Radiale

Radiale refers to certain skeletal elements in the forelimb skeleton of vertebrates. The term is used in comparative anatomy and paleontology to describe two related concepts: a proximal carpal bone in the manus of many tetrapods, and a fin-support bone in the endoskeleton of fishes. Etymology: from Latin radialis, meaning “of the radius.”

In tetrapods: The radiale sits in the proximal row of carpal bones and typically articulates with the radius on its proximal face and with adjacent carpals or metacarpals distally. In many non-mammalian tetrapods, the proximal carpal row includes radiale, intermedium, and ulnare; in mammals the arrangement is reorganized and these elements are represented by bones such as the scaphoid and lunate, with the radiale term largely absent from standard human anatomy.

In fishes: In the fin skeleton of bony fishes and some early sarcopterygians, radiale is an endoskeletal element between the girdle and distal fin rays. It belongs to the series of radials and basalia that support the fin. The exact homology and terminology vary by lineage, and radiale may be equated with different bones in descriptive accounts.

Naming and usage: The term radiale is primarily encountered in paleontological descriptions and comparative anatomy. In modern human anatomy, the corresponding carpal bones are named differently (for example, scaphoid and lunate), and radiale is rarely used outside historical or cross-species contexts.