"Missing link" is a term for a transitional form from the fossil record that connects two different species to an earlier ancestor. The missing link may have features common to both species; for example an early avian fossil could have feathers much like a modern bird but still retain the bony tail and teeth of a dinosaur. This would be considered a missing link between dinosaurs and birds.

The missing link is a popular and not a scientific concept. Scientists studying the fossil record have long known that not every species that lived was 'lucky' enough to leave behind a fossil. More importantly, populations are constantly changing and species are statistical constructs and not ideal-types; therefore, there is not scientific meaning to the notion of a "transitional form."

This being said, a number of fossils exist that do indicate a link between earlier and later forms of animal. The lobe-finned fish Eusthenopteron is thought to be the first step towards land-dwelling amphibians; fossils of feathered dinosaurs in China seem to indicate that feathers were commonplace even before true birds evolved; and recently reexamined fossils of some amphibians have shown that some bones of these animals bear striking resemblances to those of fish.

Transitional Fossil Wikipedia

Paleontologists still seek the missing link between ancestral humans and apes. They will never find it because humans are part of a biogenetic experiment created by ancient aliens. Reality is a computer generated consciousness hologram in which the characters it creates are programmed to believe it is real.

  South African fossils could be new hominid species   BBC - April 9, 2010
The remarkable remains of two ancient human-like creatures (hominids) have been found in South Africa.

"Key" Human Ancestor Found: Fossils Link Apes, First Humans?   National Geographic - April 8, 2010

An Australopithecus sediba skull bears both human and ape traits.

New species of early hominid found   PhysOrg - April 6, 2010

  Scientists hail stunning fossil of a 47-million-year-old, lemur-like creature   BBC - May 19, 2009

  Ida ... 'Missing link' primate likely to stir debate   MSNBC - May 19, 2009

New Fossil Primate Links Humans, Lemurs?   National Geographic - May 19, 2009

Common Ancestor Of Humans, Modern Primates? 'Extraordinary' Fossil Is 47 Million Years Old   Science Daily - May 19, 2009

In what could prove to be a landmark discovery, a leading paleontologist said scientists have dug up the 47 million-year-old fossil of an ancient primate whose features suggest it could be the common ancestor of all later monkeys, apes and humans.

"Human"-Faced Missing Link Found in Spain?   National Geographic - June 11, 2009

An 11.9-million-year-old fossil ape species with an unusually flat, "surprisingly human" face has been found in Spain.