List of Transitional Fossils - Fish To Tetrapods

Fish To Tetrapods

The Fish → Tetrapods Evolutionary Series
Appearance Taxa Relationships Status Description Image
416-359 Ma

Genus:

  • Osteolepis
 An early member of the Tetrapodomorpha, the piscine line leading to tetrapods, Osteolepis is generalised enough to give a fair approximation of the common ancestor of tetrapods and lungfish. Fish A small to medium sized sarcopterygian fish with internal nostrils and pectoral fins stiffened by bony components broadly homologous to the humerus and radius/ulna found in tetrapods.
385 Ma

Genus:

  • Eusthenopteron
Belonging to the family Tristichopteridae, a family that form a sister group to Panderichthys and the tetrapods. Though not on the evolutionary path to tetrapods, Eusthenopteron is of fairly general build and is very well known, serving as an iconic model organism in tetrapod evolution. A medium sized, mainly pelagic fish, Eusthenopteron mainly use the pectoral and pelvic fins for navigation, and the tail for propulsion. The fin was of diphycercal, foreshadowing the straightening of the spine and the evolution of a contiguous fin in fish like Panderichthys
380 Ma

Genus:

  • Panderichthys
 Very close to the origin of tetrapods, a "fishapod" elpistostegalian. Fish A large, predatory shallow water fish. As common in shallow water fish, the pectoral and pelvic fins were flexible and paddle-like for propulsion. The dorsal and anal fins are lost, the tail fin contiguous. The spiracles were short and wide, indication large amount of oxygen were taken up by the lungs rather than through the gills.
375 Ma

Genus:

  • Tiktaalik
 A "fishapod" more tetrapod-like than Panderichthys. A fish, transitional between fish and the early, fish-like labyrinthodonts. "Fish" with stout, fleshy pectoral fins with a joint between the innermost and the two next bony elements, corresponding to the elbow in higher tetrapods. The cleithrum bone was free of the skull, functioning as anchoring for the pectoral fins, and at the same time allowing for movement of the neck.
368 Ma

Genus:

  • Elginerpeton
 Analysis of the cranial material shows it was more advanced than Tiktaalik, and together with Obruchevichthys form a sister group to the higher tetrapods. A fairly fragmentary find, Elginerpeton straddles the fish/tetrapod divide with a mosaic of features resembling 'Panderichthys, Ichthyostega and Hynerpeton. Probably one of the "fishapods". Though fragmentary, the find includes a shoulder blade (Cleitrum bone) as well as elements of the limbs, which shows it had comparable limbs Ichthyostega and Hynerpeton, indicating feet rather than fins.
365 Ma

Genus:

  • Ventastega
 Known only from fragmentary remains, mostly a lower jaw, Ventastega is morphologically midway between Tiktaalik and Acanthostega/Ichthyostega. Possibly oldest animal to have feet rather than fins. A large, dorso-ventrally flattened predatory fish with a well armoured labyrinthodont-like skull. While the fins themselves has not been found, the shoulder girdle is essentially similar to that of Acanthostega, indicating it too had feet rather than fins.
365 Ma

Genus:

  • Acanthostega
 Together with Ichthyostega the sole early labyrinthodont known from fairly complete skeletons. It is the oldest animal known to have feet rather than fins, thus making it a true tetrapod and the oldest known unquestionable ichthyostegalian. First known animal with toes rather than fins. The feet were broad and paddle-like, adapted for movement in water. It retained functional gills in adulthood, behind a fleshy operculum.
365 Ma

Genus:

  • Ichthyostega
 Fairly closely related to Acanthostega. It possibly represent an early (and ultimately unsuccessful) line adapted to moving on land by inchworm-like movements. Together with Acanthostega the sole early labyrinthodont known from fairly complete skeletons. Early labyrinthodont with polydactylous, paddle-like feet and reinforced vertebrae and neural spines. It probably spent time on land, yet retained gills and a tail with fin rayes.
360 Ma

Genus:

  • Hynerpeton
 While known only from fragmentary remains, it is more advanced than Ichthyostega. Early labyrinthodont amphibian A large, basically salamander-like creature. The shoulder girdle was powerful, indicating it was a competent walker.
??? Ma

Genus:

  • Tulerpeton
 An advanced ichthyostegalian, it straddle the divide between the fish-like Devonian forms and the more advanced Carboniferous amphibians. It has been suggested it is an early reptil-like amphibian. A large animal with paddle-like six-toed feet. It did however not have gills in adulthood, and is thus the oldest labyrinthodont known to depend entirely on breathing with its lungs.
359 - 345 Ma

Genus:

  • Pederpes
 Hailing from the fossil-poor Romer's Gap, Pederpes may be ancestral to the higher labyrinthodonts. Intermediate between the earlier Ichthyostegalian and the later, more advanced labyrinthodonts. Despite an extra toe on the forelimbs, Pederpes had limbs that terminated in feet adapted primarely for walking rather than paddles for combined swimming and walking like the earlier groups.
295 Ma

Genus:

  • Eryops
 The Temnospondyli are derived paleozoic amphibians, possibly ancestral to modern amphibians A "classical" temnospondyl, an advanced labyrinthodont group. One of the best known labyrinthodonts, Eryops combines the large, flat skull and short limbs typical of the group.
The Labyrinthodontia → Lissamphibia Evolutionary Series
Appearance Taxa Relationships Status Description Image
290 Ma

Genus:

  • Gerobatrachus
 Colloquially referred to as a "frogamander" due to this taxon being both chronologically and morphologically basal to both anurans and salamanders One of the first transitional fossils towards modern amphibians (Lissamphibia). Primitive traits
  • Backbone with intermediate characteristics
  • Retains a fully developed tail

Derived traits

  • Bears a large space for a tympanic ear
  • Ankle bones are fused together like in salamanders
  • Lightly built wide skull as in frogs

250 Ma

Genus:

  • Triadobatrachus
 Intermediate between generalized amphibians and derived frogs Early "almost frog" transitional amphibian Primitive traits
  • Possessed short limbs and therefore was unable to hop, unlike all extant anurans
  • Retains fourteen vertebra unlike modern frogs who have four to nine vertebra
  • Tibia and fibula are not fused into a tibiofibula

Derived traits

  • Skull resembles that of modern anuran skull with a latticework of thin bones in skull

190 Ma

Genus:

  • Prosalirus
 Another transitional form which could be properly classified as a frog An intermediate form which may replace Triadobatrachus as the "ultimate" ancestor of anurans Primitive traits
  • Still possess relatively short limbs

Derived traits

  • Tail is greatly reduced
  • Does not have greatly enlarged legs, but shows some adaptations for hopping, such as a three-pronged pelvis
213-188 Ma

Genus:

  • Vieraella
 A derived fossil frog completing the series of transitional fossils between early amphibians and modern anurans The oldest "true" frog Primitive traits
  • Retains ten presacral vertebra

Derived traits

  • Hind legs are adapted for hopping

210 Ma

Genus:

  • Eocaecilia
 Intermediate between basal amphibians and caecilians An early caecilian Primitive traits
  • Bears three-toed vestigial limbs
  • The size of the orbits indicates well developed eyes and suggest a non-subterranean lifestyle

Derived traits

  • The body has been adapted to a sort of serpentine shape

Read more about this topic:  List Of Transitional Fossils

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