Congratulations on elucidating these linear mitogenomes! I am so relieved to read this. Approximately 14 years ago, Scott France and I proposed that the cerianthid mitogenome was linear here:
Brugler, M.R., 2004. The complete mitochondrial DNA sequence of the black coral Chrysopathes formosa (Antipatharia) and six non-contiguous mitochondrial genes of the tube anemone Ceriantheopsis americanus (Ceriantharia): implications for cnidarian phylogeny (Masters Thesis, Graduate School of the College of Charleston).
In this work, we were able to sequence ...nad1-IGR-cox1-cox2... as well as ...12S-IGR-16S... and ...nad6-IGR-16S... (the dots indicate long "telomere-like" non-coding regions)
We reported a subset of this data in the following paper (see Fig. 4B):
Brugler, M.R. and France, S.C., 2007. The complete mitochondrial genome of the black coral Chrysopathes formosa (Cnidaria: Anthozoa: Antipatharia) supports classification of antipatharians within the subclass Hexacorallia. Molecular Phylogenetics and Evolution, 42(3), pp.776-788.
You can access the genetic data for Ceriantheopsis americana here:
GenBank Accessions Numbers DQ662399 and DQ662400
The reviewers would not allow us to speculate that the cerianthid mitogenome was linear, so we had to settle with the following: "...it is apparent that gene order will be quite different from both the Antipatharia and the other published anthozoan mitochondrial genomes, and, therefore, the Ceriantharia may merit separate subclass status."
Again, congratulations! This is an impressive contribution to the field of mitogenomics as well as our understanding of the evolution of the Anthozoa. Keep up the good work!
-Mercer R. Brugler