The Astropecten articulatus, more commonly known as the royal starfish, is a West Atlantic sea star of the family Astropectinidae.

Description The Royal Starfish is characterized by its bold colors. It has a purple granulated disk, which is the central region of the sea star, and the purple color continues to extend to its five arms. The margin of the sea star, which is its outline, is an orange color. Entomologist Thomas Say describes the sea star's margin as “articulated throughout”, meaning that the orange margin that surrounds the sea star is continuous, even at the joints of its rays. It also has white spines that are attached to the orange margin and tube feet at the ends of its rays. The tube feet are cylindrical with conical ends, and the epithelium of the tube foot is covered by a thin layer of cuticle. Underneath the epithelium is the nervous tissue, and underneath that are fibrous tissues in the form of both left and right helices which protect the sea star's muscle tissue layer. The tube feet also contain bilobed ampulla. The ampulla muscle layers in the tube feet allow for the tube feet to elongate and shorten, which allows the sea star to move.