Nalumimidae

Nalumimidae is a family of extinct cartilaginous fishes, commonly referred to as "chimaeras". These prehistoric relatives of modern chimaeras lived during the Mesozoic Era, primarily the Jurassic and Cretaceous periods. Fossil remains of Nalumimidae are found in various marine deposits worldwide, offering insights into their ancient distribution and evolution.

Members of Nalumimidae possessed a cartilaginous skeleton, characteristic of chondrichthyans. Their body shape was typically fusiform, adapted for aquatic locomotion. They had large, often forward-facing eyes, suggesting they were visual predators. A prominent feature was their elongated rostrum, or snout, which varied in shape and size among different species. This rostrum may have served sensory, defensive, or even display functions. Their teeth were adapted for crushing and grinding, indicating a diet of hard-shelled invertebrates such as mollusks and crustaceans.

The evolutionary history of Nalumimidae is part of the broader diversification of cartilaginous fishes. While their exact phylogenetic placement within the Holocephali (the group that includes modern chimaeras) is still debated, they represent an important lineage that flourished before being largely replaced by other groups. The extinction of Nalumimidae likely occurred during the Cretaceous-Paleogene extinction event or shortly thereafter, marking the end of their distinct evolutionary path. Studying Nalumimidae fossils helps paleontologists understand the development of early chimaeras and the paleoecology of Mesozoic marine environments.