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Evolutionary theory says all animals that are walking on land actually evolved from sea-dwelling creatures at some point in the ancient past. To study this further, scientists from McGill ...
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.
Insects roamed the land and would soon take to the skies; sharks swam the oceans as top predators, [83] and vegetation covered the land, with seed-bearing plants and forests soon to flourish. Four-limbed tetrapods gradually gain adaptations which will help them occupy a terrestrial life-habit. 360 Ma First crabs and ferns.
In walking, and for many animals running, the motion of legs on either side of the body alternates, i.e. is out of phase. Other animals, such as a horse when galloping, or an inchworm, alternate between their front and back legs. In saltation (hopping) all legs move together, instead of alternating. As a main means of locomotion, this is ...
Either way, the name refers to the loon's poor ability to walk on land. [17] Another possible derivation is from the Norwegian word lom for these birds, which comes from Old Norse lómr, possibly cognate with English "lament", referring to the characteristic plaintive sound of the loon. [18] The scientific name Gavia refers to seabirds in ...
Acanthostega (meaning "spiny roof" in Ancient Greek) is an extinct genus of stem-tetrapod, among the first vertebrate animals to have recognizable limbs.It appeared in the late Devonian period (Famennian age) about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and those that were fully capable of coming onto land.
Despite eurypterids clearly being primarily aquatic animals that almost certainly evolved underwater (some eurypterids, such as the pterygotids, would even have been physically unable to walk on land), it is unlikely the "gill tract" contained functional gills when comparing the organ to gills in other invertebrates and even fish.
List of extinct animals of Romania; List of fossil species in the La Brea Tar Pits, California, United States; List of fossil species in the London Clay, England; List of White Sea biota species by phylum, Russia; Paleobiota of the Hell Creek Formation, northern United States; Paleobiota of the Morrison Formation, western United States