Transitional fossil
From Palaeos
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[edit] Introduction
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.
[edit] 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.
[edit] Some Examples of Transitional Fossils
The following is a list of more notable transitional tetrapod 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.
Other examples could be found among invertebrates, for example the possible basal Lophotrochozoan (or Eutrochozoan) Halkeria, and among plants, e.g. the Trimerophyta
[edit] Early Tetrapods
- Acanthostega gunnari
- Ichthyostega stenisoei
- Pederpes finneyae
[edit] Archosauria
- Prolacerta spp.
- Protorosaurus spp.
- Euparkeria capensis
- Chasmatosaurus spp.
- Sphenosuchus acutus
- Terrestrisuchus spp.
- Sclermochlus taylori
- Eoraptor lunensis
- Herrerasaurus ischigualastensis
- Staurikosaurus pricei
- Sinornithosaurus millenni
- Microraptor spp.
- Sinovenator changii
[edit] Aves
- Archaeopteryx lithographica
- Confuciusornis sanctus
- Iberomesornis romerali
- Sinornis santensis
- Chaoyangia beishanensis
- Liaoningornis longidigitus
- Yanornis martini
- Yixianornis grabaui
- Jeholornis prima
- Graculavus spp.
- Cimolopteryx spp.
- Palintropus spp.
- Tyttostonyx glauconiticus
- Presbyornis pervetus
- Juncitarsus spp.
- Rhynchaeites messelensis
- Limnofregata azygosternon
- Lithornis spp.
- Salmila robusta
- Psilopterus spp.
- Procariama spp.
- Gallinuloides wyomingensis
- Foro panarium
[edit] Mammals
- Eomaia scansoria
- Haplodactes
- Pakicetus
- Ambulocetus natans
- Basilosaurus
- Rhodocetus
[edit] Links
[edit] Credits
This page incorporates material from EvoWiki and so is licensed under the Attribution-NonCommercial-ShareAlike Creative Commons License). EvoWiki url: http://wiki.cotch.net/index.php/Transitional_fossils
