Æxliformes

Æxliformes is a hypothetical order of extinct cartilaginous fish that existed during the Carboniferous period. While the exact classification and relationships of Æxliformes are debated among paleontologists, they are generally considered to be a group of basal chondrichthyans, meaning they are early relatives of modern sharks and rays.

Fossil evidence for Æxliformes is sparse, primarily consisting of isolated teeth, dermal denticles, and sometimes poorly preserved skeletal remains. These fossils suggest that Æxliformes possessed relatively robust jaws and a diet that likely included invertebrates and possibly smaller fish. Their body shape and fin arrangements are not well understood due to the limited fossil material.

The significance of Æxliformes lies in their potential to illuminate the early evolution of cartilaginous fishes. By studying their morphology and phylogenetic placement, scientists hope to better understand the diversification of chondrichthyans during the Paleozoic Era, a crucial period for the development of many vertebrate lineages. The group remains an active area of research, with new discoveries potentially reshaping our understanding of these ancient fish.