Cowralepis mclachlani
Late Middle Devonian
Merriganowry Shale
Cowra, New South Wales, Australia

80mm placoderm on 90mm slab.

Cowralepis belongs the extinct Class Placodermi, a group of diverse armored fishes that ruled the Devonian seas.  This genus is known from well-preserved specimens including the gill arches and tail at various growth stages so researchers have been able to study its path of development into adulthood as well as the evolution of early jawed vertebrates in general.  This is unusual because most placoderms are known from jaws or head and trunk shields sometimes found together but little to nothing of the branchial skeleton.