pertaining to the entosternum or median piece of the sternum or breastbone, very largely developed in birds. [After French entosternal (1818 or earlier).]
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1835–6 Todd's Cycl. Anat. & Physiol. I. 284/1 A middle one [i.e. centre] which supports the keel, termed..the entosternal.
1854 R. Owen in Circle of Sci. (c1865) II. 69/2 The median piece of the plastron, called ‘entosternal’, answers to the sternum of the crocodile.