The neural crest is a uniquely vertebrate cell type that is thought to have played an important role in vertebrate evolution by forming peripheral ganglia and jaws, thus facilitating predation and expansion of the brain. In the parent grant, we are testing the hypothesis that there was progressive expansion of neural crest derivatives during the course of vertebrate evolution. As case in point, lamprey lack a vagal neural crest that in gnathostomes forms the enteric nervous system. To further understand the evolution of the enteric nervous system in basal vertebrates, in this supplement we propose to examine the complexity of the lamprey ENS in comparison to other vertebrates to gain insight into elaboration of the enteric nervous system in the vertebrate lineage. To explore this, we propose to transcriptionally profile lamprey ENS both by single cell RNA-seq and spatial transcriptomics to enable comparison with the ENS of jawed vertebrates. The results promise to elucidate how new cell types arose during vertebrate evolution under the umbrella of the neural crest.