Speculation on Pre-Cretaceous Angiosperms has been made by several authors, and many authors have hypothesized the possible mechanisms of the evolutionary change. Many of the purported pre-angiosperm ancestors have "angiosperm" leaf characters (net-like venation pattern) which has arisen independently in several clades.

The apparent burst of monocot and dicot angiosperms into the fossil record without "transitional" forms has led workers to a quandary and a search for pre-Cretaceous angiosperms. There is little doubt that angiosperms display the most advanced seed plant state, and that the features that characterize them originated from a gymnosperm ancestor.

The Gnetales, a small relict group of gymnosperms, may hold the key to angiospermy. Recent investigations have shown that one of the primary characters of angiospermy - double fertilization, anastomosing leaf venation, reduction of the male gametophyte, tetrasporic megagametophyte with free nuclei serving as eggs, and a feeder in the embryo - occurs sporadically in Ephedra, and a welwitschian-type reproductive structure (Archaestrobilus) found in the Late Triassic of Texas has been interpreted to have been a precursor to angiosperms. There is growing agreement that these plants may be the closest living relative to flowering plants.

A recent discovery in China of the world's oldest flower, Archaefructus liaoningensis, has pushed the earliest evidence of this group to the Berriasian (earliest Cretaceous) at 142 MY BP. The fossils were recovered from a lake deposit in which limestones and volcanic ashes accumulated.

The most abundant angiosperm remains are known from the Potomac Group in Virginia. Doyle and Hickey (1976) have demonstrated that both pollen (monocolpate) and leaves (laminate, entire) of angiospermous origin exist there, and recently Friis et al. (1994) have recovered remains of flowers. These assemblages are poorly diversified and morphologically possess "disorganized" patterns. Their arrival into depositional sites has spawned postulation that the group originated in a variety of settings:

Recent discoveries of a herbaceous angiosperm fossil record in the Early Cretaceous has led to two competing hypotheses - that early angiosperms were paleoherbs, rather than trees or shrubs.

Albian 113-97.5 MY Flowers with four gynoecial valves and an erect ovule Reticulate tricolpate pollen
Aptian 119-113 MY Expanded laminae with reticulate venation pattern; Tricolpates & Monoporates
Barremian 124-119 MY Zone I (Doyle & Hickey, 1977) leaves are predominantly entire, some marginally toothed leaves, and only 1 with lobate leaves. Afropollis, Brenneripollis and tricolpate pollen
Hauterivian 131-124 MY Flowers (Friis, Pedersen & Crane 1994) weakly Monosulcate
Valanginian 137-131 MY Tectate-columellae structure (Brenner & Bickoff, 1992)
Berriasian 144-137 MY Flowers (Dilcher et al., 1998)