Most vertebrates go to any length necessary to protect their vital spinal cord. The barbled dragonfish is not that concerned, and has dispensed with continuous neck bones as a tradeoff for eating bigger prey. A study by Nalani Schnell and David Johnson described the small but scary-looking fish's anatomy as having a gap between the neck and head where no bone restricts its head movement.
Now, to add to the freak show, it appears some barbeled dragonfish have a rather freestyle connection between their head and their body—one that allows them to achieve a 120 degree wide, banshee-like mouth gape.
“We certainly know of no other fishes with this feature,” Johnson told Gizmodo. Most vertebrates have bone-to-bone joints between the head and the neck, including us, he added.
The discovery came about through Schnell’s dissertation work, which focused on the peculiar anatomy of the barbeled dragonfish’s upper vertebra. Her early research showed that these creatures have a “flexible gap” between the occipital bones at the base of the skull, and the first ossified vertebra of the neck. Within this flex region, notochord tissue—a cartilage-like material that runs through the spines of all vertebrates—lacks the typical bony outer casing.
The fish is apparently unaware of how easy a spinal cord can snap. But since it lives in the deep and can withstand pressures we cannot, it's a safe bet to say that the marbled dragonfish is pretty tough. Read more about the research at Gizmodo.