The average dog has 26 vertebrae. 7 cervical, 13 thoracic, and 6 lumbar. Some breeds such as the English Bulldog may frequently have a 7th lumbar vertebra, or a portion of a vertebra called a transitional vertebra.

The anatomy books show what are normally seen, five vertebra... There are many variants in anatomy, and someone with four lumbar vertebras isn't abnormal, just someone who is a little different, but still normal. You might have something we call a "transitional" vertebra, such as an extra thoracic vertebra merged into a lumbar, or maybe a lumbar vertebra fused with a sacral vertebra... Still normal...

Transitional vertebra - A vertebra that takes on the characteristic of the vertebra on either side of it.

· Example a cervical vertebra with a rib attached

Spina Bifida -A posterior defect of the spinal canal resulting from failure of the posterior elements to fuse properly

Osteopetrosis "Marble Bone"- There in an increase in bone resorption

Osteogenesis imperfecta - "Brittle Bone Disease"

· The skeleton does not ossify properly.

· Often characterized by a blue coloration of the white sclera of the eye

Acondroplasia - Failure of cartilage that becomes bone to form properly. Causes dwarfism

A kangaroo is a vertebra.

Cervical vertebra