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Vertebrates (/ ˈ v ɜːr t ə b r ɪ t s,-ˌ b r eɪ t s /) [3] are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest ...
The foot (pl.: feet) is an anatomical structure found in many vertebrates.It is the terminal portion of a limb which bears weight and allows locomotion.In many animals with feet, the foot is a separate [clarification needed] organ at the terminal part of the leg made up of one or more segments or bones, generally including claws and/or nails.
A clade is by definition monophyletic, meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. [ note 1 ] [ 10 ] [ 11 ] The ancestor can be known or unknown; any and all members of a clade can be extant or extinct.
A majority of paleontologists use the term "tetrapod" to refer to all vertebrates with four limbs and distinct digits (fingers and toes), as well as legless vertebrates with limbed ancestors. [ 15 ] [ 16 ] Limbs and digits are major apomorphies (newly evolved traits) which define tetrapods, though they are far from the only skeletal or ...
The appearance of the early vertebrate jaw has been described as "a crucial innovation" [25] and "perhaps the most profound and radical evolutionary step in the vertebrate history". [ 26 ] [ 27 ] Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct during the Triassic period.
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).
A forelimb or front limb is one of the paired articulated appendages attached on the cranial end of a terrestrial tetrapod vertebrate's torso. With reference to quadrupeds, the term foreleg or front leg is often used instead. In bipedal animals with an upright posture (e.g. humans and some other primates), the term upper limb is often used.
Birds are a group of warm-blooded vertebrates constituting the class Aves (Latin:), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.