The Sinking of Another Tristan da Cunha Moss Endemic and Its Phytogeographical Consequences

The original material of Isopterygium tristaniense Dixon, an endemic species of the Tristan da Cunha archipelago in the central South Atlantic Ocean, is taxonomically evaluated and some details of its morphology are illustrated. The species is found to be conspecific with the Holarctic Pseudotaxiphyllum elegans (Brid.) Z. Iwats. and this is the third record of the species in the Southern Hemisphere. The global distribution of this species is reviewed, and the distribution patterns of the South Atlantic mosses are briefly discussed.