dinosaur bone thin section, from “marrow” (top) to outer surface (bottom). Magnification: photographed at 20x.

At still higher magnification, the cavities left by individual bone cells are visible, forming dark spots that are elongated parallel to the laminations around each canal (filled with blue epoxy). Also present are very fine (several microns) anastamosing channels extending from each cell cavity, known as caniculi. These are just barely visible as light-coloured filaments radiating from each dark cell cavity in the highest-magnification image. Most are oriented in a radial direction, perpendicular to the laminations of the bone around each haversian canal.