A rare pod of orcas washed up dead on a beach in Chile. It's the first event of its kind in 67 years and only the second in recorded history.

• A rare pod of orcas washed up dead on a beach in Chile late last year, according to LiveScience.
• It was only the second time in recorded history the Type D orcas had been found stranded.

A rare pod of orcas washed up dead late last year. It's the first mass stranding of these killer whales in 67 years and only the second event of its kind in recorded history, according to LiveScience.

The orcas are of a rare subgroup called Type D, and are different from other killer whales due to their rounded head, distinctly smaller white eye patches, and curved dorsal fins.

Moreover, these orcas are not to be mistaken for the pod that is ramming boats, ripping off rudders, and sometimes sinking vessels, near the Strait of Gibraltar off the coast of south Spain — different locations, different types of killer whales.

Type D orcas were first discovered in 1955 when a group of 17 washed ashore off the coast of New Zealand. A similar event occurred late last year, where a total of nine Type D orcas washed ashore on the other side of the South Pacific Ocean on a beach in Chile.

"I have to admit, I never thought I would hear about another stranding of Type D killer whales in my lifetime," Robert Pitman, a marine ecologist at Oregon State University who has been studying Type D orcas for years, told LiveScience.

The first orca to wash ashore was a lone female that, upon autopsy, was a healthy adult with no signs of disease or human interference. This is unusual since orcas will sometimes beach themselves due to illness, leaving the reason for this mysterious and rare event unknown, per LiveScience.

The other eight orcas were much more decayed when they were discovered a few weeks later, per LiveScience.

Type D orcas have one of the highest levels of inbreeding of any mammal

Little is known about Type D orcas, since they tend to live in especially turbulent and rough seas in the Southern Pacific where few boats venture.

In 2019, Pitman led a team of scientists to the mysterious orcas' habitat, where he found a pod of 30 with a surprising genetic footprint.

Type D orcas show "among the highest level of inbreeding reported for any mammalian species," Pitman and his colleagues wrote in their findings, published in the Journal of Heredity in March.

Even though the Type D orcas lived and traveled in areas that overlapped with other types of orcas, they didn't seem to breed with them. The elusive Type D whales had an incredibly low level of genetic diversity.

The researchers found an almost identical genetic code between Type D orcas in Chile and the skeleton of a Type D that was beached in New Zealand. That "suggests inbreeding over many generations," Andrew Foote of the Norwegian Institute of Science and Technology, who led the study, said in a March press release.

In 2019, a video of the Type D orcas was published by National Oceanic and Atmospheric Administration, showing these rare creatures swimming off the coast of Chile.