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A transitional fossil is a fossil which bridges two major taxonomic groups. According to the theory of evolution, new species arise as a consequence of new traits that appear in a lineage; if this theory is correct, any life-forms which exist in the middle of this process would be a sort of mosaic, combining old traits from the ancestral form with new traits that are not found in the ancestral form. In the context of biological science, therefore, the word "transitional" (as seen in the phrases "transitional fossil" or "transitional form") refers to precisely this sort of mosaic life-form.
Creationists and Transitional Fossils
Creationists typically deny that any transitional forms have ever existed; the intellectual gyrations they go through so that they can continue refusing to acknowledge the transitional nature of such specimens as Archaeopteryx are a testimonial to the power of preconceived notions.
Some Examples of Transitional Fossils
The following is a list of more notable transitional fossils, both for their fame in some cases and more often, the astonishing degree to which their anatomy conforms with predictions as to what a transitional form between any given taxa should look like. All of these species and genera display a mosaic of primitive and advanced characters bridging taxonomic gulfs and are thus ideal "missing links," to use the most popular rendering of transitional fossil.
- Acanthostega gunnari
- Ichthyostega stenisoei
- Pederpes finneyae
- tiktaalik roseae
- panerichthys rhombolepis
- Prolacerta spp.
- Protorosaurus spp.
- Euparkeria capensis
- Chasmatosaurus spp.
- Sphenosuchus acutus
- Terrestrisuchus spp.
- Sclermochlus taylori
- Eoraptor lunensis
- Herrerasaurus ischigualastensis
- Staurikosaurus pricei
- Sinornithosaurus millenni (See Downy Dinos)
- Microraptor spp. (See Downy Dinos)
- Sinovenator changii
- Archaeopteryx lithographica (See Archaeopteryx)
- Confuciusornis sanctus (See Urvogel Take Two: Confuciusornithidae and the Early Evolution of Birds)
- Iberomesornis romerali (See Enantiornithes)
- Sinornis santensis (See Enantiornithes)
- Chaoyangia beishanensis (See Urvogel Take Two: Confuciusornithidae and the Early Evolution of Birds)
- Liaoningornis longidigitus (See Urvogel Take Two: Confuciusornithidae and the Early Evolution of Birds)
- Yanornis martini
- Yixianornis grabaui
- Jeholornis prima
- Graculavus spp. (See The Neornithine 'Big Bang')
- Cimolopteryx spp. (See The Neornithine 'Big Bang')
- Palintropus spp. (See The Neornithine 'Big Bang')
- Tyttostonyx glauconiticus (See The Neornithine 'Big Bang')
- Presbyornis pervetus (See The Neornithine 'Big Bang')
- Juncitarsus spp. (See The Neornithine 'Big Bang')
- Rhynchaeites messelensis (See The Neornithine 'Big Bang')
- Limnofregata azygosternon (See The Neornithine 'Big Bang')
- Lithornis spp. (See The Neornithine 'Big Bang')
- Salmila robusta (See A new gruiform from Messel, The Neornithine 'Big Bang')
- Psilopterus spp.
- Procariama spp.
- Gallinuloides wyomingensis
- Foro panarium
- Eomaia scansoria
- Ambulocetus natans
- Sahelanthropus tchadensis