Every fossil, and indeed every living creature, is transitional between an older form and a newer (or yet to come) form. We have a pretty good collection of fossils that show a transition from older forms to newer forms, such as the transition of large land mammals to whales. Scientists using the Theory of Evolution have even predicted a transitional form and where to find it. This transitional fossil, tiktaalik, was found based on these predictions.
More details have emerged about the anatomy of Tiktaalik, the "fishopod" that bridges the gap in evolutionary history between swimming fish and four-legged land-dwelling animals. The new findings bolster its position as a key transition or "missing link" fossil.
Keep in mind, POPULATIONS evolve, NOT individuals. That is a huge misunderstanding that creationists seem unwilling to learn. There is no such thing as Cameron's crockoduck. It never could exist, and the theory of evolution never said it would. Nor is there a fronkey, or any other such nonsense. I suggest you read these books (Why Evolution is True and The Greatest Show on Earth) to get an idea of what evolution actually states as opposed to the gross caricature you seem to have in your head.
National Geographic published this article back in Feb, 2009. It does a nice job listing some of the better documented transitions we have (although not the only 7, just some of the ones that would be impossible to ignore without willful mental gymnastics). They give you Tiktaalik (like I did), Archaeopteryx, Amphistium, Ambulocetus, Homo Ergaster, Hyracotherium/Eohippus, and Thrinaxodon. And here is an even longer list of transitional fossils. Or if you prefer, the wikipedia list.
Michael Shermer tackles this assertion straight on.
- There are no transitional forms in the fossil record, anywhere, including and especially humans. The whole fossil record is an embarrassment to evolutionists. What about Neanderthals? These are all diseased skeletons-arthritis, rickets, etc., that create the bowed legs, brow ridge, and larger skeletal structure. Homo erectus, and Australopithecus, are just apes.
Creationists like to quote Darwin's famous passage in the Origin of Species in which he asks: "Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the gravest objection which can be urged against my theory." One answer is that there are plenty of examples of transitional forms that have been discovered since Darwin's time. Just look in any paleontology text. A second answer was provided in 1972 by Eldredge and Gould when they demonstrated that gaps in the fossil record do not indicate missing data of slow and stately change; rather, it is evidence of rapid and episodic change. Using Mayr's "allopatric speciation," where small and unstable "founder" populations are isolated at the periphery of the larger populations's range, they show that the relatively rapid change in this smaller gene pool creates new species but leaves behind few, if any, fossils. The process of fossilization is rare and infrequent anyway. It is almost nonexistent during these times of rapid speciation. A lack of fossils is evidence for rapid change, not missing evidence for gradual evolution.
Scientific American adds this in an article debunking 15 unoriginal and poorly thought out false assertions by creationists:
- Evolutionists cannot point to any transitional fossils--creatures that are half reptile and half bird, for instance.
Actually, paleontologists know of many detailed examples of fossils intermediate in form between various taxonomic groups. One of the most famous fossils of all time is Archaeopteryx, which combines feathers and skeletal structures peculiar to birds with features of dinosaurs. A flock's worth of other feathered fossil species, some more avian and some less, has also been found. A sequence of fossils spans the evolution of modern horses from the tiny Eohippus. Whales had four-legged ancestors that walked on land, and creatures known as Ambulocetus and Rodhocetus helped to make that transition [see "The Mammals That Conquered the Seas," by Kate Wong; Scientific American, May]. Fossil seashells trace the evolution of various mollusks through millions of years. Perhaps 20 or more hominids (not all of them our ancestors) fill the gap between Lucy the australopithecine and modern humans.
Creationists, though, dismiss these fossil studies. They argue that Archaeopteryx is not a missing link between reptiles and birds--it is just an extinct bird with reptilian features. They want evolutionists to produce a weird, chimeric monster that cannot be classified as belonging to any known group. Even if a creationist does accept a fossil as transitional between two species, he or she may then insist on seeing other fossils intermediate between it and the first two. These frustrating requests can proceed ad infinitum and place an unreasonable burden on the always incomplete fossil record.
Nevertheless, evolutionists can cite further supportive evidence from molecular biology. All organisms share most of the same genes, but as evolution predicts, the structures of these genes and their products diverge among species, in keeping with their evolutionary relationships. Geneticists speak of the "molecular clock" that records the passage of time. These molecular data also show how various organisms are transitional within evolution.
And because I also have this at my fingertips, here is Calilasseia's reply to this oft debunked canard.
(14) The "no transitional forms" canard.
In order to deal with this one, I have the following to ask. Namely:
(1) Have you ever studied comparative anatomy in detail, at a proper, accredited academic institution?
(2) Do you understand rigorously what is meant by "species"?
(3) Do you understand even the basics of inheritance and population genetics?
(4) Do you understand the basics of the workings of meiosis?
If you cannot answer "yes" to all four of the above, then you are in no position to erect this canard. And, canard it is, as anyone with a proper understanding of the dynamic nature of species will readily understand, a topic I have posted at length on in the past. Indeed, you only have to ask yourself the following question, "Am I identical to either of my parents?" in order to alight quickly upon why this canard IS a canard. Your own family photo album supplies you with the answer here. YOU are a "transitional form" between your parents and your offspring, should you have any offspring.
If you want a good visualization of evolution, maybe this picture will help you with some shorthand:
THAT is a logical process that seems to escape people who deny evolution. Again, I suggest you read up more at one of the earlier links provided.
EDIT TO ADD: And the ever popular goalpost moving, ThirdIdiot (or whatever name he's using) has asked for transitional fossils in the line of human evolution. If that link is not enough, there is the Stephen Jay Gould list of links that may also provide a great deal of information. Of course, that assumes you are willing to let go of the wildly inaccurate caricature of evolution that you seem to be holding on to.