This glorious discoidal darling is Mene rhombea, an extinct moonfish from the legendary Monte Bolca deposits of northeastern Italy.
She lived during the Mid-Eocene, roughly 45–50 million years ago, at a time when the world was warmer, crocodiles lounged much farther north, and lush tropical seas covered parts of Europe.
And what a slab it is.
The limestone matrix from Monte Bolca is world-famous for preserving fish with extraordinary fidelity. Bones, fin rays, eye sockets, delicate spines — all frozen in exquisite detail like nature’s own lithographic masterpiece.
You can see the elegant curve of the spinal column, the sharply compressed body, and those wonderfully dramatic pelvic fins trailing beneath like ribbons on a ballroom gown. If fish held fashion week during the Eocene, Mene rhombea would have strutted the runway in Milan and stolen everyone’s espresso.
Modern moonfish — relatives within the family Menidae — still swim in tropical Indo-Pacific waters today, though they are nowhere near as flamboyant as some of their fossil cousins.
The living species, Mene maculata, has the same deep, compressed body shape that lets it pivot and glide through reefs with remarkable agility. Their fossil kin tell us this lineage has been around for quite some time.
The family Menidae first appears in the fossil record during the Paleocene and flourished through the Eocene. Their fossils are known from Europe, Asia, and parts of North America, but nowhere are they more spectacularly preserved than at Monte Bolca.
This locality is one of the great Lagerstätten of the world — a fossil site with exceptional preservation — preserving a tropical marine ecosystem shortly after the extinction of the non-avian dinosaurs.
Monte Bolca itself is something of a celebrity in palaeontology circles. For over four centuries, collectors and scientists have marvelled at its fossil fishes. The deposits formed in quiet lagoonal waters associated with ancient coral reefs.
Fine carbonate mud settled gently to the seafloor, rapidly burying organisms in low-oxygen conditions that discouraged scavengers and decay. The result? Fossils so detailed you half expect them to blink.
Mene rhombea is instantly recognizable by its highly compressed, almost circular body shape and broad triangular tail. That shape was no accident. Like many reef-associated fishes, this body plan allowed quick manoeuvring through tight underwater spaces — handy when weaving through coral heads while trying not to become lunch for some enthusiastic Eocene predator with teeth the size of butter knives.
What I love most about these fossils is how modern they feel.
We often imagine prehistoric life as strange, lumbering, and alien, but many Eocene fishes would look perfectly at home in today’s tropical seas.
Standing before this fossil in Frankfurt, you are peering into an ocean only slightly different from our own — one filled with reef fish, rays, crustaceans, sharks, and the bustling energy of marine ecosystems recovering and diversifying after the great extinction at the end of the Cretaceous.
And here she remains.
Forty-five million years later, pressed delicately into limestone, elegant, dramatic, still the prettiest fish in the room