On Wednesday, Peruvian researchers lifted a protective covering in a Lima laboratory and revealed the fossilized skeleton of Lomacetus, a marine dolphin that lived about 12 million years ago. The nearly complete specimen measured 3.5 metres from rostrum to tail and was unearthed in July by Peruvian paleontologist Mario Urbina in the Ocucaje Desert, about 350 kilometres south of Lima, reported the Straits Times.
The Ocucaje Desert, often labeled a great hotel for marine animals because of calm conditions that once prevailed there, has long served as a cemetery for ancient species. Coastal mountains shielded the area from strong currents, creating an ideal reproduction zone, Urbina said. Over more than two decades, scientists documented skeletons of four-legged dwarf whales, dolphins, sharks and other Miocene creatures in the same expanse. The region lay under sea for roughly 45 million years, a stretch that preserved fossils and offered researchers a window into how the Peruvian coastline shifted over millennia.
Lomacetus was preserved in near-perfect condition. “We have a practically intact skeleton, which will allow us to reconstruct how it moved, what it ate, or how long it could live,” said Mario Gamarra, a paleontologist at Peru’s Geological, Mining and Metallurgical Institute (Ingemmet), according to Phys.org. By examining the articulated spine, flippers and elongated skull, specialists planned to study propulsion, diet and age markers such as tooth-wear patterns or growth rings.
Although Lomacetus swam in the open Pacific, it shared traits with today’s porpoises, known locally as sea pigs, that still frequent Peru’s coastal upwelling zones, Gamarra added. The similarity intensified interest in the fossil’s flipper structure and vertebral column, which could clarify how modern porpoises evolved compact bodies and rapid tail beats.
The Pisco geological formation, which includes Ocucaje, preserved numerous articulated skeletons because fine sediments settled quickly over carcasses before scavengers arrived. Researchers from Ingemmet said each new discovery in Pisco sharpened the map of ancient shorelines, revealing where bays once opened and where cliffs later emerged as the Andes rose.
Lomacetus followed other Miocene finds. In April 2024, specialists displayed the fossilised skull of the largest river dolphin ever recorded, a species that patrolled Amazonian waterways around 16 million years ago. Earlier in 2024, scientists recovered a nine-million-year-old fossil belonging to a relative of the great white shark, extending knowledge of apex predators that once cruised the same coastal corridor. Discoveries far inland confirmed that the uplift of the continent scattered marine deposits across Peru.
Excavation in Ocucaje proceeded with hand tools to protect fragile bones, while laboratory preparation in Lima involved consolidating vertebrae with resin and cleaning silt from cranial cavities. Researchers planned to create 3-D scans before taking intrusive samples. Chemical analysis could reveal details about Lomacetus’s diet by matching isotopes preserved in teeth to those in fish and squid that inhabited the Miocene Pacific. If growth layers on ribs and vertebrae could be counted, scientists might estimate lifespan and seasonal migration patterns.
Ingemmet intended to display the specimen publicly after conservation work concluded. The skeleton would join an exhibition that already included dwarf whale fossils with vestigial hind limbs and a wide range of Miocene sharks. Ocucaje is a true treasure for world paleontology, wrote La Vanguardia, noting that the desert preserves marine life at multiple stages of evolution.
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