Ivory gull narrower os pubis, and potentially more flexibility in skull kinetic structure. Structurally, it is most similar to the kittiwakes; however, recent genetic analysis based on mtDNA sequences shows that Sabine's gull is the ivory gull's closest relative, followed by the kittiwakes, with Ross's gull and swallow-tailed gull sharing a clade with these species. "Pagophila" is maintained as a unique genus because of the bird’s morphological, behavioral and ecological differences from these species. Colloquial names from Newfoundland include slob gull (from "slob", a local name for drift ice) and ice partridge, from a vague resemblance to a ptarmigan. This species is
Gull-wing door a precursor, but is often overlooked when discussing gull-wing design. Conventional car doors are typically hinged at the front-facing edge of the door, with the door swinging outward horizontally. Apart from the Mercedes-Benz 300SL of the mid-1950s and the experimental Mercedes-Benz C111 of the early 1970s, the best-known examples of road-cars with gull-wing doors are the Bricklin SV-1 from the 1970s, the DeLorean DMC-12 from the 1980s, and the Tesla Model X of the 2010s. Gull-wing doors have also been used in aircraft designs, such as the four-seat single-engine Socata TB series built in France. The design is a very