Uncovering a baby turtle disguised as a plant fossil

The fossil was originally interpreted to be a plant, but researchers have now discovered it is the inside of a baby turtle’s shell. Photography: Fabiani Herrera and Hector Palma Castro

The researchers named the fossil “Turtwig” after the half-turtle, half-plant Pokémon.

From the 1950s to the 1970s, a Colombian priest named Padre Gustavo Huertas collected rocks and fossils near a town called Villa de Livia. Two of the specimens found were small round rocks decorated with leaf-like lines. He classified it as a type of fossil plant. But in a new study published in the journal Electronic fossilsThe researchers re-examined these “plant” fossils and found that they were not plants at all: but rather the fossilized remains of small turtles.

“It was really surprising to find these fossils,” says Hector Palma Castro, a paleobotany student at the National University of Colombia.

Huertas described the plants in question in 2003 as: Sphenophyllum columbianum. The fossils come from an early time Cretaceous period The rocks, between 132 and 113 million years ago, during the age of dinosaurs. excavations Sphenophyllum columbianum It was surprising at this time and place – other known members of the race Sphenophyllum He died more than 100 million years ago. The age and location of the plants intrigued Fabiani Herrera, assistant curator of fossil plants at the Field Museum in Chicago, and his student Palma Castro.

Wrong identity

“We went to the paleontological collection at the National University of Colombia in Bogotá and started looking at the plants, and once we photographed them, we thought, ‘This is strange,’” says Herrera, who has been collecting Early Cretaceous plants. From northwestern South America, a region of the world with few ancient botanical works.

At first glance, the fossils, about 2 inches in diameter, looked like round nodules containing preserved plant leaves. Sphenophyllum. But Herrera and Palma Castro noticed key features that were not quite right.

A drawing highlighting the rib and back bones, superimposed on the fossil. Credit: Photography by Fabiani Herrera and Hector Palma Castro; Painted by Edwin Alberto Cadena and Diego Competa Romero.

“We spent days searching in wooden cabinets for fossil plants. When we finally found this fossil, deciphering the shape and edges of the leaf was difficult,” says Palma-Castro.

“When you look at it in detail, the lines on the fossils don’t look like the veins of a plant, and I was sure it was probably bone,” Herrera says. So he reached out to an old colleague, Edwin Alberto Cadena.

“They sent me pictures, and I said, ‘This sure looks like a carapace’ — the bony upper shell of a turtle,” says Cadena, a paleontologist who focuses on turtles and other creatures. Vertebrates At the Universidad del Rosario in Bogotá. When he saw the size of the photos, Cadena recalls, “I said, ‘Well, this is great, because not only is this a turtle, but it’s also a very small specimen.’

Cadena and his student Diego Competa Romero of the National University of Colombia examined the samples and compared them to fossil and modern turtle shells. “When we first saw the specimen, I was amazed, because the fossil was missing the typical markings found on the outside of a turtle’s shell,” Competa-Romero says. It was a bit concave, like a bowl. At that moment we realized that the visible part of the fossil was the other side of the carapace, and we were looking at the part of the shell inside the turtle.

Details in the turtle’s bones helped researchers estimate its age at death. “Tortoises have different growth rates and sizes,” Competa-Romero says, so the team looked at features like the thickness of their carapace and the places where their ribs were fused together to form solid bones. “This is an uncommon trait in juvenile fish but is observed in juveniles. All this information suggests that the turtle may have died with a slightly developed carapace, between 0 and 1 year of age, at some post-hatching stage.”

The importance of discovery

“Finding fossil baby turtles in general is really rare,” Cadena says. “When turtles are very young, the bones in their shells are very thin, so they can be easily destroyed.”

The rarity of fossilized baby turtles makes their discovery important, researchers say. “These turtles are likely other Cretaceous relatives Classify “They were up to fifteen feet tall, but we don’t know much about how they actually grew to such gigantic sizes,” Cadena says.

The researchers don’t blame Padre Huertas for his mistake, as the preserved shells do indeed resemble many fossil plants. But the features that Huertas thought were leaves and stems are actually modified costal bones and vertebrae that make up the turtle’s shell. Competa Romero and Palma Castro named the specimens “Turtwig”, after a Pokémon that is half turtle and half plant.

“In the world of Pokemon, you encounter the concept of combining two or more elements, such as animals, machines, plants, etc. So, when you have a fossil initially classified as a plant that turns out to be a baby turtle, a few Pokemon immediately come to mind.” This case, Turtwig, a little turtle with a leaf attached to its head,” says Palma Castro. “In paleontology, your imagination and your ability to amaze are always tested. Such discoveries are truly special because they not only expand our knowledge of the past, but also open a window on diverse possibilities What we can discover.

Re-evaluation of historical collections

Scientists also point out the importance of these fossils in the broader scheme of Colombian paleontology. “We have solved a small mystery regarding ancient plants, but more importantly, this study shows the need to re-examine historical collections in Colombia. The Early Cretaceous is a critical time in the evolution of land plants, especially for flowering plants and gymnosperms,” says Herrera. “The future is to discover the forests that grow in this part of the world.”

Reference: “Sphenophyllum from the Early Cretaceous or a hatched turtle?” Written by Hector D. Palma Castro, and Diego A. Competa Romero, Edwin Alberto Cadena, Monica R. Carvalho, and Fabiani Herrera, December 2023, Electronic fossils.
doi: 10.26879/1306

This project was supported by the National Geographic Society Grant (EC-96755R-22) for the Discovery of Early Cretaceous Plants of Northern South America and the Negaune Integrative Research Center, The Field Museum.