When did Xiphactinus cease to exist following the K–Pg extinction event?
Answer
Around 66 million years ago.
The evolutionary context provided places *Xiphactinus* firmly as a successful organism spanning the mid-to-late Cretaceous period. Its lineage was ultimately terminated by the catastrophic global environmental change known as the K–Pg extinction event. This boundary event is precisely dated by geological and paleontological evidence as occurring around 66 million years ago, marking the end of the Cretaceous period and the demise of non-avian dinosaurs and many large marine reptiles and fishes, including this large piscivore.
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