Webster’s Revised Unabridged Dictionary · 1913
Coetaneous
Co′e·ta′ne·ous (·ŭs), a. [L. coaetaneus; co- + aetas age.] Of the same age; beginning to exist at the same time; contemporaneous.
— Co′e·ta′ne·ous·ly, adv.
And all [members of the body] are coetaneous. Bentley.