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New research has shown that ancient plant fossils scientists have mistaken for are not actually plants.
Instead, the small round shapes with a leaf pattern were the shells of baby turtles that lived during the time of the dinosaurs. Scientists have nicknamed the turtle species “Turtwig,” after a Pokemon character that is half-turtle, half-plant.
The discovery marks the first time a baby turtle carapace has been found in northwestern South America, according to the study authors.
The results of their research were published Thursday in the journal Palaeontologia Electronica.
“In the Pokémon universe, you come across the concept of combining two or more elements, such as animals, machines, plants, etc.,” said lead author Héctor Palma-Castro, a paleobotany graduate student at National University of Colombia, in a statement.
“So when you have a fossil that was originally classified as a plant that turns out to be a baby turtle, a few Pokémon immediately come to mind. In this case, Turtwig, a baby turtle with a leaf attached to its head.
But it took some sleuthing to solve the paleontological mystery that began decades ago.
Wrong place, wrong time
It all started when Colombian priest Padre Gustavo Huertas discovered the fossils in the Paja Formation. The formation is part of one of Colombia’s geological heritage sites known as the Marine Reptile Lagerstätte of the Ricaurte Alto.
Previous fossil finds from the site include dinosaurs, plesiosaurs, pliosaurs, ichthyosaurs, turtles and crocodilian relatives known as crogallopmorphs dating from the Early Cretaceous Period, between 113 million and 132 million years ago.
Huertas collected fossils and rocks at the site, near the town of Villa de Leyva, from the 1950s to the 1970s. When he found the leaf-patterned rocks, he thought they were a fossil plant. Huertas described the specimens as Sphenophyllum colombianum in a 2003 study.
But other scientists were surprised to hear that the plant was found in northern South America and was dated between 113 million and 132 million years ago. The now-extinct plant, once common around the world, died out more than 100 million years ago, according to the fossil record.
Previous research into the plant showed that its leaves were usually wedge-shaped with veins radiating out from the base of the leaf.
The age and location of the fossils intrigued Palma-Castro and Fabiany Herrera, assistant curator of paleobotany at the Negaunee Integrative Research Center at the Natural History Museum in Chicago.
Herrera collects and studies plants from the Early Cretaceous Period (100.5 million to 145 million years ago) in northwestern South America, a part of the continent that receives little paleobotanical research.
The two fossils, about 2 inches (5 centimeters) in diameter, were kept in collections at the department of geosciences of the National University of Colombia. As Herrera and Palma-Castro examined the fossils and took photos, they thought something looked strange.
“When you look closely, the lines seen on the fossils don’t look like plant veins — I was positive it was probably bone,” Herrera, the study’s senior author, said in a statement.
Solving the mystery of a fossil
Herrera contacted his colleague Edwin-Alberto Cadena, a senior lecturer and paleontologist who studies turtles and other vertebrates at Del Rosario University in Bogotá, Colombia.
“They sent me the photos, and I said, ‘This definitely looks like a carapace’ – the upper bony shell of a turtle,” Cadena, a study co-author, said in a statement. “I said, ‘Well, this is amazing, because not only is this a turtle, but it’s a hatchling, it’s very, very small.'”
Cadena and one of his students, Diego Cómbita-Romero at the National University of Colombia, compared the fossils to other extinct and modern turtle shells.
“When we saw the specimen for the first time, I was surprised because the fossil was missing the typical markings on the outside of a turtle’s shell,” study coauthor Cómbita-Romero said in a statement. “It was a bit concave, like a bowl. At that moment we realized that the visible part of the fossil was on the other side of the carapace, we were looking at the part of the shell that is inside the turtle.”
During their analysis of the shells, the researchers determined that the turtles were about 1 year old at most when they died.
As young turtles develop, their growth rates and sizes can change, Cómbita-Romero said. But the remains of young turtles are rarely found because the bones in their shells are so thin.
“These turtles are probably related to other Cretaceous species that were up to fifteen feet long, but we don’t know much about how they grew to such enormous sizes,” Cadena said in a statement.
The researchers did not blame Huertas for mistakenly categorizing the fossils as plants. What he believed to be the leaves and stems were the vertebrae and ribs inside a turtle shell.
“We solved a small paleobotic mystery, but more importantly, this study shows the need to re-study historical collections in Colombia. The Early Cretaceous is a critical time in the evolution of land plants,” said Herrera.
The aim of the research team is to find the forests that once grew in the region, he said.
“In paleontology, your imagination and your ability to guess are always tested,” Palma-Castro said. “Discoveries like this are really special because they not only expand our knowledge of the past but also open a window to the different possibilities we can uncover.”
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