Walk Like a Sloth–lesson 6: sternebrae and sternal ribs

Introduction to Walk Like a Sloth: lessons in ground sloth locomotion

compassGetting Oriented

SLOTH STERNUM,ventral view (Owen, 1842)

SLOTH STERNUM,ventral view (Owen, 1842)

Megalonyx has a sternum or breast bone composed of a stack of eight (8) separate bones called sternebrae  (singular is sternebra).  The sternebrae connect to the ribs through eight (8) pairs of bones called sternal ribs that curve around the front of the chest and connect to the true ribs with a thin layer of cartilage.  The triangle wide, flat, smooth back of the sternebrae is the “in” side or dorsal surface. Notice the protruding opposite side, called the ventral process, is heavily textured.  As in all Megalonyx bones, this increases the surface area for anchoring the sloth’s powerful muscles, in this case, the pectorals.

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