Obligation to point out the inventor and invention dates of each claim not commonly owned

In a recent first office action rejection, the examiner wrote the following:

“This application currently names joint inventors. In considering patentability of the claims under 35 U.S.C. 103(a), the examiner presumes that the subject matter of the various claims was commonly owned at the time any inventions covered therein were made absent any evidence to the contrary. Applicant is advised of the obligation under 37 C.F.R. 1.56 to point out the inventor and invention dates of each claim that was not commonly owned at the time a later invention was made in order for the examiner to consider the applicability of 35 U.S.C. 103(c) and potential 35 U.S.C. 102(e), (f) or (g) prior art under 35 U.S.C. 103(a).

I’m confused by this examiner statement. (Otherwise, this particular office action is exceptionally well written). What I don’t understand is the “obligation.” After receiving this (or even before) are the patent applicants under a duty to describe the ownership structure and invention dates?