The endosymbiosis between an alga and the spotted salamander shows several parallels to invertebrate-algal symbioses as well as to pathogen associations in vertebrate animals.
Elizabeth M Sefton, Bhart-Anjan S Bhullar ... James Hanken
Both gill musculature and the evolutionarily conserved cucullaris muscle are derived from unsegmented mesoderm adjacent to the first 3 somites, extending the posterior limit of cranial mesoderm.