held by the Royal Society. It was one of the many bird species originally described by Linnaeus in the landmark 1758 10th edition of his Systema Naturae, and still bears its original scientific name, Phaethon aethereus. The genus name is derived from Ancient Greek phaethon, "sun" while the species name comes from Latin aetherius, "heavenly". This bird is called the red-billed tropicbird due to its red bill and its location in the tropicbird genus. An alternative common name was "bosun bird", also spelt "boatswain bird", from the similarity of its shrill call to a boatswain's whistle. An alternative derivation of the name is from the semblance of the tail feathers to marlin spikes. Local names used in the West Indies include "truphit", "trophic", "white bird", "paille-en-queue", "paille-en-cul", "flèche-en-cul", and "fétu". In a 1945 paper, American ornithologist Waldo Lee McAtee proposed it be called the barred-backed tropicbird after its most distinguishing feature. The red-billed tropicbird is basal (the earliest offshoot) in the genus Phaethon, the sole extant genus in the family Phaethontidae, the tropicbirds. The split between this tropicbird and the other tropicbirds, the red-tailed and white-tailed tropicbird, is thought to have occurred about six million years ago. There are three subspecies, including the nominate, of this tropicbird: Description The red-billed tropicbird measures on average, which includes the -long . Without them the tropicbird measures about . It has a wingspan of . In overall appearance it is tern-like in shape. Its plumage is white, with black wing tips, and a back that is finely barred in black. It has a black mask that extends up from just above the lores to the sides of its nape, with gray mottling usually seen near the nape and hindneck. The tail has black shaft streaks, as do tail streamers. The are white, with some black on the outermost primaries and tertials and occasionally with black markings on the flanks. The iris is blackish-brown, and the bill is red. The legs, base of the central toe, and parts of the outer toes are orange-yellow while the rest of the feet are black. Although the sexes are similar, the males are generally larger than females, with the tail streamers being around longer on the male than on the female. The subspecies of this bird can usually be distinguished by their difference in size and plumage. The subspecies Phaethon aethereus mesonauta can be differentiated by its