The uncinate processes of the ribs are extensions of bone that project caudally from the vertical segment of each rib. (Uncinate means hooked from Latin uncinatus, from uncinus, barb, from uncus, hook.) They are found in birds, reptiles and the early amphibian Ichthyostega.
These processes can serve to attach scapula muscles, and help to strengthen the rib cage overlapping with the rib behind them. They are also shown to have a role in respiration by increasing the effectiveness of muscles involved in inspiration including the appendicocostal muscles. The processes are short in walking birds and long in diving species and are of intermediate length in non-specialist birds. The screamers (Anhimidae) are unique in lacking this process. The process has also been noted in some Enantiornithines. Although bony uncinate processes are unique to birds, cartilaginous uncinate processes are present in crocodiles. The uncinate process has also been reported in Sphenodon, Caudipteryx, oviraptorids, Confuciusornis and Chaoyangia however it does not occur in Archaeopteryx.
Famous quotes containing the words processes and/or ribs:
“The higher processes are all processes of simplification. The novelist must learn to write, and then he must unlearn it; just as the modern painter learns to draw, and then learns when utterly to disregard his accomplishment, when to subordinate it to a higher and truer effect.”
—Willa Cather (1873–1947)
“Grammar is a tricky, inconsistent thing. Being the backbone of speech and writing, it should, we think, be eminently logical, make perfect sense, like the human skeleton. But, of course, the skeleton is arbitrary, too. Why twelve pairs of ribs rather than eleven or thirteen? Why thirty-two teeth? It has something to do with evolution and functionalism—but only sometimes, not always. So there are aspects of grammar that make good, logical sense, and others that do not.”
—John Simon (b. 1925)