Its uropatagium had a distinct calcar. They have an unkeeled calcar and a short, round tragus. The metatibia has a calcar or curved spur. They have a keel on their calcar. Some insectivorous species of bats have an elaborate, pronounced calcar. In Venice, he met the illustrator Johan van Calcar, a student of Titian. The term "Merkel's spur" is synonymous with the femoral calcar. All megabats, however, lack any calcification in their calcar. The calcar varies widely among bats. "Onychonycteris" had a long calcar, indicative of a broad tail membrane. Its name comes from the Latin "calcar" meaning "spur". Megabats lacking the calcar or spur include "Notopteris", "Syconycteris", and "Harpyionycteris". They also possess a calcar and a slightly pigmented, permanently open dactylopatagium minus. The membrane at the rear is, however, supported by a calcar at the ankle. The oldest known bat with a calcar is "Onychonycteris", which lived in the early Eocene.