Could be a really big flood. Really big floods occur around the world with regularity, and Hidalgo is certainly a place where hurricanes (and ensuing really big floods) have caused significant damage and deaths in the past. Of course we know this isn’t evidence of Noah’s flood; since he gathered two of every animal, we’d still have mammoths, mastodons, and armadillos the size of cars still wandering around.
Believe what you will, I will be very happy in my G_d fearing ignorance. And I believe that G_d will bless me for it.
Well, using that train of thought, no animals must have become extinct since the time of Noah. Including this very short list, I suppose -