I came across this interesting article in the Summer 1982 issue of the Kronos journal (here is an excerpt):-
Source:-So large do the problems of angiosperm evolution and phylogenetic relationships loom in biology that we should turn for confirmation not just to deniers of Darwinian evolution but also to authorities committed to the possibility of discovering a Darwinian solution. Such a one is Norman Hughes. His recent book, Palaeobiology of Angiosperm Origins. Problems of Mesozoic Seed-Plant Evolution ( 1976), does not claim to offer the answers but only "to encourage faith in the adequacy of the fossil record for making possible a continuing and effective solution" (p. vii). Specifically, this is "faith" in recently developed techniques for the study of fossil pollen. This is indeed an important new area of study, and much new knowledge has recently been gained. However, the problem remains:
The evolutionary origin of the now dominant land-plant group, the angiosperms, has puzzled scientists since the middle of the nineteenth century. In late Cretaceous rocks angiosperm fossils were dominant, but in the early Cretaceous seed-plant fossils were almost entirely of gymnospermous types; the transition appeared to be sudden. (p.1)
And by "sudden," Hughes means more than can be handled by an equivocal term like punctuated equilibrium - recently popularized by Eldredge and Gould as "An Alternative to Phyletic Gradualism" (1972). Hughes means that nothing in or out of the fossil record can reasonably be the source of the botanical characteristics of angiosperms as a monophyletic group; there is no transition.
. . . It had for long been assumed that angiosperms were monophyletic and therefore that the immediate ancestor should have been traceable among the relatively few known fossil and Recent gymnosperm groups. None of these gymnosperm groups however appeared to carry a set of characteristics which was at all near to the requirement. (p.1)
Fossil pollen is not the first great hope of solving the problem of angiosperms; study of non-fossil pollen (palynology) was to have done the same. The incentive is more than academic interest; there is a conspicuous inability to agree on a taxonomy that plausibly reflects (even if it does not actually embody) phylogeny. The great need is to establish
the basis of classification of the living angiosperms, which still form the largest group of organisms without an agreed or satisfactory hierarchical arrangement of taxa. New information from such diverse sources as numerical taxonomy, chromosome numbers, palynology and chemotaxonomy appeared to complicate rather than to clarify the position in a most extensive literature. (p. 2)
Not for the first time do we find that an increase in knowledge confuses rather than clarifies phylogeny. In such cases, the quest for a phylogenetic basis of classification fosters disagreement even among those taxonomists with common evolutionary goals.
Nilsson's theory of emication is now over a quarter of a century old, but nothing has been discovered in the meantime to undercut angiosperms as a prime example of it. So too, the possibility of drawing diametrically opposed conclusions from them in the catastrophism/uniformitarianism debate remains the same:
It is remarkable that emication as well as catastrophe are simultaneous for all these groups. This cannot be explained by an evolution but manifestly illustrates a revolution. (Nilsson 1953: 1191)
Taking stratigraphy in its broadest sense as the evolutionary history of the earth, there is nothing exceptional about the Cretaceous period of that evolution. The invocation of a hiatus in orogeny, of worldwide transgressions or of great external catastrophe (Urey 1973) are entirely unnecessary to explain the known facts; . . . to account for apparent disharmonies such as the origin of angiosperms, the extinction of dinosaurs and other organisms, or the existence of chalk deposition. (Hughes 1976: 70)
Kronos Vol. VII No. 4 (Summer 1982) "Evolution, Extinction, and Catastrophism"
Alternatives in Science: The Secular Creationism of Heribert Nilsson by Bennison Gray