Sense 2 (“long extinct”) is from the fact that such animals and plants were originally believed to have perished in the biblical flood referred to above.[1]
[P]erhaps ſome perſons might outlive Methuſelah; the Text intending onely the maſculine line of Seth, conduceable unto the Genealogy of our Saviour, and the antediluvian Chronology.
1727, [Daniel Defoe], “Of what Shapes the Devil Assum’d in His First Appearances to the Magicians, and Others, in the First Ages of the World; and whether He is, or has been,, Allow’d to Assume a Human Shape, or No”, in A System of Magick; or, A History of the Black Art.[…], London: […] J. Roberts[…], →OCLC, page 95:
For Noah, vvho had no doubt preach'd againſt the Vices of the Antediluvian VVorld, and againſt Drunkenneſs among the reſt, muſt certainly knovv the Uſe of the Vine, and the Abuſe of it too; hovv elſe did he come to plant it at all, and to preſs the Juice out for Drinking it at all?
The great Egyptian age is but a remnant of the Atlantean culture / The antediluvian kings colonized the world / All the gods who play in the mythological dramas / In all legends from all lands were from fair Atlantis
Having already described him [the whale] in most of his present habitatory and anatomical peculiarities, it now remains to magnify him in an archæological, fossiliferous, and antediluvian point of view.
[H]is eldest son Bo-bo, […] let some sparks escape into a bundle of straw, which kindling quickly, spread the conflagration over every part of their poor mansion, till it was reduced to ashes. Together with the cottage (a sorry antediluvian make-shift of a building, you may think it), what was of much more importance, a fine litter of new-farrowed pigs, no less than nine in number, perished.
There was an antediluvian tradition (much older than Shakespeare) that on Midsummer's Night young people should go with lanterns, and a fiddler, and a keg or two of cider, to a patch of turf known as Donkey's Green in the heart of the woods and there celebrate the solstice with dancing.
The air inside smelled antediluvian, regal somehow, with traces of pipe tobacco, tea leaves, cooking sherry, and the earthen aroma of stone architecture.
2010, Sam Chaltain, “Connect (or, Make the Connections that Let You ‘See the Whole Board’)”, in American Schools: The Art of Creating a Democratic Learning Community, Lanham, Md.: Rowman & Littlefield Education, →ISBN, page 41:
If we agree with [Alan] Blinder's assessment, we must acknowledge the pressing need to inject new ideas into an old system—a system so antediluvian that it is, remarkably, still based on the agrarian calendar.
If, by any miſchance, and in an evil hour, ſome country couſin, not knovving my vvays, or ſome antediluvian prig, not minding them, happen to fall upon me vvith formal ſpeeches, vvhere I can make no eſcape, a fit of yavvning takes me immediately, and I am demoliſhed for the reſt of the day.
2021 December 3, “LGBTQ Couples, Families and Marriage are ‘against the Natural Order,’ Thai Constitutional Court Rules”, in Coconuts Bangkok[1], Bangkok, Thailand: Coconuts Media, archived from the original on 2023-03-19:
Portions of the ruling reflected the court's culturally conservative roots, stating that because marriage is only for reproduction, LGBTQ relationships are unnatural because they cannot produce children. […] The ruling continued in its surprisingly antediluvian rationale, invalidating untold numbers of nontraditional families.