Explain in brief the divisions of sub-phylum Vertebrata.

Sub-phylum vertebrata is divided into two divisions:

Agnathostomata (lacks jaw) and Gnathostomata (bears jaw) on the basis of presence/absence of jaws. 

1. Division Agnathostomata: 

This division consist of the lowest or most primitive vertebrates that lack jaws. 

They include only one class of living vertebrates, the Cyclostomata.

2. Division Gnathostomata: 

This division includes animals with jaws. 

It is divided into two superclasses: 

Pisces (bear fins) and Tetrapoda (bear four limbs) 

[Note: Students can scan the given Q.R code for understanding the characteristics of vertebrates.]