The notochord is unconstricted, but the neural and haemal arches are well-developed, and the neural spines are long and slender.
The ventral arcualia become, in the tail region only, also incorporated in complete arches—the haemal arches.
This is the vascular or haemal system (formerly and unnecessarily termed pseudhaemal).
The haemal spines of the turned-up tip of the tail are flattened (hypural bones) and serve to support the caudal fin rays.
Further back still, towards the hind end of the tail, the haemal arches bear median haemal spines (ventrispinalia).
haemal arches similar to the neural arches are often found as in Urodela.
The neural and haemal arches and spines are cartilaginous and interbasalia (intercalary pieces) are present.
Both neural and haemal arches are ossified continuously with the centra.
In Dipnoi these interspinous bones articulate with the neural and haemal spines.
All are of the coelacanth type, having Y-shaped neural and haemal arches, without centra.