In over a decade and thousands of scientific models, this is the best yet.
I saw it in Nature and after observing Fig 1 innocently clicked the "corresponding author" button, all unaware that I was writing to a living legend. Dr Inoue founded the field of cytoskeleton dynamics (how structures move within cells, e.g. during mitosis), and if that weren't enough also video microscopy. He has very kindly shared this extraordinary data.
The species here is Damesites damesi, dating from the Cretaceious (some 70-85Mya), about 5cm in diameter, not common but not singular about 10 have been found. Like many ammonites it was a fast-moving free-swimming carnivore, perhaps most like today's chambered nautiluses, but not really like any modern animal. The crenellations in those chambers are nothing like any shell now, and the body that formed them must have been just as strange.
Ammonites are very common fossils (before fish grew jaws, they ruled the seas) and people have wondered forever what those wiggly lines meant in terms of 3D structure. Now, with X-ray tomography, we see.
Too small? The Mega Ammonite awaits.
Laser etched glass
90 x 90 x 45mm