Climatius

Climatius (from κλίμα, 'gradation') is an extinct genus of spiny shark. This genus is known from the Early Devonian (Lochkovian) of Europe, previously considered Silurian remains actually belong to Nostolepis instead.

Climatius was an active swimmer, judging from its powerful caudal fin and abundant stabilizing fins, and probably preyed on other fish and crustaceans. Its lower jaw was lined with sharp teeth which were replaced when worn, but the upper jaw had no teeth. It had large eyes, suggesting that it hunted by sight.

Climatius represents an important evolutionary link in understanding early jawed vertebrates. Its distinct features, such as double-layered globular calcified cartilage and specialized dental structures, offer crucial insights into the morphological diversification and adaptive strategies of Devonian fish.

It was a small fish, at 7.5 cm, and to discourage predators, Climatius sported fifteen sharp spines. There was one spine each on the paired pelvic and pectoral fins, and on the aingle anal and two dorsal fins, and a four pairs without fins on the fish's underside.