The Collaborative International Dictionary of English v.0.48:

Cotemporaneous \Co*tem`po*ra"ne*ous\ (k?-t?m`p?-r?"n?-?s), a.
   [See Contemporaneous.]
   Living or being at the same time; contemporaneous. --
   Co*tem`po*ra"ne*ous*ly, adv. -- Co*tem`po*ra"ne*ous*ness,
   n.
   [1913 Webster]