Chondrenchelyida

Chondrenchelyida is an extinct order of chimaeroid fish that lived during the Carboniferous and Permian periods. These cartilaginous fish are known from fossilized remains found in various locations worldwide, particularly in marine sedimentary rocks. Chimaeroids, also known as ghost sharks or ratfish, are cartilaginous fish related to sharks and rays, distinguished by their unique anatomical features.

Fossils attributed to Chondrenchelyida exhibit characteristics typical of chimaeroids, including a single gill opening on each side of the head, covered by a fleshy operculum. They possessed a fused dental plate in the upper jaw and a separate, movable lower jaw, which aided in crushing and grinding their prey. Many chondrenchelyids are believed to have been bottom-dwellers, feeding on invertebrates such as mollusks and crustaceans.

The taxonomic placement of Chondrenchelyida within the Chondrichthyes (cartilaginous fishes) is well-established, though its precise evolutionary relationships to other chimaeroid groups are still a subject of ongoing research. The limited fossil record for some species makes detailed reconstruction of their biology and ecology challenging. However, the study of Chondrenchelyida contributes significantly to our understanding of the early evolution and diversification of chimaeroid fish within ancient marine ecosystems.