"The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology. The evolutionary trees that adorn our textbooks have data only at the tips and nods of their branches; the rest is inference, however reasonable, not the evidence of fossils. Yet Darwin was so wedded to gradualism that he wagered his entire theory on a denial of this literal record." (Gould, Stephen J. "The Panda’s Thumb, 1980, p. 181)
"Fossil discoveries can muddle over attempts to construct simple evolutionary trees--fossils from key periods are often not intermediates, but rather hode podges of defining features of many different groups... Generally, it seems that major groups are not assembled in a simple linear or progressive manner--new features are often "cut and pasted" on different groups at different times." (Shubin, Neil, "Evolutionary Cut and Paste," Nature, vol. 349, 1998, p. 39.)
"Well, we are now about 120 years after Darwin and the knowledge of the fossil record has been greatly expanded. We now have a quarter of a million fossil species but the situation hasn’t changed much. The record of evolution is still surprisingly jerky and, ironically, we have even fewer examples of evolutionary transition than we had in Darwin’s time. By this I mean that some of the classic cases of Darwinian change in the fossil record, such as the evolution of the horse in North America, have had to be discarded or modified as a result of more detailed information..." (Raup, David M., "Conflicts Between Darwin and Paleontology," Field Museum of Natural History Bulletin, vol. 50, 1979, p. 25.)
"Large evolutionary innovations are not well understood. None has ever been observed, and we have no idea whether any may be in progress. There is no good fossil record of any." (Wesson, R., Beyond Natural Selection, 1991, p. 206)