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Just over 100 km from Madrid, not far from the A-2 motorway, it is difficult to imagine that large grazed dinosaurs sauropods and primitive marine reptiles and crocodiles swam in tropical coastal waters. They did it about 95 million years ago, early Upper Cretaceous, in what today is Algora, Guadalajara.
During a geology student excursion around the site, more than 25 years ago, one of the students found an isolated small carnivorous dinosaur tooth. Despite the exceptional find, interest in this fossil went unnoticed until six years ago, when a researcher from the National Distance Education University (UNED) noticed this discovery.
Since then, the UNED Evolutionary Biology Group has carried out a first paleontological intervention in 2016, together with other Spanish and foreign experts, and a second campaign has just ended in which more than 400 very well-preserved fossils of crocodiles, fish, plesiosaurs, turtles and titanosaurs, several of which could be new species to science.
"The fauna of Algora was very poorly known, given that it lived in a period for which little information is available for the whole of Europe, but which is fundamental to know how the establishment of the last faunas with dinosaurs and other contemporary reptiles took place. in this continent ”, says Adán Pérez García, principal investigator of the project.
The unique site not only completes the information on the last ecosystems dominated by dinosaurs in Europe, but also stands out for the abundance of its fossils, the preservation of the same and allows to identify poorly known species or new terrestrial vertebrates, freshwater, coastal marine, and open sea animals.
Scientists specifically emphasize the presence of turtles of the genus Algorachelus, of which there is still much to know and that partly motivated the project promoted by the Vice-Ministry of Culture of the Department of Education, Culture and Sports of Castilla-La Mancha.
The cretaceous fauna of Guadalajara
“The knowledge about Algorachelus can be radically improved, thanks to the discovery of numerous complete shells, both juvenile and adult individuals, but also the largest collection of skulls in all of Europe and one of the largest worldwide of the group to which this belongs turtle ”, details Pérez García.
In addition to the turtles, the campaign has brought to light the representatives of other previously poorly known lineages. "We have identified a greater diversity of fish than considered so far," says the scientist who has been able to recognize remains of fish of African origin.
This finding supports the hypothesis of the replacement of various European vertebrates by fauna from the southern landmass, called Gondwana and formed by Africa and South America. The first example of this dispersal was the Algorachelus peregrina tortoise, originating from what was now Africa and whose remains were found during the first campaign in Algora.
The successful excavation also shows the presence of various forms of crocodiles, of which very little information was had. “The new material allows us to recognize that some primitive crocodile lineages they still survived at the beginning of the Upper Cretaceous, along with forms attributable to more modern lineages, which ended up completely replacing them several million years later ”, says the paleontologist.
A partial skeleton of titanosaur
Algora's environment 95 million years ago was also the herbivorous dinosaur habitat. Far from being a desert environment as previously thought, the region was actually a tropical coastal area, with large forests, according to the great biodiversity of species discovered.
The group has in fact discovered a partial skeleton –vertebrae, elements of the girdle and limbs– of a relatively small herbivore, which could correspond to a new species of sauropod.
"It would be the oldest European representative of titanosaurs, which were one of the most abundant and diverse groups of dinosaurs in the deposits of the final part of the Cretaceous in this continent ”, indicates Adán Pérez García.
The analysis of the fossils will now allow us to know the origin of the European members of this lineage of sauropods, very common at the end of the period dominated by dinosaurs. "The possibility that the Algora sauropod is a new species is high, and the same may occur with representatives of other groups found during this excavation", concludes the researcher.