What is "umbo"

Umbo \Um"bo\, n.; pl. L. Umbones, E. Umbos. [L.]

1. The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.

2. A boss, or rounded elevation, or a corresponding depression, in a palate, disk, or membrane; as, the umbo in the integument of the larv[ae] of echinoderms or in the tympanic membrane of the ear.

3. (Zo["o]l.) One of the lateral prominence just above the hinge of a bivalve shell.

"boss of a shield," 1921, from Latin umbo "shield-boss, knob, projection."

n. 1 (context biology English) A boss, or rounded elevation, or a corresponding depression, in a palate, disk, or membrane; as, the umbo in the integument of the larvæ of echinoderms or in the tympanic membrane of the ear. 2 (context zoology English) One of the lateral prominence just above the hinge of a bivalve shell. 3 (context mycology English) A bump or protrusion on the top of the cap. 4 (context historical English) The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.

1. n. a slight rounded elevation where the malleus attaches to the eardrum

2. [also: umbones (pl)]

Umbo may refer to:

• Umbo of tympanic membrane – The central, most inverted portion of the ear drum
• A shield boss
• umbo (mycology), at the top of some mushrooms
• Umbo (bivalve) is the (often somewhat protruding) part of a Bivalve shell which was formed when the animal was a juvenile
• The first year's growth of a seed scale on a pine cone, showing up as a protuberance at the end of the two-year-old scale
• The tiny depression in the very center of the foveola, and corresponds to the foveal reflex.
• Otto Umbehr, German photographer

thumb|right|Cantharellula umbonata has an umbo. thumb|right|The cap of Psilocybe makarorae is acutely papillate. An umbo is a raised area in the center of a mushroom cap. Caps that possess this feature are called umbonate. Umbos that are sharply pointed are called acute, while those that are more rounded are broadly umbonate. If the umbo is elongated, it is cuspidate, and if the umbo is sharply delineated but not elongated (somewhat resembling the shape of a female breast), it is called mammilate or papillate.

The umbo (plural umbones or umbos) is the vaguely defined, often most prominent, highest part of each valve of the shell of a bivalve or univalve mollusk. It usually contains the valve's beak, the oldest point of the valve, and its degree of prominence and its position relative to the hinge line are sometimes helpful in distinguishing bivalve taxa. The umbo forms while the animal is a juvenile, and radial growth subsequently proceeds around that area. The umbo (plural umbones or umbos) is situated above the hinge line. In those bivalves where the umbones do not protrude, as is the case for example in some mussels, the umbones can nonetheless usually be readily identified by examining the concentric growth lines of the shell.

Umbo is also in use in anatomic descriptions of brachiopods, for the origin of growth of the valves.