were totally different from the rest of sharks that had been found in the world.

“However, it does share some particularly European details and that is why it is of the same gender, strophodusbut the species is new”, says Cadena, who highlights this new animal’s particular teeth as an interesting detail that breaks with the stereotype of a shark with sharp, triangular teeth, perfect for cutting, breaking and tearing.

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“Not everyone has been like that. Sharks through time have had different evolutionary and ecological adaptations, and this is one of them. These sharks that we found were not adapted to tear but rather to crush and that is why their teeth are flat”, details the expert. And he continues: “What they did was that when the prey came, they closed their jaws and, instead of generating that rip, they caused a crush.”

This allowed them to feed on the proliferation of invertebrates that at that time inhabited with Strophodus rebecae on the marine platform. Animals such as the extinct molluscs known as ammonites, jellyfish and everything that had a shell that hid a soft part inside, ideal food for these sharks.

Although as predators they were surely surpassed by large animals with sharp teeth such as plesiosaurs, ichthyosaurs and marine crocodiles, of which fossils have also been found in Zapatoca. An ancient marine ecosystem that was recreated for this research by the Argentinean paleoartist Jorge Blanco, who put Strophodus rebecae along with these and other animals that have appeared in Santander, such as the turtle Notoemys Zapatocaensisrioters and sea urchins.

Stropodus rebecae

Representation of Strophodus rebecae and other animals of the ecosystem in which it would have inhabited.

Zapatoca

In fact, this Santanderean municipality has established itself as one of the most iconic fossiliferous localities in Colombia. A place where there is evidence of what life was like in this part of the world 135 million years ago, remains much older than those found in Villa de Leyva or any other site in the country.

What attracts paleontologists from Zapatoca is that their fossils correspond to a time when changes were taking place on Earth, such as the opening of the Atlantic Ocean and the separation of South America from Africa. “All the continents begin to move, to move and understanding how that impacted life, in the fauna of both reptiles, fish and turtles, is key. This place can help us connect what happened in North America, Europe, Argentina and Africa with what happened in the north of South America”, explains Cadena.

(Also read: The oldest tropical dry forest in South America is in Colombia)

For this reason, findings such as Strophodus rebecae they become another piece of the puzzle that the scientific community is trying to reconstruct, which shows that some of the European faunas, like this shark, also had a presence in what is now America, although with small variations.

But the importance of the discovery of this flat-toothed shark also has to do, on a more local level, with expanding the knowledge of the history of the diversity of plants and animals present in tropical ecosystems such as that of Colombia. “We know that the tropics are biodiverse today and thanks to the plants we have known that this biodiversity has been there for 60 million years, but we know little about much further back. 100 or 120 million years ago, what were food chains like? Who ate whom? Were they ideal places for the proliferation of different species? This also answers as a part of that question”, assures Cadena.

And what does it represent for Zapatoca? This place where the remains of some of the best marine crocodiles and turtles in Colombia have been found, despite its paleontological relevance, does not yet have a museum where its inhabitants can learn about its history. For Chain Strophodus rebecae It must be a motivation to materialize it. At the same time, this animal became a tribute to one of the inhabitants of this municipality: Cadena’s mother, Rebeca Rueda, from whom this new species receives its name and who for him has indirectly contributed to the advancement of this science in the country with the hospitality that he has offered to many of the most important Colombian paleontologists, who have found in his house an obligatory stop to study the secrets of the region’s fossils.

MARIA ALEJANDRA LOPEZ SQUARES
SCIENCE EDITOR
@malelopezpl
@TimeofScience

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