This species is closely similar to Dynamene bidentata, but males can be distinguished by the shape of the two backwards projections, which in D. magnitorata maintain a similar width along their length but which taper in D. bidentata. In addition, the two halves of the pleotelsonic boss are separated by a narrow groove, whilst in D. bidentata they are separated by a wide v-shaped groove. Males up to 6.0mm, females up to 4.8mm.
This species occurs around the Channel Islands, whilst a single record from Dorset on the southern English coast may represent a stranding (Vieira et al. 2016). Found in similar habitats to D. bidentata, from MTL to the sublittoral.
Hayward, Peter & John Ryland. 2017. Handbook of the Marine Fauna of North-west Europe (2nd Edition). Oxford: Oxford University Press.
Vieira, Pedro E., Henrique Queiroga, Filipe O. Costa, David M. Holdich. 2016. Distribution and species identification in the crustacean isopod genus Dynamene Leach, 1814 along the North East Atlantic-Black Sea axis. ZooKeys 635, 1–29.