Taxonomy: Currently Thalasseus sandvicensis includes 3 subspecies:

Thalasseus s. sandvicensis (Latham, 1787) for Europe and Africa.
Thalasseus s. acuflavida (Cabot, 1847) for North America, Central America, and South America.
Thalasseus s. eurygnatha (Saunders, 1876) for South America.

Efe et al. (2009) conducted molecular studies concluding that the Old World and New World populations differ genetically as much as other species within the genus. Furthermore, they mention that both American subspecies are so closely related that they do not warrant being considered distinct taxa. They propose:

Thalasseus sandvicensis (Latham, 1787) for the Old World.
Thalasseus acuflavidus (Cabot, 1847) for the Americas, with T. eurygnathus (Saunders, 1876) being a junior synonym.

Savigny (2021) is not recognized as a taxonomic authority (pers. comm.), and provisionally treats three taxa:

Thalasseus sandvicensis (Latham, 1787) for the Old World.
T. a. acuflavidus (Cabot, 1847) for North America, Central America, and South America.
T. a. [eurygnathus] (Saunders, 1876) for South America.

Acknowledgments to Christian Savigny and Cayetano Bernardo Paletta for their contributions and exchanges.

Author of this compilation: Jorge La Grotteria - 01/07/2021.

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