The arrangement and relative strength of the muscles suggests ammonites swam by expelling water through their hyponomes, found next to the opening to the body chamber.

From this detailed model, they were able to infer the functions of the muscles and organs. They looked at the fossilРІР‚в„ўs remaining soft tissues and scarring where muscles once attached to the inside of its shell.Р”В«y combining high-resolution X-ray and high-contrast neutron imaging, they created a detailed 3D computer reconstruction of the structure, size, and orientation of its muscles and organs. To carry out the study, the researchers studied the five-centimeters-across ammonite fossil that was found within an exposed Jurassic sediment at a Gloucestershire site in 1998. Thus, ammonite fossils with preserved muscles and organs are extremely rare. They are among the most common fossils worldwide, but almost everything we know about them so far is based on their hard shells as these are more easily preserved over millennia than bodily tissues. This is a major breakthrough in ammonite paleobiology.РІР‚Сњ Squid-like propulsionР”Р„mmonites, which became extinct around 66 million years ago, once thrived in oceans as dinosaurs ruled the Earth. New imaging techniques allowed us to visualize the internal soft parts of ammonites that have so far resisted all our previous efforts to describe them. Alan Spencer, from ImperialРІР‚в„ўs Department of Earth Science and Engineering and the Natural History Museum, said: РІР‚СљThis ammonite is remarkably well preserved, which is very rare. The findings add insight into how ammonites lived and provide evidence that coleoids, the sub-group of animals containing squid, octopuses, and cuttlefish, might be evolutionarily closer to ammonites than previously thought.

The research, published today in Geology, marks the first time an ammoniteРІР‚в„ўs softer parts have been visualized in three dimensions-and is thanks to a combination of modern technology, the fossilРІР‚в„ўs exceptional preservation, and collaboration across interdisciplinary teams and facilities. The team, including researchers from Cardiff University and Imperial College London, found this by analyzing the muscles and organs of an exceptionally well-preserved ammonite fossil found over 20 years ago in Gloucestershire, UK. They also found strong muscles that ammonites used to retract into their shells to defend against predators. They found that the now-extinct molluscs sported hyponomes: tube-like syphons through which water is expelled to jet propel animals forward in water, as found in modern squid and octopuses. For the first time, researchers have revealed the soft tissues of a 165-million-year-old ammonite fossil using 3D imaging.

Leica microscope