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An ancient synapsid, Dimetrodon, had extremely long spines on its backbone that were joined together with a web of skin that formed a sail-like structure. Many mammalian species, like cats and fossas, [1] [2] also have penile spines. The Mesozoic eutriconodont mammal Spinolestes already displayed spines similar to those of modern spiny mice. [3]
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.
Each vertebra has a facet on each side of the vertebral body, which articulates with the head of a rib. There is also a facet on each of the transverse processes which articulates with the tubercle of a rib. The number of thoracic vertebrae varies considerably across the species. [31] Most marsupials have thirteen, but koalas only have eleven. [32]
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
The animal's spine has bony projections that mesh to form a strong yet flexible backbone. [4] The differences are especially pronounced in the lower back between the rib cage and hips. [ 5 ] The hero shrew has 11 lumbar vertebrae , in contrast to a typical mammal which has 5 such vertebrae.
Marine vertebrates also have a far more centralized nervous system than marine invertebrates, with most of the higher functions cephalized and monopolized by the brain; and most of them have evolved myelinated central and peripheral nerve system, which increases conduction speeds significantly.
Vertebrate zoology is the biological discipline that consists of the study of Vertebrate animals, i.e., animals with a backbone, such as fish, amphibians, reptiles, birds and mammals. Many natural history museums have departments named Vertebrate Zoology .