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Amphibians like frogs and toads can vocalise using vibrating tissues in airflow. For example, frogs use vocal sacs and an air-recycling system to make sound, while pipid frogs use laryngeal muscles to produce an implosion of air and create clicking noise. [7] Aquatic mammals such as seals and otters can produce sound using the larynx.
The first amphibians appeared on land in the Carboniferous. During the Triassic , mammals and dinosaurs appeared, the latter giving rise to birds in the Jurassic . Extant species are roughly equally divided between fishes of all kinds, and tetrapods.
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.
While the early amniotes resembled their amphibian ancestors in many respects, a key difference was the lack of an otic notch at the back margin of the skull roof. In their ancestors, this notch held a spiracle , an unnecessary structure in an animal without an aquatic larval stage. [ 25 ]
The monotremes, including the semi-aquatic platypus and the terrestrial echidnas, are one of the only groups of mammals that have evolved electroreception. While the electroreceptors in fish and amphibians evolved from mechanosensory lateral line organs, those of monotremes are based on cutaneous glands innervated by trigeminal nerves.
Marine mammals are aquatic mammals that rely on the ocean for their existence. They include animals such as sea lions, whales, dugongs, sea otters and polar bears. Like other aquatic mammals, they do not represent a biological grouping. [26] The humpback whale is a fully aquatic marine mammal.
The resemblance between the crocodilians and phytosaurs in particular is quite striking; even to the point of having evolved the graduation between narrow- and broad-snouted forms, due to differences in diet between particular species in both groups. [88] Death adders strongly resemble true vipers, but are elapids. [89]
Marine mammals that live in coastal environments are the most likely to be affected by habitat degradation and loss. Developments such as sewage marine outfalls, moorings, dredging, blasting, dumping, port construction, hydroelectric projects, and aquaculture both degrade the environment and take up valuable habitat. [47]