Two small, oval fossils thought to be prehistoric plants are actually the remains of baby sea turtles, researchers have revealed.
The fossils, found in rocks dating between 132 and 113 million years ago, were discovered in Colombia in the mid-20th century by Padre Gustavo Huerta, a priest with a penchant for fossil plants.
Initially, the fossils were thought to represent a species of sphenophyllum – an extinct plant related to modern “horsetails” – with leaves divided into wedge shapes and veins radiating from their bases. But experts now say that was a mistake.
“During the re-examination of the fossils we tried to find the veins of leaves. However, what we observed was a delicate layer of spongy bone tissue, which led us to rule out the possibility that these fossils came from plants,” says Prof Edwin Cadena, a co-author of the study from the Universidad del Rosario in Bogotá.
“Instead, we started comparing them to vertebrate fossils, and images of hatchling turtles immediately came to mind.”
Write in the journal Palaeontologia Electronicareport the team how they compared the fossils with specimens of living sea turtles, as well as fossils of another species of sphenophyllum.
The team says the revealed oval fossils – which are 5cm and 6cm long – are actually the hard shells, or carapaces, of sea turtles. What were originally thought to be the veins of leaves are actually bone growth patterns, they note, while there is also evidence of bones within the shell called neurals and costums, as well as highly toothed joints between them.
The researchers say the turtles were probably less than a year old, and possibly of the species Desmatochelys padillai It was a type of protostegid, a group of extinct sea turtles that includes some of the largest ever to have lived.
However, in a nod to the early misidentification, the team nicknamed them “Turtle,” after a Pokemon character who is half turtle and half plant.
Dr Nick Fraser, an expert in vertebrate palaeontology at National Museums Scotland, who was not involved in the study, said the new interpretation made much more sense, as sphenophyllum existed in the Paleozoic era, while the deposits in which the fossils found date to the later Mesozoic era – a discrepancy that Cadena said is similar to the erroneous suggestion that dinosaurs lived at the same time as mammoths.
Fraser added: “In some ways the new interpretation is no less important and their identity as hatchling turtles seems spot on to me. Such early-stage turtles are rare in the fossil record and additional study, including CT analysis, may reveal valuable information that may allow species [identification].”
Prof Andy Gale, a geologist and palaeontologist at the University of Portsmouth, said he was “absolutely certain” the specimens were turtle hatchlings rather than a plant. “An unusual misidentification, showing that sometimes you see what you want to see, even though it’s not there,” he said.
