Earliest heart

The earliest known heart dates back 380 million years, to the late Devonian Period, and was discovered preserved inside a fossilized specimen of Mcnamaraspis kaprios, a species of ancient placoderm fish also known as the Gogo fish, named after the Gogo rock formation in Western Australia where it had been disinterred. This extraordinary discovery was publicly announced in September 2022, revealing that an exceedingly rare mineralization occurrence had preserved many of the fish's soft internal organs intact in their original 3D form, including not only its heart but also its bilobed liver, stomach and intestine. The heart was found via 3D scanning to be quite complex and advanced in structure, containing two discrete chambers.

Also known as plated fishes on account of their often very pronounced head and thorax armour, consisting of thick plates, placoderms were among the earliest jawed fishes, and included some of the most formidable marine predators of their time, culminating in the mighty 8.8-m-long Dunkleosteus. They constituted an entirely separate taxonomic class from all other fishes, one that is now long-extinct –placoderms –existing from the Silurian Period to the Late Devonian, approximately 430–360 million years ago.