Marine species include some of the most hydrodynamically shaped creatures on Earth, which figures when you consider Darwin’s theory of natural selection likely favored animals that were good at chasing after or escaping prey/predators in the water. It’s perhaps then difficult to imagine how an animal shaped like a giant paperclip came to be but that’s exactly what was swimming around in the ocean in the late Cretaceous.
Diplomoceras maximum, a squid-like creature with a spiral calcified shell à la Microsoft's Clippy, lived around 68 million years ago. It was about 1.5-meters (5 feet) in length and was a member of a class of tentacled cephalopods commonly known as ammonites. While much remains a mystery about these strangely shaped sea creatures, new research announced at an online meeting of the Geological Society of America has uncovered new evidence that they had a very long life expectancy.
Linda Ivany at Syracuse University, New York, and colleague Emily Artruc were investigating chemical signatures in specimens of D. maximum when they made the discovery. Testing samples of a fossil, they focused on the carbon and oxygen isotopes along a 50-centimeter (almost 20-inch) section of shell, which revealed a repeating pattern in its isotopic signatures. The researchers interpret this as a translation of the annual release of methane from the seafloor, which is expelled by microbes that break down organic matter.
Ivany and Artruc recognized that these signatures aligned with ridges along the stretch of the shell, which indicate that each shell ridge represents a year much like the rings inside the trunk of a tree. Their assumption fits as shells are known to grow by accretion, laying down new growth each year. After scaling up the enormous shells of these 1.5-meter-long animals, they concluded that the only logical interpretation was that these animals had a life expectancy of around 200 years.
Extant species of cephalopods are short-lived, clocking just a few years. Nautiluses last a few decades and some shellfish can last a few centuries, but D. maximum was a cephalopod, making its mighty age something of a surprise. It’s possible its long life may have been attributable to its environment, as these animals lived around Antarctica where the water would have been cold and food would have been sparse. A slow metabolism would’ve supported life under such conditions, which is a physiological feature associated with longevity in animals such as the Greenland shark.
It’s too early to conclude how and why these creatures could survive for so long, but the revelation of their life expectancy has shone new light on the curious case of the Clippy-shaped ammonite that could open doors to better understanding their ecology. Shine on, you crazy paperclip.