Scientists have uncovered a vast graveyard of ancient marine reptiles hidden under a glacier in southern Chile.

In a new study published in the Geological Society of America Bulletin, the researchers document the discovery of the remains of 46 ophthalmosaurid ichthyosaurs (marine reptiles) at the Tyndall Glacier in the Torres del Paine National Park of southern Chile.

Four different species were identified with the remains very well preserved, and some including soft tissue and embryos.

The “unique” discovery was dated to the Early Cretaceous period, about 146 million years ago, and should help scientists determine how and why the species found eventually became extinct.

In a statement, the researchers said:

The Tyndall ichthyosaurs were gregarious and likely hunted in packs in a submarine canyon near the east coast of this sea. Their potential prey, belemnites and small fishes, were abundant due to plankton blooms caused by cold water upwelling. Occasionally, high energy turbiditic mudflows sucked down everything in their reach, including ichthyosaurs. Inside the suspension flows, the air-breathing reptiles lost orientation and finally drowned. They were instantly buried in the abyss at the bottom of the canyon.