The Rajidae family is the most diverse group of rays. These benthic cartilaginous fishes are characterized by a flattened, diamond-shaped body, broad pectoral fins fused to the head and a relatively thin tail that typically has two dorsal fins. They are primarily marine and inhabit sandy or muddy bottoms from coastal areas down to great depths, where they feed on small fish, crustaceans and mollusks. Being oviparous, they lay eggs protected by a hard capsule, often called a "mermaid's purse". Due to their slow growth, late sexual maturity and low reproductive rate, many species are vulnerable to overfishing and bycatch.