Caudal vertebrae [Coccygeal]

Antoine Micheau

The caudal or coccygeal vertebrae reduce in size gradually, with a graduate simplification of their form (losing arches and processes, and with a simple cylindrical shape at the end). On the ventral surfaces of caudal vertebrae in ruminants (Cd1 to 8) and carnivores (Cd 5 to 15), are paramedian processes, the hemal processes, for the protection of caudal vessels. These hemal processes sometimes fuse to form the hemal arches (ox: Cd 2-3, carnivores CD 3 to 8).

The number of caudal vertebrae differs between species:

Species/Group	Caudal Vertebrae Count
Human	3–5 (fused coccyx)
Dog	20–23
Cat	18–23
Horse	15–21
Cow	18–20
Pig	20–23
Elephant	26–33
Lizard	20–50+
Snake	20–40 (caudal)
Salamander	30–60
Bird (e.g., pigeon)	5–9 + pygostyle