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Figure 1:In mammals, the quadrate and articular bones are small and part of the middle ear; the lower jaw consists only of dentary bone.. While living mammal species can be identified by the presence of milk-producing mammary glands in the females, other features are required when classifying fossils, because mammary glands and other soft-tissue features are not visible in fossils.
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.
Synapsida [a] is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant reptiles and birds).
Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny [ 1 ] (the evolution of species). The science began in the classical era , continuing in the early modern period with work by Pierre Belon who noted the similarities of the skeletons ...
A major difference between early tetrapodomorph fishes and early tetrapods was in the relative development of the front and back skull portions; the snout is much less developed than in most early tetrapods and the post-orbital skull is exceptionally longer than an amphibian's. A notable characteristic that make a tetrapod's skull different ...
Class Mammalia (mammals) Subclass Prototheria (Monotremata, egg-laying mammals) Subclass Theria (metatheria (such as marsupials) and eutheria (such as placental mammals)) This rather orderly scheme is the one most commonly found in popular and basic scientific works.
The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus) [41] but this is a great deal smaller than the largest amphibian that ever existed—the extinct 9 m (30 ft) Prionosuchus, a crocodile-like temnospondyl dating to 270 million years ago from the middle Permian of Brazil. [42]
A = Anapsid, B = Synapsid, C = Diapsid. It was traditionally assumed that first reptiles were anapsids, having a solid skull with holes only for the nose, eyes, spinal cord, etc.; [10] the discoveries of synapsid-like openings in the skull roof of the skulls of several members of Parareptilia, including lanthanosuchoids, millerettids, bolosaurids, some nycteroleterids, some procolophonoids and ...