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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.
A mammal (from Latin mamma 'breast') [1] is a vertebrate animal of the class Mammalia (/ m ə ˈ m eɪ l i. ə /). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones.
An evolutionary tree (of Amniota, for example, the last common ancestor of mammals and reptiles, and all its descendants) illustrates the initial conditions causing evolutionary patterns of similarity (e.g., all Amniotes produce an egg that possesses the amnios) and the patterns of divergence amongst lineages (e.g., mammals and reptiles ...
Pelycosaur (/ ˈ p ɛ l ɪ k ə ˌ s ɔːr / PEL-ih-kə-sor) [1] is an older term for basal or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term mammal-like reptile had been used, [2] and pelycosaur was considered an order, but this is now thought to be incorrect and outdated.
Evolution of dinosaurs – Archosaurian reptiles that dominated the Mesozoic Era. Evolution of birds – Derivation of birds from a dinosaur precursor; Evolution of mammals – Derivation of mammals from a synapsid precursor, and the adaptive radiation of mammal species Evolution of cetaceans
The terms reptile and amphibian were largely interchangeable, reptile (from Latin repere, 'to creep') being preferred by the French. [9] J.N. Laurenti was the first to formally use the term Reptilia for an expanded selection of reptiles and amphibians basically similar to that of Linnaeus. [10]
Basal non-mammalian synapsids ("mammal-like reptiles") traditionally also sort under class Reptilia as a separate subclass, [27] but they are more closely related to mammals than to living reptiles. Considerations like these have led some authors to argue for a new classification based purely on phylogeny , disregarding the anatomy and physiology.
The three small bones in the middle ear of mammals including humans, the malleus, incus, and stapes, are today used to transmit sound from the eardrum to the inner ear. The malleus and incus develop in the embryo from structures that form jaw bones (the quadrate and the articular) in lizards, and in fossils of lizard-like ancestors of mammals.