Archaeopteryx lithographica (Berlin specimen)

This is a partial list of

transitional fossils A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. This is especially important where the descendant group is sharply differentiated by gross a ...

(fossil remains of groups that exhibit both "primitive" and derived traits). The fossils are listed in series, showing the transition from one group to another, representing significant steps in the evolution of major features in various lineages. These changes often represent major changes in morphology and anatomy, related to mode of life, like the acquisition of feathered wings for an aerial lifestyle in

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

, or limbs in the

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...

transition onto land. Darwin noted that transitional forms could be considered

common ancestor Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal comm ...

s, direct ancestors or collateral ancestors of living or extinct groups, but believed that finding actual common or direct ancestors linking different groups was unlikely. Collateral ancestors are relatives like cousins in genealogies in which they are not in your direct line of descent but do share a common ancestor (in this case it is a grandparent). This kind of thinking can be extended to groups of life. For instance, the well-known '' Archaeopteryx'' is a transitional form between non-avian dinosaurs and birds, but it is not the most recent common ancestor of all birds nor is it a direct ancestor of any species of bird alive today. Rather, it is considered an extinct close evolutionary "cousin" to the direct ancestors. This may not always be the case, though, as some fossil species are proposed to be directly ancestral to others, like how ''

Australopithecus anamensis ''Australopithecus anamensis'' is a hominin species that lived approximately between 4.2 and 3.8 million years ago and is the oldest known ''Australopithecus'' species, living during the Plio-Pleistocene era. Nearly one hundred fossil specimens ...

'' is most likely to be ancestral to ''

Australopithecus afarensis ''Australopithecus afarensis'' is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would not ...

''.

Nautiloids to ammonoids

Cephalopods

Evolution of insects

Evolution of spiders

Invertebrates to fish

Chondrichthyes Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. ...

Bony fish

Fish to tetrapods

Amphibians to amniotes

Turtles

From lizards to snakes

Lizards

Pterosaurs

Archosaurs to dinosaurs

Dinosauria

Dinosaurs to birds

Bird evolution

Non-mammalian synapsids to mammals

Evolution of mammals

Early artiodactyls to whales

Evolution of sirenians

Evolution of pinnipeds

Evolution of the horse

Human evolution

List of human evolution fossils The following tables give an overview of notable finds of hominin fossils and remains relating to human evolution, beginning with the formation of the tribe Hominini (the divergence of the human and chimpanzee lineages) in the late Miocene, roug ...

References

External links

Vuletic.com
Section V: Paleontology – Transitional fossils between every animal group

Palaeos vertebrates starting with lobe-finned fish (very comprehensive)

FAQ: Transitional vertebrate fossils
(A few) transitional fossils
{{DEFAULTSORT:Transitional Fossils * Lists of prehistoric animals