Heredity (Edinb). 2008 Oct;101(4):301-20. doi:10.1038/hdy.2008.62

Gissi C, Iannelli F, Pesole G.

Evolution of the mitochondrial genome of Metazoa as exemplified by comparison of congeneric species.

Mitochondrial genomes of tunicates have all genes colinear on the same strand, and usually encode 24 tRNAs (instead of 22 in vertebrates). Their rRNA genes are separated.