The holeospondile vertebras are grouped in 2 main groups: intrachordale (chordacentric) and perichordale (acrocentric)
The intrachordale vertebra is characteristic to selaciens. It’s formed through the migration of the mezenchim cells from the arcuali base, the perforation of the elastic membrain extern and their disposition in the fibrous notocord steath. It than transforms into cartilaginous tisue wich extends and gathers the elastic extern membrain wich is integrated forming a cartilaginous piece with a ring aspect wich surounds the chordal tisue of the notocord. In the end, the vertebral body fusiones with the neural arc and the hemal arc forming an unic cartilaginous piece.
The perichordal is prezent at teleosteeni and the entire vertebrate series. The mezenchim cells from the arcual base migrate and are disposed around the fibrous steath without perforing the membrain. It ossifies and forms a vertebral body wich strangulates the notocord so that it gets a monoliform aspect like a strand of beads. Later the vertebral body fusions with the hemal and neural arc forming an unic piece.
