Which group of Mesozoic-aged gymnosperm seed plant is the angiosperm descended from?

i thing angio sperms decended from a relatively smaller plants compared to precent day conifers

The family Amborellaceae is regarded as the sister family of all living flowering plants. That means members of this family were most likely the first flowering plants. However, we still do not know what gymnosperm was the ancestor of flowering plants.

It seems that on the level of the organ, the leaf may be the ancestor of the flower, or atleast some floral organs. When we mutate some crucial genes involved in flower development, we end up with a cluster of leaf-like structures. Thus, sometime in history, the developmental program leading to formation of a leaf must have been altered to generate a flower. There probably also exists an overall robust framework within which the floral diversity has been generated. A example of that is a gene called LEAFY (LFY), which is involved in flower development in Arabidopsis. The homologs of this gene are found in angiosperms as diverse as tomato, snapdragon, pea, maize and even gymnosperms. Interestingly, expression of Arabidopsis LFY in distant plants like poplar and citrus also results in flower-production in these plants. The LFY gene regulates the expression of some gene belonging to the MADS-box family. These genes, in turn, act as direct controllers of flower development.