Plant fossil turns out to be 100-million-year-old baby turtle

Between the 1950s and 1970s, Colombian priest Padre Gustavo Huertas collected what he believed to be plant fossils near Villa de Leyva. Specifically, two small, round rocks with leaf-like patterns were classified as Sphenophyllum colombianum, a fossilized plant, in 2003. However, a recent study published in Palaeontologia Electronica reveals a surprising twist—these specimens are not plants but the fossilized remains of baby turtles.

Héctor Palma-Castro, a paleobotany student at the Universidad Nacional de Colombia, expressed his surprise at the discovery, highlighting the unexpected nature of these fossils. The initial classification as Sphenophyllum colombianum was made due to their appearance and the fact that they came from Early Cretaceous rocks dating between 132 and 113 million years ago.

The interest in these fossils grew when Fabiany Herrera, the Negaunee assistant curator of fossil plants at the Field Museum in Chicago, and his student Palma-Castro started examining them. Herrera, who has been collecting Early Cretaceous plants in northwestern South America, noticed peculiar features that didn’t align with typical plant characteristics.

The fossils, approximately 2 inches in diameter, initially resembled rounded nodules with preserved Sphenophyllum leaves. However, closer inspection revealed discrepancies, leading them to question the original classification. Palma-Castro emphasized the challenges in deciphering the shape and margin of the supposed plant leaves.

Upon close examination, Herrera noticed that the lines on the fossils didn’t resemble plant veins but rather suggested bone structures. Seeking further expertise, Herrera consulted with Edwin-Alberto Cadena, a paleontologist at the Universidad del Rosario in Bogotá, specializing in turtles and vertebrates.

Cadena, upon reviewing the photos, recognized the fossil as a turtle carapace, the bony upper shell. Notably, it turned out to be a hatchling specimen, exceptionally small in size. The revelation challenges the initial classification and adds an intriguing layer to the understanding of fossils collected by Padre Gustavo Huertas decades ago.

Drawing highlighting the rib and back bones, superimposed onto the fossil. Credit: Fabiany Herrera and Héctor Palma-Castro; drawing by Edwin-Alberto Cadena and Diego Cómbita-Romero.

Cadena and Diego Cómbita-Romero from the Universidad Nacional de Colombia conducted further examinations of the specimens, comparing them with both fossilized and modern turtle shells.

“When we saw the specimen for the first time, I was astonished because the fossil lacked the typical marks on the outside of a turtle’s shell,” says Cómbita-Romero. “It was a little bit concave, like a bowl. At that moment, we realized that the visible part of the fossil was the other side of the carapace; we were looking at the part of the shell that is inside the turtle.”

Details in the turtle’s bones allowed the researchers to estimate its age at death. Examining features such as the thickness of its carapace and the fusion points of its ribs helped determine that the turtle likely died between 0 to 1 years old, in a post-hatchling stage.

Discovering hatchlings of fossil turtles is rare due to the fragility of their thin bones when very young. Cadena notes the rarity of such findings, emphasizing the importance of this discovery. The researchers named the specimens “Turtwig,” drawing inspiration from a Pokémon that combines turtle and plant elements.

“In paleontology, your imagination and capacity to be amazed are always put to the test. Discoveries like these are truly special because they not only expand our knowledge about the past but also open a window to the diverse possibilities of what we can uncover,” says Palma-Castro.

The researchers acknowledge Padre Gustavo Huertas’ initial classification, attributing the mistake to the uncanny resemblance of the preserved shells to fossilized plants. They highlight the significance of re-examining historical collections in Colombia, emphasizing the critical period of Early Cretaceous land plant evolution and expressing their commitment to uncovering the forests that thrived in this region during that time.

Source: Field Museum

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