A fossilized skeleton of a rarely studied dolphin species dating back up to 12 million years has been unearthed in the Ocucaje Desert, shedding new light on the ancient marine history of southern Peru. The dolphin, identified as Lomacetus, measured approximately 11.5 feet in length and was found in July by a team of Peruvian paleontologists. The site, now a dry expanse of sand, once lay beneath the Pacific Ocean.
The discovery, announced on Sept. 17 by researchers from Peru's Geological, Mining and Metallurgical Institute, offers critical clues about the region's shifting coastline and long-lost marine ecosystems.
Lead geologist César Chacaltana said the fossil indicates that millions of years ago, the local climate, terrain, and shoreline were vastly different.
Geological forces and climate shifts have since transformed the former seabed into a desert, preserving remnants of marine life beneath layers of sand.
Lomacetus, part of the extinct Kentriodontidae family, lived during the Miocene epoch, which spanned from 23 to 5 million years ago. This family is considered a transitional group in the evolution of toothed whales.
Researchers noted the fossil shares traits with modern porpoises, which still inhabit Peruvian waters.
Although early specimens were first recorded in North America, this find suggests a broader range and raises new questions about the dolphin's migration and distribution across ancient oceans.
🐬 Paleontólogos presentaron en Perú el fósil de Lomacetus, un delfín marino de 12 millones de años hallado en el desierto de Ocucaje, a 350 km al sur de Lima.
⏳ Con 3.5 metros de longitud, el esqueleto fue encontrado casi completo y representa un hallazgo clave para el estudio... pic.twitter.com/d0Lv92sq5t
-- JaliscoTV (@JaliscoTV) September 18, 2025
The United States Geological Survey explained that the middle Miocene period -- between 15 and 11 million years ago -- was marked by warmer, more stable conditions. These changes supported a rich diversity of marine species, particularly in tropical zones like Peru.
Paleontologist Mario Gamarra said the well-preserved fossil allows researchers to study its movement, diet, and lifespan, providing deeper insight into how the species thrived in this once-vibrant sea.
Paleontologist Mario Urbina added that the region's geography, with coastal mountains running parallel to the sea, created favorable breeding grounds for marine animals during that era.
The Ocucaje Desert, part of the Pisco Formation, is regarded as one of the most important fossil sites in South America. It has yielded remains of ancient sharks, giant turtles, four-legged whales, and river dolphins.
In recent years, scientists have uncovered a 9-million-year-old relative of the great white shark and the skull of Pebanista yacuruna, the largest known river dolphin.
Together with Lomacetus, these finds help trace the transition from marine to freshwater species in South America.
Despite its scientific value, the site faces threats from fossil looting and uncontrolled development. A 2022 proposal to declare the area a protected paleontological zone remains under review.