I remember shared libraries on SunOS 4.x. SunOS 4.x was retroactively renamed to Solaris 1 sometime around the first Solaris 2 (SunOS 5.x) release. I ran it on both a Sun 3/60 and a Sparc. Up until Solaris 2.4 or so, most folks still preferred the older SunOS.
EDIT: http://iraf.noao.edu/docs/src/dosf/unixsmg-N-3.2.html indicates that BSD based SunOS did offer shared libraries (at least late in its live, as early on it was a 3rd party project to add those: https://pdfs.semanticscholar.org/0433/bb8fb59cc457b74b3f8ad0...).