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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 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.
The history of paleontology traces the history of the effort to understand the history of life on Earth by studying the fossil record left behind by living organisms. Since it is concerned with understanding living organisms of the past, paleontology can be considered to be a field of biology, but its historical development has been closely tied to geology and the effort to understand the ...
The world's smallest known vertebrate, Paedophryne amauensis, sitting on a U.S. dime.The dime is 17.9 mm in diameter, for scale. The word amphibian is derived from the Ancient Greek term ἀμφίβιος (amphíbios), which means 'both kinds of life', ἀμφί meaning 'of both kinds' and βίος meaning 'life'.
Animals form a clade, meaning that they arose from a single common ancestor. Over 1.5 million living animal species have been described, of which around 1.05 million are insects, over 85,000 are molluscs, and around 65,000 are vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth.
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).
New animals appeared in the warmer, drier regions near the equator as four-legged vertebrates called stem tetrapods evolved and split into groups that formed the basis for modern animals.
Vertebrate paleontology is the subfield of paleontology that seeks to discover, through the study of fossilized remains, the behavior, reproduction and appearance of extinct vertebrates (animals with vertebrae and their descendants).