“Artists have often created objects with features that could only be viewed from a certain angle, and the sculptor who carved the Venus of Hohle Fels was evidently employing this technique when he personified the mushroom’s umbo.”

“The oldest part of the shell, the umbo, can be recognized as a large hump on the anterior end of the dorsal side of each shell.”

“Argonauta attaches the egg-mass to the umbo of the shell near the dorsal arms, not in the mantle cavity or posterior parts of the shell.”

“Species on this family can be identified by its mytiliform form, sometimes quadrate, with the hinge edentulous and the umbos anterior or terminal.”

“Below the umbones, the shell margin is folded inward forming a deep lunula and gaping between both valves.”

“The shell is ventricose, is closed or gapes slightly posteriorly, and has prominent subcentral umbones and an external ligament.”

“The two valves are roughly triangular or bluntly oblong with rounded umbones near the anterior end.”