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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.
Acanthostega is a partially aquatic tetrapod with developed limbs that shares features common with the earlier tetrapods, Panderichthys and Eusthenopteron. [3] Like Panderichthys , the humerus of Acanthostega is flattened dorso-ventrally, the intermedium terminates level with the radius, and the endoskeleton can be divided into stylopodium ...
Traditionally, Ichthyostega was considered part of an order named for it, the "Ichthyostegalia". However, this group represents a paraphyletic grade of primitive stem-tetrapods and is not used by many modern researchers. Phylogenetic analysis has shown Ichthyostega is intermediate between other primitive stegocephalian stem-tetrapods. The ...
Early humans were social and initially scavenged, before becoming active hunters. The need to communicate and hunt prey efficiently in a new, fluctuating environment (where the locations of resources need to be memorized and told) may have driven the expansion of the brain from 2 to 0.8 Ma. Evolution of dark skin at about 1.2 Ma. [39]
Thus there was in the evolution of tetrapods a shift such that the outermost part of the fins were lost and eventually replaced by early digits. This change is consistent with additional evidence from the study of actinopterygians , sharks and lungfish that the digits of tetrapods arose from pre-existing distal radials present in more primitive ...
Kenichthys is important to the study of the evolution of tetrapods due to the nature of its nostrils. Most non-tetrapod vertebrates (e.g. actinopterygians) possess two sets of nostrils, one set at either end of the nasal cavity, and both sets of which are external. These nostrils play no part in respiration, instead serving an olfactory role.
The former CEO of Abercrombie & Fitch (A&F) has dementia and late onset Alzheimer's disease, his legal team has said in a court document filed in New York. Lawyers for Mike Jeffries have requested ...
In effect, "tetrapod" is a name reserved solely for animals which lie among living tetrapods, so-called crown tetrapods. This is a node-based clade , a group with a common ancestry descended from a single "node" (the node being the nearest common ancestor of living species).