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For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; a group of amphibians, the labyrinthodonts, have given rise to the reptiles (traditionally including the mammal-like synapsids), which in ...
Palatal and nasal skeletal features like choanae are present in these groups and are also observed in modern amphibians. This indicates that incipient air breathing was developed, as well as modification of the hyoid arch towards stapes development. [5] These characteristics account for why osteichthyans are accepted as the sister group of ...
The earliest mammals were generally small animals, and were likely nocturnal insectivores. This suggests a plausible source of evolutionary pressure: with these small bones in the middle ear, a mammal has extended its range of hearing for higher-pitched sounds which would improve the detection of insects in the dark. [34]
The legs of tetrapods, the main group of terrestrial vertebrates (which also includes amphibious fish), have internal bones, with externally attached muscles for movement, and the basic form has three key joints: the shoulder joint, the knee joint, and the ankle joint, at which the foot is attached. Within this form there is much variation in ...
Their diet varies considerably as well: some may eat zooplankton; others may eat fish, squid, shellfish, and sea-grass; and a few may eat other mammals. In a process of convergent evolution, marine mammals such as dolphins and whales redeveloped their body plan to parallel the streamlined fusiform body plan of pelagic fish.
Ape skeletons. A display at the Museum of Zoology, University of Cambridge.From left to right: Bornean orangutan, two western gorillas, chimpanzee, human. The evolution of human bipedalism, which began in primates approximately four million years ago, [1] or as early as seven million years ago with Sahelanthropus, [2] [3] or approximately twelve million years ago with Danuvius guggenmosi, has ...
The world’s frogs, salamanders, newts and other amphibians remain in serious trouble. A new global assessment has found that 41% of amphibian species that scientists have studied are threatened ...
A skeleton is the structural frame that supports the body of most animals.There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal frame to which the organs and soft tissues attach; and the hydroskeleton, a flexible internal structure supported by the hydrostatic pressure of body fluids.