Pivot joint in rotating an arm inward). When rotating the forearm, these movements are typically called pronation and supination. In the standard anatomical position, the forearms are supinated, which means that the palms are facing forward, and the thumbs are pointing away from the body. In contrast, a forearm in pronation would have the palm facing backward and the thumb would be closer to the body, pointing medially. Examples of a pivot joint include: In contrast, spherical joints (or ball and socket joints) such as the hip joint permit rotation and all other directional movement, while pivot joints only permit rotation. Pivot
Bell's hinge-back tortoise Bell's hinge-back tortoise Bell's hinge-back tortoise ("Kinixys belliana") is a species of African tortoise, from the family Testudinidae. It has the hinge that characterizes all tortoises in the genus "Kinixys". There are several subspecies (some of which may actually be separate species; see below) and the Bell's hinge-back tortoise is subject to wide variation throughout its extensive range. Both the specific name, "belliana", and the common name are in honor of English zoologist Thomas Bell. Bell's hinge-back tortoise is a medium-sized light brown tortoise. They can grow up to 22 cm. On the back of its shell, the tortoise has