antiarchs

Antiarchs were a group of heavily armored, jawless fish that lived during the Silurian and Devonian periods. They belong to the extinct class Placodermi, which were among the earliest jawed vertebrates. A defining characteristic of antiarchs was their fused, box-like head shield and a flexible body covered in scales. Their most distinctive feature, however, was the presence of paired, segmented pectoral fins that were rigid and articulated, resembling limbs. These fins were typically held close to the body and were not used for active swimming in the way modern fins are.

The exact function of these specialized pectoral appendages is still debated among paleontologists. Theories suggest they might have been used for probing the seabed, for support while resting on the bottom, or possibly for maneuvering in shallow, complex environments. Antiarchs were bottom-dwellers and likely fed on small invertebrates and detritus found on the seafloor. Their armor provided significant protection against predators, which were becoming more diverse during the Devonian. Notable antiarch genera include Bothriolepis and Dickinsonia. The group became extinct by the end of the Devonian period, possibly due to competition from more advanced fish groups or changes in marine ecosystems.