a. and sb. Anat. and Zool. Also (more correctly) xipho-. [f. xiphi- for xipho-, Gr. ξίφος sword + STERNUM + -AL.] a. adj. Belonging to or constituting the xiphisternum (see below). b. sb. A xiphisternal part or appendage. So ǁ Xiphisternum, the posterior division of the sternum, in some animals osseous and in others cartilaginous, in man constituting the xiphoid or ensiform cartilage; also sometimes applied to the XIPHIPLASTRON of a turtle.
1835–6. Todd’s Cycl. Anat., I. 284/1. The posterior cartilaginous appendages [of the sternum in birds] he [sc. Geoffrey St. Hilaire] terms xiphi-sternals. Ibid. (1839–47), III. 8381. The posterior [of the two pairs of elements of the ‘sternum,’ i.e., plastron, of Chelonia] are fitly denominated the xiphosternal pieces.
1870. Rolleston, Anim. Life, 15. The posterior or xiphisternal end of the sternum.
1872. H. A. Nicholson, Palæont., 399. The xiphisternum is the ‘xiphoid cartilage’ of human anatomy.
1888. Rolleston & Jackson, Anim. Life, 362. The sternum [in Mammalia] … is divisible into three regions—a praesternum or manubrium sterni…; a mesosternum…; and a xiphisternum, sometimes cartilaginous, sometimes ossified. Ibid., 384. [The] bilateral origin [of the sternum in some Lacertiliæ] is evidenced … by the prolongation backwards … of two xiphisternal horns.
