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Ichthyostega (from Greek: ἰχθῦς ikhthûs, 'fish' and Greek: στέγη stégē, 'roof') is an extinct genus of limbed tetrapodomorphs from the Late Devonian of what is now Greenland. It was among the earliest four-limbed vertebrates ever in the fossil record and was one of the first with weight-bearing adaptations for terrestrial locomotion.
The order Ichthyostegalia was erected for Ichthyostega, and contained until the 1980s only three genera (Ichthyostega, Acanthostega and Tulerpeton).While Ichthyostegalia in principle contain the most basal of animals with toes rather than fins, Clack and Ahlberg uses it for all finds more advanced than Tiktaalik (the closest relative of tetrapods known to have retained paired fins rather than ...
This clade is defined as "the node-based clade arising from the most recent common ancestor of Eusthenopteron and Ichthyostega plus all of its descendants," for their litany of shared morphological characteristics, such as similarities in their lower jaws and endocrania. [2]
The geographical range of the Indonesia coelacanth, Latimeria menadoensis, is believed to be off the coast of Manado Tua Island, Sulawesi, Indonesia, in the Celebes Sea. [62] Key components confining coelacanths to these areas are food and temperature restrictions, as well as ecological requirements such as caves and crevices that are well ...
Ichthyostegalia, the primarily aquatic primitive labyrinthodonts such as Acanthostega, Ichthyostega, Tulerpeton, and probably loxommatids. [1] Both Ichthyostegalia and Labyrinthodontia constitute paraphyletic evolutionary grades rather than clades, with amniotes and modern amphibians branching off at some point from the latter.
The oldest near-complete tetrapod fossils, Acanthostega and Ichthyostega, date from the second half of the Fammennian. [56] [57] Although both were essentially four-footed fish, Ichthyostega is the earliest known tetrapod that may have had the ability to pull itself onto land and drag itself forward with its forelimbs. There is no evidence that ...
Stegocephalians include both the modern lineage of limbed vertebrates (the crown group tetrapods, including modern amphibians, reptiles, birds and mammals) as well as a portion of the stem group, the earliest limbed tetrapodomorphs such as Ichthyostega and Acanthostega, which evolved in the Devonian period long before the origin of the crown group.
Until finds of other early tetrapods and closely related fishes in the late 20th century, Ichthyostega stood alone as the transitional fossil between fish and tetrapods, combining a fishlike tail and gills with an amphibian skull and limbs. It possessed lungs and limbs with seven digits that helped it navigate through shallow water in swamps.