As a rule all mammals have the same number of vertebrae in their necks regardless of whether they are a giraffe, a mouse, or a human. But
As a rule all mammals have the same number of vertebrae in their necks regardless of whether they are a giraffe, a mouse, or a human. Butboth sloths and manatees are exceptions to this rule having abnormal numbers of cervical vertebrae. New research published in BioMed Central's open access journalEvoDevoshows how such different species have evolved their unusual necks.
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Birds, reptiles and amphibians have varying number of vertebrae in their necks, swans have 22-25, but mammals, regardless of size of animalor the animal's neck, only have seven. Aberrant neck vertebrae are usually correlated with an increase in risk of stillbirth, childhood cancer and neuronal problems in mammals. These pleiotropic events are often associated with physical problems, such as thoracic outlet syndrome, due to misplaced or crushed nerves, muscles and blo