It was during the Devonian Period when gymnosperms evolved from the seed ferns
However, gymnosperm are plant species whose seeds are not confined in an ovary. For example - conifer
In the period of Mesozoic era , the scorpionflies ( species feeding on pollination drops) carried out pollination of gymnosperm and led to the coevolution of insects feeding on nectar which later on drove the evolution of angiosperms and also themselves.
Thus, it can be said the flowers and its pollinators evolved simultaneously.
I presume you are referring to t<span>he fossil plant Elkinsia polymorpha, which is considered the earliest known seed plant, producing seeds along its leaves. </span>
