Aggrekaniformes

Aggrekaniformes is an extinct order of bony fish that lived during the Devonian period. These fish are characterized by their large size and a distinctive pattern of bony plates covering their bodies. They are considered to be among the earliest ancestors of modern ray-finned fishes, though their exact evolutionary relationships are still debated.

The most prominent feature of Aggrekaniformes is their extensive cranial and postcranial armor. This bony covering provided significant protection but likely also contributed to their limited mobility. Their jaws were relatively small, suggesting a diet of small invertebrates or detritus. Fossil evidence indicates that Aggrekaniformes inhabited freshwater environments, such as lakes and rivers, in what is now North America and Europe.

The classification of Aggrekaniformes within the broader context of fish evolution has been a subject of ongoing research. While once placed in a more basal position among teleosts, recent phylogenetic analyses suggest they may be more closely related to certain early actinopterygian groups. The extinction of Aggrekaniformes by the end of the Devonian is thought to be due to a combination of factors, including environmental changes and competition from more adaptable fish groups that emerged during the Carboniferous period. Their fossils provide valuable insights into the diversity and early evolution of bony fishes.