Until then, the most recent traces of such a creature had been in rocks dating from the last days of the dinosaurs, 65m years ago.
Tellingly, these works date from the mid-1990s, before the Chinese art boom began heating up, while the others date from the last few years.
It is a big show, titled "Home," with more than 45 works, most dating from the last couple of years, spread over three rooms.
In a secret program called "Olympic Games," which dates from the last years of the George W. Bush administration, the United States has mounted repeated attacks with the most sophisticated cyberweapons ever developed.
While they date from the last 20 years, their animating spirit is Post-Minimalist 1970s, when Ms. von Rydingsvard was in her 30s and had earned a master's degree in fine arts at Columbia University.
Most of them date from the last few years and focus on floral bouquets, usually set on windowsills overlooking city or country vistas in ways that mix aspects of still life, landscape and to some extent portraiture.
The natural history display cases, which will remain for at least a few years, are so quaintly old-fashioned that they have more impact than the more discursive and graphic displays dating from the last renovation.
The Davis show is the most full-bodied of the lot, a greatest-hits lineup of 16 paintings, most of them museum loans, dating from the last two decades of his energetic career.
Since 1998, when Christie's separated postwar art (works made from 1945 to the late 1960's) from what it defines as contemporary art (works dating from the last 35 years), it has brought young artists out of the galleries and into the auction house.
In his brief career (all his extant paintings date from the last five years of his life) this highly inventive young artist taught his contemporaries and successors how to exploit the medium of oil paint to create the illusion of textures, light, and air in their paintings.
Most (88.5%) was published between 2005 and 2015, and only two studies date from the last century.
