This might be it, but i think the T-Rex had more skin than that:
Zero X: TV21 & TV Tornado - 1969
and Countdown - 1971
Journey To The Planet Of Bones (Story Eighteen)
Writer: 'James Freeman' (Angus P. Allan).
Artist: Mike Noble. 2 pages, colour.
A huge skeleton hand erupts from the surface, and tries to grab Greg.
Paul blasts it with his laser, and it drops the copilot to vanish back
into the depths. Pierce surmises disease or disaster overtook the
primitive animals, leading to a new form of evolution - independent
living bones. It was a stray skull which killed Vatski and destroyed
the Zenith 4, but Paul feels they should destroy the pool to prevent
further incidents. But as he speaks, the pool erupts, and a full skull
and skeleton emerges. Pierce admits he is wrong, and that bones are
not the end of the evolution but the beginning. A complete living
skeleton is the birth of a new species, and a whole race may be
spawned by the pool at any minute...