Pleurotomaria

Pleurotomaria is an extinct genus of marine gastropod mollusks. These snails lived from the Triassic to the Eocene periods, meaning they were present for a significant portion of geological time. They are characterized by a distinctive slit or sinus on their shell, which is a key feature for identification. This slit was likely used for respiration or sensory purposes during the animal's life.

The shells of Pleurotomaria are typically conical or trochiform, often with a wide base and a pointed apex. They can exhibit various sculpturing patterns, including axial ribs and spiral cords, which vary greatly among different species. Many fossil specimens are found in marine sedimentary rocks from ancient seas and oceans.

Pleurotomaria belongs to the superfamily Pleurotomarioidea, a group of gastropods that are considered to be among the most primitive living gastropod families, though Pleurotomaria itself is entirely extinct. The living representatives of this superfamily, such as species in the genus *Haliotis* (abalone) and *Scissurella*, share some morphological similarities but are distinct from the fossil Pleurotomaria. The study of Pleurotomaria fossils provides valuable insights into the evolution of gastropods and the paleoenvironments in which they lived.