There is a drawing of "Enigmophyton superbum" in Andrews' Studies in Paleobotany (by Henry N Andrews, John Wiley & Sons 1961, 487 pp., Fig.2-11., p. 55) called "a problematical fossil from the Devonian of Spitsbergen." The drawing (from Hoeg, 1942) shows fan-shaped leaves that look very much like Ginkgo. The text notes that it "is thought to have attained a height of 1 meter or more; the smooth stems were 5 mm in diameter and bore lateral branches about 1 to 2 mm thick. The leaf developed from a narrow base into a partially dissected fan-shaped structure some 16 cm long and 12 cm broad. Although woody tissue has not been observed in the stems the impressions of regularly spaced lines, which apparently indicate veins in the leaves, allow little doubt that it was a vascular plant." It goes on to describe lycopod-like fructifications that are found with it. The lines on the leaves in the drawing bifurcate, but do not form netted veination. I don't think anyone would claim that it is an angiosperm; but it is very interesting to find such plant remains in strata considered to be Devonian. It would not be such an "enigma" if it were found in Mesozoic strata. There it might be considered among the "problematic gymnosperms". I haven't found it mentioned in more recent paleobotany texts.
Of course there were net-veined leaves on non-angiospermous plants, most notably the pteridosperm Glossopteris, abundant in Permian (and some Triassic) sediments of Australia, South Africa, South America, Antarctica, and India (the Gondwana Flora). H.P.Banks in "Evolution and Plants of the Past" (Wadsworth, 1970, 170 pp.) doesn't mention glossopterids, but does claim, (p.148) "Long before the first angiosperms appeared most of the anatomical and morphological features which they possess had already evolved!" although he does not describe these, and "Only when all the various characteristics were finally assembled into one organism did we have the first angiosperm." although he doesn't tell us how such trans-divisional migration of characterists could occur. I have seen other papers on angiosperm origins claiming some kind of "jumping genes". Each of the evolutionary theories of angiosperm origins brings up more questions than answers. It is interesting that N.F.Hughes book titled "Palaeobiology of Angiosperm Origins" (Cambridge University Press 1976) was retitled "The enigma of angiosperm origins" in 1994. N.F.Hughes was one who insisted that there were no pre-Cretaceous angiosperms.
I think paleobiology shows more and more clearly that the angiosperms appear in Cretaceous sediments without showing us their ancestry!
2010 Arthur V. Chadwick, Ph.D.