the answer is the sacrum
I believe what you are talking about is the sacrum? It's just below the spine in the pelvic area..
The sacrum, which consists of 5 fused bones, and the coccyx are below the lumbar vertebrae in the spine.
The sacral bone is a large, triangular bone at the base of the spine that forms the back of the pelvis. It is made up of five fused vertebrae and connects the spine to the hip bones. The sacrum plays an important role in providing structural support and stability to the spine and pelvis.
The top 5 major bones are the:The Cranium (skull)The mandible (lower jaw)Vertebral column (spine)Sternum (breast bone)Ribs
The bones below the sacrum are called the coccyx, also known as the tailbone. It is located at the base of the spinal column and consists of three to five fused vertebrae. It serves as an attachment point for muscles and ligaments.
The bone that forms the back bone is the spine. The spine is composed of vertebrae. It is the chief support of organizing the nervous system.
about 8 bone
The lumbar vertebrae in the lower back is typically five in number and unfused.
The pelvis connects them.
Your "backbone" is actually a series of bones; the technical name is "spinal column", and it's a stack of bones called "vertebrae" connected by cartilage and muscles that allow it to bend and twist. At the bottom of the spine, the vertibrae connect to the pelvis, or "hip bones", which then connect to the thigh, the upper leg bones. The lowermost bone in the spine is the coccyx, or tailbone. If we had tails, that's where they would be connected.
The Spine is made up of many smaller bones, which is what allows flexing and movement of the spine. Please see the related links for a detailed picture of the bones that make up the spine.
There are 122 bones in a dog's spine.