Sea anemones possess dynamic mitogenome structures.

Highlights: [•] We present genomic resources of cold-water sea anemones. [•] An obligatory group I intron contains truncated duplicated gene sequences. [•] A mobile group I intron contains an expressed homing endonuclease gene. [•] We detect a novel insertion element that contains expressed protein coding genes. [•] Introns and insertion element have higher substitution rates. [Copyright &y& Elsevier]