Gemuendina stuertzi (named for Gemünden from where it was discovered)[1] is a placoderm of the order Rhenanida, of the seas of Early Devonian Germany.

G. stuertzi is often invoked as an example of convergent evolution- with its flat body and huge, wing-like pectoral fins it has a strong, albeit superficial similarity to rays.

Unlike most other placoderm orders, such as the antiarchs or arthrodires, Gemuendina and its four other known relatives (or seven, if the three species of the ichthyolith genus Ohioaspis are confirmed to be rhenanids) had armor made up of a mosaic of unfused bony plates and scales.

Because several regions of the Hunsruck lagerstätte were anoxic, thus free of scavenging organisms, intact, nearly pristine (albeit flattened) specimens of G. stuertzi have been found as a result.

Instead, it had star-shaped tubercle scales that allowed it to seize, then swallow fish and other animals that swam too close with its mouth.