Neoselachian

Neoselachian is a taxonomic infraclass of cartilaginous fish that includes all modern sharks, rays, and skates. This group is distinguished from their extinct relatives by several key anatomical features, including a calcified skeleton, a more complex jaw structure, and typically five to seven gill slits on each side of the head. The term "neoselachian" literally translates from Greek as "new shark."

The lineage of neoselachians diverged from other elasmobranchs during the Mesozoic Era. Their evolutionary success is attributed to a variety of adaptations, such as streamlined bodies for efficient swimming, advanced sensory systems including electroreception and a keen sense of smell, and diverse feeding strategies. Within this infraclass, the diversity of forms is remarkable, ranging from the large filter-feeding whale shark to the flattened, bottom-dwelling stingrays.

Neoselachians are found in all the world's oceans, inhabiting a wide spectrum of environments from shallow coastal waters to the deep sea. They play crucial roles in marine ecosystems as predators and, in some cases, as prey. Conservation efforts are increasingly focused on neoselachian populations due to threats such as overfishing, habitat degradation, and bycatch. Understanding the biology and ecology of these ancient yet modern fish is vital for their continued survival.