Crymostygius thingvallensis is a species of subterranean amphipod crustacean, endemic to the area around Þingvallavatn, a lake in southwestern Iceland. The species has no close relatives, and is placed in its own family, Crymostygidae. This distinctness has been confirmed by molecular phylogenetics.
Species taxanomy provided by GBIF Secretariat (2022). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on 2023-06-13; License: CC BY 4.0