The three gannet
species are now usually placed in the genus
Morus,
Abbott's booby in
Papasula, and the remaining boobies in
Sula. However, some authorities believe that all nine sulid species should be considered congeneric, in
Sula. At one time, the various gannet species were considered to be a single species. in
Bonaventure Island's colony Most fossil gannets are from the Late
Miocene or
Pliocene, when the diversity of
seabirds in general was much higher than today. The cause of the decline in species at the end of the Pleistocene is not clear; increased competition due to the spread of
marine mammals may have played a role. The genus
Morus is much better documented in the
fossil record than
Sula, though the latter is more numerous today. The reasons are not clear; boobies possibly were better adapted or simply "lucky" to occur in the right places for dealing with the challenges of the Late Pliocene ecological change, or many more fossil boobies could still await discovery. Notably, gannets are today restricted to temperate oceans, while boobies are also found in tropical waters, whereas several of the prehistoric gannet species had a more
equatorial distribution than their congeners of today. Fossil species of gannets are: •
Morus loxostylus (Early Miocene of EC USA) – includes
M. atlanticus •
Morus olsoni (Middle Miocene of Romania) •
Morus lompocanus (Lompoc Late Miocene of Lompoc, USA) •
Morus magnus (Late Miocene of California) •
Morus peruvianus (Pisco Late Miocene of Peru) •
Morus vagabundus (Temblor Late Miocene of California) •
Morus willetti (Late Miocene of California) – formerly in
Sula •
Morus sp. (Temblor Late Miocene of Sharktooth Hill, US: Miller 1961) – possibly
M. magnus •
Morus sp. 1 (Late Miocene/Early Pliocene of Lee Creek Mine, US) •
Morus sp. 2 (Late Miocene/Early Pliocene of Lee Creek Mine, US) •
Morus peninsularis (Early Pliocene) •
Morus recentior (Middle Pliocene of California, US) •
Morus reyanus –
Del Rey gannet (Late Pleistocene of W US) ==Cultural references==