 Compared to archaeocetes, primitive whales, the snout is wider, which may have been a precursor to the large mouths of modern baleen whales.Like other baleen whales, "Janjucetus" did not possess the ability to echolocate; however, it may have had a large line of fat along its lower jaw, similar to modern toothed whales (Odontoceti), which would mean it could detect ultrasonic signals.It had unusually large eyes for baleen whales compared to its body size, which were positioned high up on the skull; likewise, it probably relied on good eyesight instead of echolocation to navigate.