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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).
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.
Marine tetrapod (sperm whale) Internal skeletal structures showing the vertebral column running from the head to the tail Marine vertebrates are vertebrates that live in marine environments , which include saltwater fish (including pelagic , coral and deep sea fish ) and marine tetrapods (primarily marine mammals and marine reptiles , as well ...
Whales are fully aquatic, open-ocean animals: they can feed, mate, give birth, suckle and raise their young at sea. Whales range in size from the 2.6 metres (8.5 ft) and 135 kilograms (298 lb) dwarf sperm whale to the 29.9 metres (98 ft) and 190 tonnes (210 short tons) blue whale, which is the
The distinction between quadrupeds and tetrapods is important in evolutionary biology, particularly in the context of tetrapods whose limbs have adapted to other roles (e.g., hands in the case of humans, wings in the case of birds and bats, and fins in the case of whales). All of these animals are tetrapods, but not all are quadrupeds.
It was the ancestor of modern whales, dolphins, and porpoises. The cetacea are extensively adapted to marine life and cannot survive on land at all. Their adaptation can be seen in many unique physiognomic characteristics such as the dorsal blowhole , baleen teeth, and the cranial 'melon' organ used for aquatic echolocation .
WELLINGTON, New Zealand (AP) — It is the world’s rarest whale, with only seven of its kind ever spotted.Almost nothing is known about the enigmatic species. But on Monday a small group of scientists and cultural experts in New Zealand clustered around a near-perfectly preserved spade-toothed whale hoping to decode decades of mystery.
Parvorder Mysticeti (Baleen whales) Family Balaenidae (right and bowhead whales) Family Cetotheriidae (pygmy right whale) Family Eschrichtiidae (gray whale) Family Balaenopteridae (rorquals) Parvorder Odontoceti (Toothed whales) Family Physeteridae (sperm whale) Family Kogiidae (pygmy and dwarf sperm whales) Family Ziphiidae (beaked whales)