Prehistoric whale fossil reveals record level of facial asymmetry

An international research team identified a new extinct species of pygmy sperm whale called Scaphokogia huachafo from the Late Miocene period.

The team studied a fossil skull found in the Pisco Formation in southern Peru, a region known for preserving marine fossils in desert outcrops. The whale lived between 6.3 and 5.6 million years ago and reached a length of approximately 2.7 meters.

The researchers found that this whale possessed the most extreme facial asymmetry ever recorded in any cetacean, a group of marine mammals that includes whales and dolphins. While most mammals have symmetrical heads, toothed whales develop asymmetrical skulls to house organs for sound production. In this specific species, the asymmetry was so severe that both bony nostrils shifted entirely to the left side of the head, and the facial bones varied greatly in size and position.

The team determined that the whale was a specialized bottom feeder in shallow coastal waters. Its snout formed a thick, tubular structure reinforced with dense bone and cartilage to act as ballast, shifting the animal's center of gravity downward. The snout angled down by 31 degrees, and the neck joint allowed the whale to bend its head downward by up to 55 degrees.

Scientists believe the whale used its asymmetrical biosonar to scan the seabed for prey before these coastal ecosystems disappeared at the end of the Miocene.