Abstract
Here, we sequenced and annotated the complete mitochondrial genome for the sea-pen, Cavernularia obesa (Valenciennes, 1850). The complete mitogenome of C. obesa is 18,641 bp, with 34.7% of GC ratio. The mitogenome comprises 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a non-coding region. Phylogenomic analysis based on 19 in-group taxa belonging to the orders Alcyonacea and Pennatulacea has congruent with published phylogenetic relationship for Octocorallia, which C. obesa was grouped to members of the Pennatulacea. This mitogenome resource will be useful for future phylogenetic studies of water fleas.