“Turtwig”: the species of turtle that scientists thought was a plant

New research has revealed that ancient plant fossils that had puzzled scientists were actually not plants at all.

Instead, the small round shapes with a leaf-like pattern were once the shells of baby turtles that lived during the time of the dinosaurs. Scientists have nicknamed the turtle species “Turtwi,” after a Pokémon character that is half turtle, half plant.

The discovery marks the first time that baby turtle shells have been found in northwestern South America, according to the study authors.

The results of his research were published Thursday (7) in the journal Palaeontologia Electronica.

“In the Pokémon universe, you find the concept of combining two or more elements, such as animals, machines, plants, etc.,” said lead author Héctor Palma-Castro, a graduate student in paleobotany at the National University of Colombia, in a statement .

“So when you have a fossil initially 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 research to solve this paleontological mystery that began decades ago.

Wrong place, wrong time

It all started when the Colombian priest Father Gustavo Huertas discovered the fossils of the Paja Formation. The formation is part of one of Colombia’s geological heritages called Marine Reptile Lagerstätte de Ricaurte Alto.

Previous fossil discoveries at the site include dinosaurs, plesiosaurs, pliosaurs, ichthyosaurs, turtles and crocodile relatives called crocodylopmorphs, dating to 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, between the 1950s and 1970s. When he found the rocks with leaf patterns, he considered them to be a fossil plant. Huertas described the specimens as Sphenophyllum colombianum in a 2003 study.

Other scientists were surprised to learn that the plant was discovered in northern South America and dated to between 113 million and 132 million years ago. The now-extinct plant once existed throughout the world and died more than 100 million years ago, according to the fossil record.

Previous research on the plant showed that its leaves were typically wedge-shaped, with veins radiating 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 Field Museum of Natural History 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 where little paleobotanical research occurs.

Both fossils, measuring around 5 centimeters in diameter, were kept in collections at the geosciences department at the National University of Colombia. As they examined and photographed the fossils, Herrera and Palma-Castro thought something looked strange.

“When you look in detail, the lines seen in the fossils don’t look like the veins of a plant — I was sure it was probably bone,” Herrera, the study’s senior author, said in a statement.

Solving a fossil mystery

Herrera contacted his colleague Edwin-Alberto Cadena, a senior professor and paleontologist who studies turtles and other vertebrates at the Universidad Del Rosario 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, the study’s co-author, said in a statement.

“I said, ‘Well, that’s remarkable, because not only is it a turtle, but it’s also a baby specimen, it’s very, very small.’”

Cadena and one of his students, Diego Cómbita-Romero of the National University of Colombia, compared the fossils with the shells of other extinct and modern turtles.

“When we first saw the specimen I was surprised, because the fossil lacked the typical markings on the outside of a turtle’s shell,” study co-author Cómbita-Romero said in a statement.

“It was a little concave, like a bowl. At that moment we realized that the visible part of the fossil was the other side of the shell, we were looking at the part of the shell that is inside the turtle.”

During analysis of the shells, researchers determined that the turtles were at most 1 year old when they died.

As young turtles develop, their growth rates and sizes can vary, Cómbita-Romero said. But it’s rare to find remains of young turtles because the bones in their shells are so thin.

“These turtles were likely related to other Cretaceous species that were up to four and a half meters long, but we don’t know much about how they actually grew to such gigantic sizes,” Cadena said in a statement.

The researchers did not blame Huertas for miscategorizing the fossils as plants. What he believed to be leaves and stems were vertebrae and ribs inside a turtle’s shell.

“We have solved a small paleobotanical mystery, but most 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 next research team aims to discover the forests that once grew in the region, he said.

“In paleontology, imagination and the ability to be surprised are always put to the test,” said Palma-Castro. “Discoveries like these are truly special because they not only expand our knowledge about the past, but they also open a window into the many possibilities of what we can discover.”