A study, published in the Journal of Vertebrate Paleontology, offers a detailed description of a fossil of a pregnant ichthyosaur named Fiona, approximately 131 million years old, discovered in Chilean Patagonia.
The fossil remains of Fiona were recovered at the edge of the Tyndall Glacier in Torres del Paine National Park, an area that became accessible due to the retreat of glaciers caused by global warming. "These climatic processes that reveal these treasures are the same ones that threaten to destroy them," noted Dr. Judith Pardo, the lead author of the research from the Universidad de Magallanes (UMAG).
Fiona is the first complete ichthyosaur specimen excavated in Chile and the only known pregnant ichthyosaur from the Hauterivian age, approximately 131 million years ago, according to La Tercera. "At this site, in addition to Fiona, we have recorded 87 ichthyosaurs, most of which are complete and articulated. This site currently preserves the largest number of Hauterivian ichthyosaurs on the planet," said Dr. Pardo, as reported by La República.
Despite their resemblance to dolphins, ichthyosaurs are not related to these marine mammals. They shared a similar body plan with two front flippers, two hind flippers, a dorsal fin, and a tail fin for propulsion in water. Like all reptiles, ichthyosaurs breathed air and periodically had to swim to the surface to breathe through their nostrils. Their adaptation to aquatic life was so profound that, instead of laying eggs like other reptiles, they gave birth to live young in the water.
The excellent state of preservation of Fiona's skeleton allowed researchers to obtain invaluable information about her anatomy, reproductive biology, and ecology. Fossilized remains of fish were found in Fiona's belly, providing evidence about her diet, as noted by BioBioChile. Additionally, one of Fiona's flippers shows an unusual pathology, possibly caused by an injury during swimming, suggesting that the animal may have suffered an injury or disease. "Paleopathologies in Cretaceous ichthyosaurs are extremely unusual, so this finding is of great value for understanding the health and physiology of these marine reptiles," said Pardo.
The fetus, measuring around 50 centimeters, was positioned in a way that indicates it was in the final stages of prenatal development, suggesting it was possibly ready to be born. This provides researchers with insights into the reproductive biology of ichthyosaurs, marine reptiles that inhabited Earth from the Early Triassic to the Late Cretaceous, approximately 250 to 93 million years ago. Fossils of ichthyosaurs have been found in parts of the world, but they are better known in the Northern Hemisphere, while in the Southern Hemisphere, their fossils are much less known.
The Tyndall Glacier area has been described as a "graveyard of sea dragons" by some paleontologists due to the large number of similar finds. "Nearly 100 skeletons have been found in this remote region, including adults, juveniles, and newborns," said Dr. Dean Lomax. The site has become important for understanding ichthyosaur diversity and distribution during the Cretaceous period.
The rescue of Fiona was documented for a forthcoming audiovisual work to highlight the importance of the site and the research team's efforts. "Fiona is not just a fossil; she is a symbol of identity that fosters conservation and awakens curiosity in children, young people, and adults," said Pardo. The fossil remains are currently housed at the Río Seco Natural History Museum in Punta Arenas, Chile.
"Fiona provides an unprecedented insight into the life and death of ichthyosaurs in a period from which we have very few records," said Dr. Erin Maxwell, co-author and curator of marine reptiles at the State Museum of Natural History in Stuttgart, Germany. "The excavation of this specimen in challenging terrain and under extreme conditions is an exceptional achievement," she added.
The discovery of Fiona helps fill a gap of about 70 million years in the fossil record of this species. It offers new information about the ichthyosaur species that inhabited Earth millions of years ago, including insights into their paleobiology, paleoecology, anatomy, and reproductive biology.
The article was written with the assistance of a news analysis system.